Long Crank/Hard Start

[93formulalt1]

So the saga continues. . .

Here's the deal. 1994 LT1/T56 Formula, just fixed a backfire/running rough issue, replaced the following:

-Optispark
-Spark Plugs (NGK TR55GP @ .045")
-Spark Plug Wires (BWD Spiral Core)
-Timing Set
-Ignition Coil (BWD Select)
-Water Pump
-Fuel Pump
-Fuel Filter
-Header Gaskets (No exhaust leaks anywhere now)
-O2 Sensors (Both upstream, OE-type Bosch, reading properly)


The problem I'm having now, it's taking about 5-8 seconds of cranking to get it to start. When it does start, depending on outside temperature, it idles funny (if cold, it idles high, around 1500RPM, then drops to 700-800 after 15-30 seconds of idling). Usually, when it's warm outside, it'll idle high (~1200RPM, drops after 5-10 seconds to 700-800), but sometimes, it will "search" for idle speed, nearly dying out when stopping for a traffic light, idling at ~500RPM until the car stops, then it will increase to the proper idle speed.

Sometimes, I can't get it to start on the first try, but it will start on the 2nd try. It's always started, never breaks down or anything, and aside from the occasional stumble/hesitation, the car generally runs great.


I'm leaning toward IAC or MAP sensor at this point, I've ruled out the MAF sensor by unplugging it and trying to start the car. Got the requisite CEL, but still hard to start. Also ruled out the Fuel Pressure Regulator, it tested fine when I was diagnosing the previous issues with the car. AIR/EGR deleted, no cats, BBK Shorty headers w/ Magnaflow "cat-back". Just looking for any other possible avenues to check out. Car hesitates/bogs down randomly, it's not common, I may notice it once every two or three times I drive the car, usually under hard acceleration.

Going to replace the headers with long tubes/ORY, install an electric cutout, and swap in my SLP 2OTL exhaust next week, and I'd like to solve this issue while I'm wrenching.

[JCzNova]

Long Crank / Hard Start is normally a Viagra problem...


MAP, dirty/bad IAC ?

[popo8]

Are u inserting the key and going from off to start/run in one motion?.

I key on...let pump prime...the crank and i get instant fire. Not saying thats ur issue...but knowing ur technique may helpm

Co-Owner/Admin @ LTXtech.com

[93formulalt1]

Long Crank / Hard Start is normally a Viagra problem...


MAP, dirty/bad IAC ?

Lol I was thinking the same thing. Just hard to believe that it would fire right up before, and now that the car is running right, it takes forever to start. You don't think I got a bad Opti again, do you?

[93formulalt1]

Are u inserting the key and going from off to start/run in one motion?.

I key on...let pump prime...the crank and i get instant fire. Not saying thats ur issue...but knowing ur technique may helpm

Co-Owner/Admin @ LTXtech.com
Negative, I turn key to "On", wait for pump relay to cut off (after 2 second prime), then try to start. I've ruled out fuel issues, I've cycled the pump 4-6 times before attempting to start, and still takes forever to fire. I'm just hoping I didn't get another shit Opti, I'm going to be pretty pissed if I have to go through that mess again. Heck, had the car been running right before I replaced the timing chain, I would have done a cam swap at the same time. . . I want this thing to be running PERFECT before I start throwing go-fast goodies at it.

[JCzNova]

Lol I was thinking the same thing. Just hard to believe that it would fire right up before, and now that the car is running right, it takes forever to start. You don't think I got a bad Opti again, do you?

If it is running down the road after getting it started, I doubt it. No SES light? Just reading another updated thread on O2 sensors, don't think that is your problem but wanted to bring up the SES part.

[93formulalt1]

If it is running down the road after getting it started, I doubt it. No SES light? Just reading another updated thread on O2 sensors, don't think that is your problem but wanted to bring up the SES part.
No CEL on, only light I'm seeing is the occasional "Low Oil" light (bad oil level sensor) and ABS INOP light (still working on that one, I'd like to have my Cruise Control working again.) Used to have a Low Coolant light, but replaced the coolant level sensor, and haven't had any issues since.

Seems like the hesitation has been becoming more common lately, right after I made the repairs, it ran like new, but now, when trying to "have a little fun" on the highway, goosing the throttle on surface streets, etc., it just seems to be low on power. Could this be caused by clogged IAC passages in the intake? It was running on maybe 5-6 cylinders before I made the repairs, it ran REALLY bad for several months. Haven't done anything to it lately, just driving it. Had to order a pair of tires, since one of my rear tires developed a slow leak. Aside from that, I've been running only 93 octane fuel through it, not really beating on it too hard (because of the bad tires), and sticking mostly to driving on surface streets under 40mph.

[93formulalt1]

The car has 162k miles on it, any chance this could be due to stock fuel injectors on the way out? I was thinking of putting on the 22# injectors from my '93 on the '94, sending the '94 24# injectors in to be rebuilt and flow matched. It does seem to idle a little less smoothly than my '93 did when I had it running properly.

[93formulalt1]

nothing? i was considering swapping in my spare injectors, and sending the stockers to be rebuilt and flow matched. is it worth it? would it serve any benefit at all?

[JCzNova]

nothing? i was considering swapping in my spare injectors, and sending the stockers to be rebuilt and flow matched. is it worth it? would it serve any benefit at all?

It runs fine at higher RPM down the road? I wouldn't start at injectors, but guess that may be an issue. Not as likely as quite a few other things.

Someone else will hopefully chime in, but I don't see a benefit to flow matching injectors on a stock bolt-on car. Then again I have never done it to anything, and don;t know what that is costing you.

I would definitely check out the IAC, and if you can pull codes, you may have one "pending" and not popping the light.

[93formulalt1]

It runs fine at higher RPM down the road? I wouldn't start at injectors, but guess that may be an issue. Not as likely as quite a few other things.

Someone else will hopefully chime in, but I don't see a benefit to flow matching injectors on a stock bolt-on car. Then again I have never done it to anything, and don;t know what that is costing you.

I would definitely check out the IAC, and if you can pull codes, you may have one "pending" and not popping the light.
I don't have my scan tool here with me, all of my tools are back home, I'm working across the state, so I won't have access to that until Tuesday evening. Definitely going to be the first thing I check though.

Would the IAC cause the hard starting issue though? Seems like it could be the cause of the high idle, but the hard starting seems like it would either be fuel or spark related. When I started it today, it took about 4-6 seconds to start. It used to fire right up, even after all the repairs were made.

Also want to mention, I mentioned that the EGR was deleted, I was incorrect. The EGR is still in place, it was the secondary air injection that was eliminated. However, the EGR will be removed this week, as the long tube headers do not have provisions for EGR/AIR. I'll be installing the block-off plates, and possibly removing the intake to do some paint work on it, but I haven't decided yet. Either way, EGR will be gone at some point this week.

[93formulalt1]

Well, it seems that I'm having a fuel issue. . . Only parts in the fuel system that haven't yet been replaced are the Fuel Pressure Regulator and Fuel Injectors. Given the fact that if I cycle the pump 5-6 times, I can cut the crank time in half, I'm inclined to believe that one of these is the cause of my headache.

Tomorrow (well, today, as it seems), I'm going to have O'Reilly's order a new fuel pump in, and I'm going to rent a fuel pressure test kit to check the pressure at the rail again. If the new pump doesn't solve the slow crank issue and stumble/hesitation on takeoff, I will swap out the fuel pressure regulator. By logical reasoning, if the problem still isn't solved after that, it's likely a blockage in the line somewhere, a leak, or it's not fuel related at all. I believe it's fuel related, as the slow starting and hesitation are growing worse at the same rate, and aside from an IAC issue, the only causes of a slow start that I know of are fuel related.

I'll let you all know what I come up with, I should have the car fixed again in a couple days.

[audiorailroad]

change the fuel filter I have an old Sonoma that did that changed the filter and problem solved. and its cheap.

[Chrizar]

I'll be following this as I'm starting to have this issue with my car now, long cranks but when it fires it's fine. I've noticed throttle response going down the past few times I drove it as well. It did sit for over a year with a full tank of 93/110 leaded race gas mix..

[JCzNova]

Another quick thought while I'm online. Have you added fuel? Came across a vehicle a few years ago that would get an exact number of miles out of a tank then have fuel issues. Ending up being a pin hole in the intake pickup tube. As soon as the fuel got to that level.

I need to read your newer posts still tonight as well.

[93formulalt1]

Another quick thought while I'm online. Have you added fuel? Came across a vehicle a few years ago that would get an exact number of miles out of a tank then have fuel issues. Ending up being a pin hole in the intake pickup tube. As soon as the fuel got to that level.

I need to read your newer posts still tonight as well.
Filled the tank yesterday with 93 Octane, and a bottle of Techron fuel system cleaner. Car is still running worse, as in the hesitation/stumble is more prominent than it was. . .

Got a fuel pressure test kit, about to go check pressure at the rail.


change the fuel filter I have an old Sonoma that did that changed the filter and problem solved. and its cheap.
Fuel Filter was replaced at the same time as the pump, about 600 miles ago.

[popo8]

Filled the tank yesterday with 93 Octane, and a bottle of Techron fuel system cleaner. Car is still running worse, as in the hesitation/stumble is more prominent than it was. . .

Got a fuel pressure test kit, about to go check pressure at the rail.


Keep us updated...

[93formulalt1]

Tested the fuel pressure at the rail, car seems to be priming to about 50-60PSI, then rapidly bleeding off. At idle, the car sits at 50PSI. As soon as the car is shut off, pressure bleeds off to nothing almost instantly.

Funny thing is, it almost seems as though the fuel system develops a vacuum right after engine shut off, as I tried to release pressure from the pressure gauge, it started sucking the fuel out of the drain hose back into the engine. . .

I'm leaning toward a leaking injector, as I started the car with the fuel pressure regulator disconnected, and pressure did rise to about 60PSI at idle, but what could cause the "vacuum" at idle? Is that a problem with the pump itself? I'm at a loss at the moment, and tempted to take it to a shop to have it diagnosed, then make the repairs. . .

[popo8]

Idk about the vac...but ur psi is way higher than called for.

Co-Owner/Admin @ LTXtech.com

[93formulalt1]

Idk about the vac...but ur psi is way higher than called for.

Co-Owner/Admin @ LTXtech.com
I'm going to attempt to get my hands on a better gauge tomorrow, the one I rented from Autozone was a total POS, and the values would change drastically just by moving the gauge around a little bit.

I'm not so sure about the pressure reading, but the fact that it's sucking fuel back in through the schrader valve is a concern, and the fact that as soon as the system primes, the pressure bleeds off immediately leads me to believe I'm on the right track.

Where are we leaning? FPR? Injector issues? I have a parts car, tell me what to swap, and I'll swap it! haha

[Soxxpuppet]

If you disconnect the vacuum hose that goes from the regulator to the intake, do you smell fuel in it? If so you might have a bad FPR. Overly high fuel pressure might be causing some sort of problem with the starts aswell. A good way to check injectors is to pull the rail off the intake. Keep the injectors in the rail and have someone prime the fuel pump while you check the injectors to see if there leaking.

[93formulalt1]

No smell of fuel in the vacuum hose, no fuel leakage from the FPR, and disconnecting it while running the car instantly impacts fuel pressure, so I'm led to believe the FPR is working properly. I'm still trying to figure out if the fuel pressure test kit I had was as shot as I think it was... I don't know why I have so much trouble with those things, but I'm considering a permanent mounted one on the schrader valve to avoid the headache that comes with trying to find a working fuel pressure gauge every other week.

I'll see if I can get another one, just to be sure, as the gauge itself may have been leaking. I'm suspecting the ICM may be the culprit also, as I've heard that can cause hard start and hesitation issues when it starts to go kaput. I don't think I have another spare ICM laying around, however, and I haven't had the money to replace it. I do know, know that I'm thinking about it, that it isn't spaced off the block, so it may be starting to show signs of heat damage.

[93formulalt1]

I swapped a spare ICM onto the car, didn't seem to make much difference. Swapped an old coil onto the car, and it started right up, but the hesitation was still there. . .

Took it for a ride, it is almost as if the car is turbocharged, and it suffers from severe lag until exactly 2000 rpm's. . . If I take off slowly, and stomp the gas below 2000 rpms, it won't go, it only accelerates slightly faster, then it's like a switch is flipped, and it runs like a banshee above 2k. I'm completely stumped. I did find a spare throttle body from a '96, with the TPS, IAC, and all other hardware still intact, so I'll go ahead and swap the IAC and TPS, to see if that may help. . . Going to space the ICM/Coil assembly from the block about 1/2", to cut down on heat soak.

Car is running close to 200* under normal operation, will pass the 210* marker on the temp gauge if I get stuck in traffic. Seems a little high to me. . . Fans are kicking on around 195. Checked coolant level, it's right where it should be.

[Soxxpuppet]

ats around normal operating temp for the coolant. It sounds like it may be a tune related issue. Did you tune the car anywhere inbetween? Clogged cat bad 02's?

[93formulalt1]

Cleaned the TB today, replaced the TPS and IAC, no change. I'm at a loss. I seem to remember a slight hesitation in my '93 after installing long tubes and CAI, seemed to disappear after I had it tuned. . . Maybe that's the problem? It's got full exhaust and a CAI right now, the CAI is a cheaper unit, but I should be picking up an SLP CAI in the next few weeks.

Is it possible that it's because of the lack of tuning after the headers/CAI that is causing the low RPM hesitation? That wouldn't explain the hard start, but I'm just tossing ideas out there. I'm going to have O'Reilly order another fuel pump, and I'll swap that out this weekend, and see if it helps, but at this point, I'm not sure what could be causing the issues I'm dealing with.

[Chris]

What are your fuel trims? Disconnect the battery for ten minutes press the brake reconnect see if it fires right up. Lead toward tired o2s or an vaccum leak biasing your trims.

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[Chris]

Fwiw ac delcos 02 > bosch

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[93formulalt1]

ats around normal operating temp for the coolant. It sounds like it may be a tune related issue. Did you tune the car anywhere inbetween? Clogged cat bad 02's?

Car hasn't been tuned while I've owned it, I've been trying to get it running right and finish a couple other mods before I spend the money on a tune. No cats, O2's were replaced 3-4 weeks ago.


What are your fuel trims? Disconnect the battery for ten minutes press the brake reconnect see if it fires right up. Lead toward tired o2s or an vaccum leak biasing your trims.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

I thought the same thing, but checking the O2 values while car is running, they are functioning properly. I'm leaning toward a bad fuel pump check valve at this point, given the fast bleed-off of fuel pressure after priming. I read some reviews on the brand of fuel pump I used, and at this point, I'm more than willing to blame a crappy part for my issues. I'll get another pump from them under warranty, and if I have any further problems, I'll be getting my money back and ordering an AC Delco part. Or going with a Walbro or other quality aftermarket pump.

Don't get me wrong, the car is running great, it's a minor hesitation at low RPM's, that seems to clear up around 2k RPM, and the car has PLENTY of power after that. It's still drivable, gets decent mileage, and has enough power to get into trouble, it's just this minor issue that is keeping the engine from running at 100%, which has been my goal since I bought the car.


I have tried a few things already this week, then last night, got frustrated, and decided to wash/wax the car. What a mistake. . . Found a couple of spots where rust is starting to form under the paint that went previously unnoticed. . . Now I'm looking at my options. Can't afford a repaint at this point, really don't want to drive around in a car with primer spots. Why can't this just be easy?


I guess I'll start saving my pennies to buy the materials for a paint job and some body repairs. Should be able to get it where I want it, appearance-wise, for about $2k in parts and materials. I want to paint the rims, ram-air hood, high-rise hatch with custom spoiler, new taillights with light tint, LED corners with same light tint, and some custom graphics for the tail panel, "Formula" logos, and a couple other little things). The sooner I get the mechanicals straightened out, the sooner I can start accumulating parts to get started on the body repairs, panel fitting, and paint work.

[93formulalt1]

SONOFA*****!!!!!!


Just got a CEL, scanned it, I've got a Low Res Pulse code again. . . . . . . . . In addition to a MAF code (undoubtedly from when I unhooked the MAF to see if that's what was causing my issues) and an EGR code. EGR valve could cause the low RPM hesitation, but I wouldn't think it would cause hard starting issues. Honestly, at $60+ for a replacement EGR valve, it's going to have to wait. I'm beyond broke right now, I've been waiting over 2 weeks for my $550 security deposit from my last apartment, and the landlord is dragging her feet getting it paid back. I loaned Mom some money so she could be with my sister for the birth of my niece a few weeks ago, which was over $600 that I really couldn't spare at the time, but made it work. . .



I'm about done with this Opti BS. I'm broke, can't keep the ******* thing on the road for more than a couple weeks at a time before another one of the brand new parts I bought fails again. . . I'm relying on this car to keep me mobile through the summer, and now I have a brand new opti, with less than 1000 miles on it, that's on borrowed time again. . . I can pull it, replace it under warranty (wait a couple days for the new one to arrive, of course), and hope this one works, but this is the 2nd failed Opti by this manufacturer, and honestly, I'm getting tired of replacing Optis.




I'm seriously considering trading this POS for the LS1 car that my buddy offered me. . . It's not the car I want, it's in need of LOTS of work, but it would be a far cry more reliable than the POS I'm trying to drive now.



I'm walking away for a little while, if I keep stressing over it, I'm going to have a ******* aneurysm.


Sorry for all of the implied swearing, but I'm beyond angry right now, I'm about ready to throw in the towel, sell the Formula, pay off my Malibu, then sell that and buy an LS1 car. I'm trying my hardest to stick with the LT1, but this finicky ***** is REALLY making it difficult to not want to jump ship.

[firebird_1995]

Sorry to hear that. Unfortunately this is what happens with most guys. They get an lt car, throw a bunch of money and parts at it, then get pissed and sell it. Proper diagnostics and testing go a long way. Have you inspected the wiring harness for brittle or broken wires?

[93formulalt1]

Sorry to hear that. Unfortunately this is what happens with most guys. They get an lt car, throw a bunch of money and parts at it, then get pissed and sell it. Proper diagnostics and testing go a long way. Have you inspected the wiring harness for brittle or broken wires?
I have. I should also mention, the Low Res Pulse code has NOT hindered the car's operation at all. Seems to throw the code after some "spirited" driving, but the car does not die, always starts up fine, and never exhibits any other symptoms than those described earlier in this thread. I'm willing to bet it's a random, intermittent code, as it's not causing failure above the issues already mentioned.

Opti harness was replaced when I put the last brand-new Opti in about 4 weeks ago, and again the time before that, about 6-8 weeks ago. And the time before that, about 10-12 weeks ago. And the time before that, about 9 months ago. I've inspected all wires under the hood, the only damaged wires were those on the O2 sensors, which were on the sensor side, and have since been replaced. Inspected connections to PCM while I was doing the CAGS/Skip Shift disable by removing the CAGS solenoid and dash light wires from the harness. All wires are in good condition, with solid connections.



Another thing I should mention, this is NOT the first LT1 car I've owned. I know how wonderful these cars are when they are running properly, but I just can't seem to get this one to the same level as my last 3 LT1 cars. My first car was a '95 LT1 B-Body, I've had '93 and '95 LT1 F-Bodies as well, all of which ran perfectly with routine maintenance, the '95 had 115k on it when I sold it, the B-Body had 195k on it, and the '93 has 170k on it currently. Seems like the '94 I'm fussing with just seems to have been poorly maintained throughout it's life, and my pockets are just too shallow to make up for a lifetime of neglect. Sad thing is, I'm in too deep to call it quits, and the car really is in great shape, given it's age and mileage, and I would love to keep it and make things right mechanically.

I just don't know what to do at this point. Frustration is setting in, and I'm concerned that the car is going to leave me stranded some point in the near future.

[93formulalt1]

Hard Start tracked to an intermittent Low Res Pulse circuit malfunction. Checked connections, looks alright, I'm not seeing any damaged wires, I'm completely lost. DTC 16 is thrown at startup. Any ideas where to look next? I checked the upper connection to the engine harness at the opti harness, all appears to be fine. Car is triggering a DTC 16 at startup, which resolves quickly and car will eventually start up fine.

I'm leaning toward a bad optical sensor in the Optispark. . . Didn't have this issue with previous Opti, it's only since I replaced it that I've got a hard start issue. Harness was replaced, no issues out of last 3 Opti's, it's just this one that has given me an intermittent DTC 16. I'm planning on replacing it (AGAIN!) next time I'm home, under warranty. I'm hoping I have my other 2 new tires by then, and I'll be ordering a new clutch in the next couple months also.

[Chris]

Off the wall idea. If its only set at start up, voltage drop the circuitry to the opti. I wonder if poor voltage is inducing it. Once it fires bat voltage is raised and your good.

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[Soxxpuppet]

Off the wall idea. If its only set at start up, voltage drop the circuitry to the opti. I wonder if poor voltage is inducing it. Once it fires bat voltage is raised and your good.

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Ya know what. Thats not that bad of an idea. The opti works on a very finicky voltage. Any higher/lower itll cause issues. My friends supercharged mustang idles like Crap.. Until you give it some revs or drive it. turns out the alternator at low rpm isnt putting out proper voltage.

[93formulalt1]

Off the wall idea. If its only set at start up, voltage drop the circuitry to the opti. I wonder if poor voltage is inducing it. Once it fires bat voltage is raised and your good.

Sent from my SAMSUNG-SGH-I497 using Tapatalk 2


Ya know what. Thats not that bad of an idea. The opti works on a very finicky voltage. Any higher/lower itll cause issues. My friends supercharged mustang idles like Crap.. Until you give it some revs or drive it. turns out the alternator at low rpm isnt putting out proper voltage.

Battery was put on the charger today, and the car still cranked hard. I had the same idea earlier, thinking that the constant hard starting issue may have caused battery drain, but with the battery fully charged, the problem persisted. Any chance it may be an issue with the PCM? I thought that a PCM issue would have led to a DTC 16 AND a DTC 41 or 42. . .

I'm at a loss. Seems that power is slightly restored at low RPM after fuel pump replacement, although it still seems to be unable to accelerate as smoothly as it should in 6th gear at highway speeds. If there's anything else I should be looking at, or tests I can perform to verify it's an internal Opti issue, as I'm leaning toward an optical sensor failure at this point. Had O'Reilly order me a new Opti today, it'll be in tomorrow morning, and I'm planning to replace it Monday. Problems started with the most recent opti, it's been starting hard since I installed it, so I'm willing to lay blame on the Opti at this point.

[93formulalt1]

Just to verify it wasn't a bad opti harness, I swapped it out with a spare I had laying around before I pulled the opti. Still starting hard. Pulled the opti, got the new one, just finished putting loctite on the rotor screws, sealed the opti with RTV, just waiting for it to cure before I install the new opti and test fire it. Hopefully it'll fire right up, I'm pretty confident this is going to fix it.

[93formulalt1]

Just started it. . . Still starting hard, still throwing a Low Res Pulse code. When I come home in a few days, I'll re-run the low-res pulse wire from the opti harness connector to the PCM and see if it continues. If it does, I'm leaning toward a PCM issue. If that fixes it, I'll re-pin the PCM harness and Opti Harness, run the new wire inside the factory looms, and let it be.

[93formulalt1]

Since I seem to be just talking to myself in here, I guess I'll throw out the idea I had. . .

Is it possible that the problem lies in another part of the ignition system? Or does the DTC 16 kind of limit the possibilities to wiring, Opti, and PCM? For example, could a bad ICM cause that code to pop up?

[firebird_1995]

You're not talking to yourself. I check this thread every time something is posted. These problems are frustrating all around.

So I'll throw some things out also....
Pcm failure is rare, but it happens. Have you done the shbox method for checking the opti? There are a few voltages that can be tested that come from the pcm that may help diagnosing a bad computer. And I'll say it again, a datalog would be nice to see. Although it may not show us anything, the fact that your issue pops up after "spirited driving" gives us a chance to compare logs between that and normal driving for irregularities.

Also
I just looked through my service manual for DTC 16. One thing that caught my eye is it states a DTC 16 will set intermittently if the high and low resolution signals are shorted to each other. I think your idea about running a new low res wire from the opti harness connector to the ecm is a good idea. Do eet.

[93formulalt1]

You're not talking to yourself. I check this thread every time something is posted. These problems are frustrating all around.

So I'll throw some things out also....
Pcm failure is rare, but it happens. Have you done the shbox method for checking the opti? There are a few voltages that can be tested that come from the pcm that may help diagnosing a bad computer. And I'll say it again, a datalog would be nice to see. Although it may not show us anything, the fact that your issue pops up after "spirited driving" gives us a chance to compare logs between that and normal driving for irregularities.

Also
I just looked through my service manual for DTC 16. One thing that caught my eye is it states a DTC 16 will set intermittently if the high and low resolution signals are shorted to each other. I think your idea about running a new low res wire from the opti harness connector to the ecm is a good idea. Do eet.


I plan on buying a cable so I can datalog at some point in the next couple paychecks (negotiating a pay raise and better benefits with my boss now, should have more expendable income in a couple weeks).

I don't know if the two are connected (DTC 16/hesitation off idle-2k RPM), but I know the DTC 16 is setting while engine is cranking, which is causing the hard start condition. The fact that the low RPM hesitation doesn't resolve when the code is clear, I'm guessing that's a secondary problem that will require some attention. I'll look into this stuff further when I return home on Thursday, I'm just relaxing a bit before I drive back across the state tonight. Maybe it would be a good idea to pull the tape and wire looms off the factory harness to see if maybe there is some damage to the wires in there? Hard to tell though, as a broken wire inside the insulation could cause the same symptoms as shorting out, as would a loose/poor connection somewhere along the route the wires take.

[Chris]

If you voltage drop the circuits you dont have to cut the loom. Disconnect the pcm and opti supply 12v on the pcm side and ground a light bulb out optI side. Take a multimeter and place it at the red at the pcm connector and black athe opti. You shouldn't drop more than 0.3v

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[JCzNova]

If you voltage drop the circuits you dont have to cut the loom. Disconnect the pcm and opti supply 12v on the pcm side and ground a light bulb out optI side. Take a multimeter and place it at the red at the pcm connector and black athe opti. You shouldn't drop more than 0.3v

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

I would continuity check as well, see what kind of resistance that wire has unplugged at both ends.

[93formulalt1]

Well, I found a new symptom... The DTC 16 is NOT set only when starting or after spirited driving, last night, I was able to confirm that the code sets every time I turn on the ignition, before attempting to start. Clear the code, turn off ignition, turn back on, code is back. Seems like its a PCM issue, doesn't it?

[JCzNova]

Well, I found a new symptom... The DTC 16 is NOT set only when starting or after spirited driving, last night, I was able to confirm that the code sets every time I turn on the ignition, before attempting to start. Clear the code, turn off ignition, turn back on, code is back. Seems like its a PCM issue, doesn't it?

System Voltage too low.... Hmm, are you in a garage or close enough to a plug in where you can have a charger on the battery while doing this process?

I popped that code over the winter, and I ended up not having a good connection on the connector on top of my alternator, so it was intermittently exciting and charging, while draining the battery while driving to and from. Doesn't sound like your issue at all, but I will check all kinds of stuff before starting to throw parts at it.... Anybody near you that has an LT1 also, that you could throw their ECM in and test again?

***Edit***
Just thought some more, have you tried pulling fuses to other stuff? i.e. If you have something that is ignition only power and for some reason has a huge enough draw to pop that code on you? If that sounds crazy, please somebody stop me. :D

[93formulalt1]

System Voltage too low.... Hmm, are you in a garage or close enough to a plug in where you can have a charger on the battery while doing this process?

I popped that code over the winter, and I ended up not having a good connection on the connector on top of my alternator, so it was intermittently exciting and charging, while draining the battery while driving to and from. Doesn't sound like your issue at all, but I will check all kinds of stuff before starting to throw parts at it.... Anybody near you that has an LT1 also, that you could throw their ECM in and test again?

***Edit***
Just thought some more, have you tried pulling fuses to other stuff? i.e. If you have something that is ignition only power and for some reason has a huge enough draw to pop that code on you? If that sounds crazy, please somebody stop me. :D
You know, come to think of it, a buddy I had helping me right before this all started did have the alternator out so we could get at the header on the pass. side a little easier. . . Possibly not hooked back up right? Loose connection? Battery is brand new as of 4 months ago, seems to be running a little lower than I'd like. I did hook it up to the charger last Thursday, didn't seem to help at all, but I only had it on there for about 3 hours or so.

I'll check the alternator connections on Thursday or Friday when I get home, as well as visually inspect all of the engine grounds and battery cables.

Aside from a voltage issue, what could cause this issue?

[93formulalt1]

Does anyone know if the factory coil wiring must be modified to run an MSD "Blaster" coil? I only seem to remember 2 wires being grounded, but a friend with a '96 has 3 in the factory harness that are grounded at the ICM stud. . . Just wondering if '94 was the same as the later models, or if the wiring was modified to make the MSD coil function. . .

[Chris]

There are two diffeeent styles of coils used on the lt1 cars. That being said there is no real reason to go to the msd coil unless you are running a very large compression numbers.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

[93formulalt1]

There are two diffeeent styles of coils used on the lt1 cars. That being said there is no real reason to go to the msd coil unless you are running a very large compression numbers.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2
No, the car HAD an MSD "Blaster" coil on it when I bought it, I was just wondering if the PO may have hacked apart the stock wiring to make it work, maybe there is something he did that is causing my issues now, since I swapped the MSD out for a factory replacement coil.

[93formulalt1]

Alright, I'm still at a loss. Pulled the battery ground on pass. wheelwell, cleaned all connectors, bolt, and cleaned the wheelwell with some degreaser, just for the heck of it. Also pulled the connector on the ICM and found that it was missing the little rubber insulator thing, so I pulled the one off the same connector on the parts car, put it on, and cleaned the ground wires on the ICM/Coil stud. There was a bad looking ground wire there, so a buddy of mine cut off the hacked-together ground, soldered a 2-3" piece of 14-16ga wire to it, soldered an O-terminal on, and heat-shrink and electrical taped it up. . . Connections looked good, but that was the only wiring thing we did to the ignition system while we did all the work to it when this issue started. . . Just wondering if maybe that wire is insufficient as a ground, and maybe I should extend each wire individually, with their own o-terminals to ground them?

Also, I haven't had a chance to check fuses yet, but could a blown ignition fuse cause a DTC 16?

[93formulalt1]

New symptom: With air filter removed, if I don't let the pump prime (turn key all the way to "start" without pausing at "run"), car starts right up. Air filter on, car takes longer to start. Replaced air filter with a larger K&N filter, issue persists.

I'm losing my mind. I contacted the guy who wrote the "How the Optispark Works" article stickied in this section on Facebook to get his thoughts, waiting for a response at this point. Maybe he'll have some insight.

[firebird_1995]

Have you done the voltage test on the circuits from the pcm to opti?

[93formulalt1]

Have you done the voltage test on the circuits from the pcm to opti?
Haven't had a chance, I can't find my multimeter. I'm looking for it, though. Worst part of it all, I have to head back across the state tomorrow, where I work, and since one of the other guys just quit, I'm working 72 hour weeks until we replace him.

Also, the new tires I just ordered (Falken 512's) have been backordered, so I cancelled the order, am returning the 2 tires I already have, and I'm going with Kumho Ecsta 4X KU22's in 275/40ZR17. Almost went with Nitto NT555's, but I don't race, or plan to keep the 17's on the car if I do, so I would just be shooting myself in the foot with worse tread life.


EDIT: I decided, since the distributor isn't actually turning at all with the engine off, it would be a good test to just plug in the spare Opti I have laying around, just to see if the code is still showing at key on/engine off. . . Well, no codes at key on with the old Delco opti plugged in. Dammit.


Anybody have any idea where I can find a decent deal on a Delco/Delphi opti? Can't really spend $500 on a distributor, just dropped $620 on tires. Willing to buy a low mileage used one, as long as it's known to work.

[93formulalt1]

Since I know enough about the way the Opti system works, I think the fact that the last 2 Optis were bad out of the box (they work, but throw DTC 16 out of the box), I'm going to try ONE MORE TIME. I'll have the parts store order 2 new Opti's, and test them in the parking lot by just connecting the harness/opti to the ignition harness in the car. If it throws a DTC 16, no go, send it back. If it works, I'll give it a shot, and install it. If I have any trouble after that, I'm probably going to flip my lid, remove it, and swap the 170k Delco opti from my parts car in, since I know that one works. . .

[93formulalt1]

Just checked voltage at ignition test connector- 5.2, 5.2, 12.4, and Ground. Did same at opti connector, same voltages, no noticeable voltage drop across any of the wires.

I did notice that with the engine off, the PCM is detecting that the engine is turning at 45 RPM's. I've been told that a poor connection to ground can cause the issue I'm having, I found a Corvette owner who had the EXACT same issue, he said he tracked it to a bad ground. I'm going to pull apart the repaired ground that my buddy did a few weeks ago, and re-do it myself, just to be sure. I'm not doubting his work, I'm just thinking that the wires he worked with were the ONLY wires we touched at all between the last time the car started as it should, and when the issue started.

Hopefully that will repair the issue, if it doesn't, I think I'm going to rip out what hair I have left. Heck, if it does fix the issue, I'm probably still going to rip out my hair. haha

[JCzNova]

Since I know enough about the way the Opti system works, I think the fact that the last 2 Optis were bad out of the box (they work, but throw DTC 16 out of the box), I'm going to try ONE MORE TIME. I'll have the parts store order 2 new Opti's, and test them in the parking lot by just connecting the harness/opti to the ignition harness in the car. If it throws a DTC 16, no go, send it back. If it works, I'll give it a shot, and install it. If I have any trouble after that, I'm probably going to flip my lid, remove it, and swap the 170k Delco opti from my parts car in, since I know that one works. . .

Be careful testing in the parking lot. A lot of places will not return electronic parts once they have even just been plugged into a vehicle.

[93formulalt1]

Be careful testing in the parking lot. A lot of places will not return electronic parts once they have even just been plugged into a vehicle.
I'm friends with just about everybody at the local place I have been getting these things.

I cleaned all of the engine grounds last night, replaced the ground wires for the ignition at the driver's side head, and voltage tested the Opti harness. All wires tested as they should. Like I said above, plugging in my old Delco opti eliminated the DTC 16 at key on, so I'm fairly confident the problem lies in the opti itself. Like I said, I'm going to give them one more chance to get me a working part, and if that doesn't work, I'll pull the Opti off my parts car, swap it, return the aftermarket one, get my money back, and buy an MSD or Delco when I find a deal, just to have on hand when the one from my parts car fails.

[JCzNova]

I'm friends with just about everybody at the local place I have been getting these things.

I cleaned all of the engine grounds last night, replaced the ground wires for the ignition at the driver's side head, and voltage tested the Opti harness. All wires tested as they should. Like I said above, plugging in my old Delco opti eliminated the DTC 16 at key on, so I'm fairly confident the problem lies in the opti itself. Like I said, I'm going to give them one more chance to get me a working part, and if that doesn't work, I'll pull the Opti off my parts car, swap it, return the aftermarket one, get my money back, and buy an MSD or Delco when I find a deal, just to have on hand when the one from my parts car fails.

Let us know if that ends up being the fix. The wife got a V6 and it popped the low voltage code on the way home last night. Found when the PO had the battery replaced in November at Walmart, someone stripped out the positive terminal threads on the battery and it will not tighten past finger tight.

[superspirit]

wow 6 pages and no ending

[Flyinz]

Any update for this?