LT-1 Swapped S-10 shuts off at WOT

[JKPhillips]

I have a question. I have a LT-1 swapped S-10 (motor is from a 96 SS Z-28) and I changed the header gaskets, installed 2 new O2 sensors (4 wire) temp sensor in the water pump and 2 spark plugs that were bad and when you drive down the road its fine but, when your at WOT it will take off for about 3-4 seconds and completely shut off and with the throttle still WO about 3 seconds of being dead lol it will take back off WO and just keep doing this. What could this be? Other spark plugs maybe? Fuel Pressure regulator? TPS?:cry:old pic 25885

[Ugod02010]

If u take the vacuum line off the regulator it simulates full throttle. Hook up a pressure tester, unhook and plug vacuum line and see what ur fuel pressure is. Also if possible mount ur pressure gauge somewhere u can see it while driving and go WOT pressure should stay around 45-47

[popo8]

I know our members will be able to help u. Im looking fwd to seeing more about ur truck. Would u mind startin am intro thread with more pics amd info. It looks really nice.

LTXtech.com is my drug.

[popo8]

@tubbyz is this what u experienced?

LTXtech.com is my drug.

[Fastbird]

I'd look for electrical wires being tight enough to be pulled when the motor torques and moves while you go to WOT.

[firebird_1995]

What are you running for a fuel pump and tank? Is the tank baffled?

[JKPhillips]

It has a new fuel tank, sender and 340lph fuel pump. The s-10 came out fuel injected so I just switched in a bigger pump and all the wiring has enough slack I built the wiring harness and deleted everything not needed. Its the 4th one I have swapped and built but i'll check again. Couldn't check pressure today because it 32 out and I dont have a garage. I will double check wiring, tank and pump, pressure and install new plugs tomorrow. Thanks for the replies.

[JCzNova]

One more log on the fire. Verifying the TPS is operating correctly. Maybe at the top end it is going crazy on resistance. My just went out on the low end, and I replaced the sensor and connector.

Let us know what you find.

[JKPhillips]

I ordered a new one yesterday lol will be installing when it comes in. I'm trying to cover all bases. Thanks for the info though.

[JKPhillips]

Ok so the fuel pressure is 42-43psi at idle and when you unplug it it goes to 50psi. Plug it back in 42-43psi. WHEN YOU REV THE ENGINE IT JUMPS FROM AROUND 38-45PSI. Unplugged the temp sensor and it got worse but, still having the same problem. What about knock sensor or maybe I got a bad temp sensor at Autozone? Any ideas?

[blkchevyz]

does it actually shut off or is it just cutting out really bad?
is it a specific rpm where it happens?

[JCzNova]

If you unplug the coolant temp sensor, jump the wires with a paperclip. It will be reading very hot then. Mine was reading -65 degrees or something like that and dumped a bunch of fuel in, ten if I punched it there was a stumble or even shutoff. If I eased into it I could climb the rpm range.

[Ugod02010]

Fuel pressure is pretty much dead on. It is possible u got a crappy temp sensor. But if it seems to get worse when unplugging i would set that idea aside for the moment. Do u have acess to a scanner or where u can get live engine data? Or at least check for codes?

[JKPhillips]

It doesn't have the scanner port anymore guys I built the harness. It seems to die around the same spot on the throttle and from that point on. No matter if you gas it all at once or steadily give the GO. If you hold it WO it will run for 2 sec then shut down like you turned off the key on a stick shift then it will take back off again for about 3 sec and do it again and again and again and again. It does pop once or twice but not bad just like it loading up a little. Only pops when it takes back off again. I have a 93 TPS on the throttle body but the harness and throttle body is a 96? I know 93 is adjustable and the 96 is not but, do they operate on the same volt level? Also ima check my coil tomorrow seems like on a Corvette form a guy had a coil not strong enough at WOT to burn all the gas.

[JCzNova]

That sounds more like your "rev limiter" in the fuel cutoff tables if kills fuel at a certain rpm, the fuel back on at another rpm.

[popo8]

Without a port, how are you tuning the computer for anything, or is the motor stock that it requires no additional tuning.

[GuillaumeC]

You only need two wires to datalog or scan, a ground and the data wire. I suggest you get a ODB connector and wire it so it works. It can be temporary and just loose wires zip-tied and routed in the cabbin.
If you can't know for sure what's going on you'll be shooting in the dark.

It may be dumping fuel and cutting out, it may be leaning out really bad, it can also be ignition related, etc...

I've driving a car that had pretty much the same symptoms you're describing, it was an old cavalier with a clogged catalytic converter. Drove fine at low throttle but completely shut off and on while accelerating.

[JKPhillips]

I was thinking TPS? I have a new one on the way then i'll swap the coil with another one that I know works. I'm going to install a Scan port but usually a LT-1 will run with some bare essentials lol like the 93 models. Do they have a built in rev that I can have removed its doing it around 3500-4000 so its not triggering or I wouldn't think so.

[GuillaumeC]

Did you test the TPS before you ordered a new one?
All you have to do is measure the voltage @ the TPS input pin on the PCM while you do a sweep from no throttle to WOT. You can do it with key "ON" engine not running.
You want to see under 1V @ closed throttle and close to 5V @ WOT. Voltage should raise in a linear way from 1 to 5V with no "dips" in voltage.

You can also check it very easily with a scanner.

[GuillaumeC]

Also, did you try another coil wire? The one from the coil to the opti. My caprice once had a bad coil wire that caused a similar problem.

[JCzNova]

I was thinking TPS? I have a new one on the way then i'll swap the coil with another one that I know works. I'm going to install a Scan port but usually a LT-1 will run with some bare essentials lol like the 93 models. Do they have a built in rev that I can have removed its doing it around 3500-4000 so its not triggering or I wouldn't think so.

It wouldn't be that low unless someone set it that way. It is in the tune, so you could raise fuel cutoff to 8k rpm but there is no removing it.

[JKPhillips]

Ima test the TPS voltage and the coil tomorrow. The reason I didn't test it is because the harness PCM and throttle body are 96 SS Z-28 and the TPS I installed is a 93 Z-28 Speed density, they call for different part numbers and the way the PCM reads them is different. I might be wrong but, wasn't the 93 a ECM and the 96 a PCM?

[popo8]

... I might be wrong but, wasn't the 93 a ECM and the 96 a PCM?

You are correct.

[JCzNova]

Ima test the TPS voltage and the coil tomorrow. The reason I didn't test it is because the harness PCM and throttle body are 96 SS Z-28 and the TPS I installed is a 93 Z-28 Speed density, they call for different part numbers and the way the PCM reads them is different. I might be wrong but, wasn't the 93 a ECM and the 96 a PCM?

Yes 93 ECM and 96 PCM.

I can look up the resistance tables if you want to see if the sensors read the same, even though they are different part numbers.

[JKPhillips]

yeah that'd be great. Even if they are ima change to the 96 one like it calls for just to be on the safe side. 93 is adjustable and 96 I think I read the 96 PCM adjust it?

[JCzNova]

The 96 says .6V to WOT of 4+ Volts.

The 93 doesn't give me any of that on alldata, but those are the numbers my '93 just gave me.

[JKPhillips]

ok i'll keep you guys posted tomorrow.

[Ugod02010]

I had a honda that had a dead tps and it was pretty similar to what ur describing. Cutting out really bad under WOT or just hard acceleration. I'm also with whoever said about adding a scan port. U need 2 wires and any future trouble it will help big time!!

[beaver50]

Nice truck!!

[JKPhillips]

Ok so no work on the truck today but ima install the TPS when it comes in the mail and a new MSD coil and unhook my Tach and see what that does. Also ima hook up a OBD port its the Blue connector on the PCM. Pin 7 and Pin 30 hopefully I get it fixed before to long and I can use the Port for tuning lol







PCM Connector C4 (BLUE)


1
TAN/WHT
551
PCM Ground


2
LT BLU/WHT
1229
Transmission Pressure Control Sol Low


3
PNK
439
PCM Ignition Postive Voltage


4
not used




5
not used




6
BRN or LT GRN
418 or 1652
Transmission TCC PWM Sol Control (AUTO 1995+) or Reverse Inhibit Sol Control (Manual)


7
PPL
1807
Serial Data (Class 2) 1996+ (OBD2 Port Pin 2)


8
DK GRN/WHT
459
A/C Clutch Relay Control


9
BRN/WHT
419
MIL Control (PCM Supplies GROUND for light)


10
DK GRN/WHT
428
EVAP Canister Purge Sol Control


11
TAN/BLK
422
Transmission TCC Sol Control


12
RED/BLK
380
A/C Refrigerant Pressure Sensor Signal


13
not used




14
not used




15
WHT
375
Skip Shift Lamp Control (Manual)


16
PNK
1439
Change Oil Lamp Control (B-Body ONLY)


17
not used




18
not used




19
not used




20
WHT/BLK
448
Output/Field Service Enable (Diag Port)


21
LT BLU
1876
Knock Sensor Signal Left (1996+ B-Body ONLY)


22
DK BLU
496
Knock Sensor Signal F-Body, 1994-95 B-Body (1996+ Right B-Body)


23
not used




24
DK BLU
732
A/C Evaporator Temp Sensor Signal (F-Body ONLY)


25
not used




26
DK GRN/WHT
357
Engine Oil Temp Sensor Signal (Corvette)


27
not used




28
YEL/BLK
1227
Transmission Fluid Temp Sensor Signal


29
TAN
800
Serial Data (UART) (Some B-Body) (Diag Port)


30
TAN
800
Serial Data (UART) (Most F-Body & B-Body) (Diag Port)


31
not used




32
not used

[Ugod02010]

I know u want the tan wire I think u will need the white/black wire also tho. What ur is the engine/PCM?

[Ugod02010]

http://shbox.com/1/DLC_wiring.jpg

[JKPhillips]

Its a 96 thanks for that link thats awesome. I will use it when I go to install it.

[JKPhillips]

UPDATE! I checked the TPS and its .58v at idle and 4.50v WOT so its good. The FPR is staying open. When I turn the key on it runs fuel back to the tank continously. You can start the truck and unhook the FPR and it wont change but with it unhooked and idleing you can clamp the fuel line and it will load up. So the FPR is bad I will be changing it tomorrow and keep everyone updated. Unless anyone has one for a 93 I can have?

[SSlowBoat]

@tubbyz is this what u experienced?

LTXtech.com is my drug.


yeah the first time. now it does it EVERYWHERE. lite throttle hard throttle high rpm low rpm idling driving. idn what the hell it is yet. im down to fuel pump or opti. fuel pressure at idle is perfect with or without vacuum. im listening in here to see what he comes up with

[popo8]

Im gonna go with opti man...esp with ur previous code.

LTXtech.com is my drug.

[popo8]

vacum off pressure should rise. vac on...in the 43 range.

LTXtech.com is my drug.

[JCzNova]

Hate to be the bearer....

Opti.

[SSlowBoat]

after talking to a few more people i am going with opti for my case, your issue may very well be the regulator, but i dont think it is

[JKPhillips]

My pressure is fine also. 40psi key on, 43psi idle, 50psi unhook vacuum and 38psi to 45psi reving up. Mine runs fine everywhere I go until I start to call on it and around 4000rpm it shuts off then back on again. Like I stated earlier my FPR lets fuel right past it. I took the line off of it and fuel flows constantly with the vacuum on or off it dont change. B 4 all this my fuel pump would pressurize and prime up before starting now it don't. I have a GM opti if the FPR doesn't work though. THANKS guys you all are alot better than most sites I have been on about helping others.

[GuillaumeC]

my FPR lets fuel right past it. I took the line off of it and fuel flows constantly with the vacuum on or off it dont change.

What do you mean by "lets fuel right past it" ?? Fuel comes out the vacuum port?

[Ugod02010]

I think he meant it just flows right back to the tank. As if it's over pressurized.

Glad ur getting the help u need! I know what ur talking about, always get the do ls swap comments. Or just completely off the wall answers.

[Ugod02010]

What I'm reading that means ur fuel pressure regulator is shot.
If it's not the case try hooking the fuel pressure gauge back up and actually run the truck at full throttle and make sure the pump is keeping up. Just because the pressure is good at simulated WOT doesn't nesissarily mean it actually is when u do really get on it

[JKPhillips]

Ok guys what I found out was the FPR was bad I could clamp off the return line and BAZING!!!!! WOT all day long but it wont idle that way so I changed the FPR and its fixed. Now the gas gauge quit working so tomorrow is TAKE THE TANK OUT DAY! YIPPIE HOORAY anyone wanna help? lol Also the TPS (Part # TH51) that I bought is adjustable and wont work on a LT-1 regardless of what anyone tells you so thats a little info for whoever needs it. 93-97. .18v idle and 3.65v WOT Now its a paper weight.

[Ugod02010]

Awesome! Glad we could help! Now put up a burnout video!
I used to have a 83 s15 w/ a 355 carbed motor it was a beast.

[Ugod02010]

That truck was like scary fast! I used to burn everything that raced me. It jut had headers, little it of 2 1/2 pipe glass packs and right out under te doors. It was great

[popo8]

Whats goin on out back there?

LTXtech.com is my drug.

[Ugod02010]

Around 425 to 450 at te wheels. Plus a 150 shot just incase. I eventually put that motor into my 86z. I did spray the motor once while it was inthe truck, scared the shit right outta me! Said nope no more. It had edlebrock performer rpm intake, cam, and carb.

[Ugod02010]

Elcamino rear end! 4.56 gears

[popo8]

I take it the flares were easier than narrowing the rear. Sorry OP. back on track!

LTXtech.com is my drug.

[Ugod02010]

Way easier! Hey Larry did u see where I mentioned u on the thread about fans not working. Kid has it posted in the regional. I figure he would get more help in the regular tech section.

If u need to I understand erasing this post! Sorry OP

[JKPhillips]

Its all good leave the post lol truck is fixed now. I will post more recent pics tomorrow night and a burnout video if I get time to do one. Thanks guys

[popo8]

Its all good leave the post lol truck is fixed now. I will post more recent pics tomorrow night and a burnout video if I get time to do one. Thanks guys

You are a good sport man!

Just an LTXtech addict

[JKPhillips]

Pics tomorrow guys I promise. I dot know how to do the introduction to the site. I seen where some new members introduced hemselves and their vehicle? Got water in the Opti today and had major problems but its all better now.

[popo8]

No sweat man...

How are u visiting the site? Mobile... Computer...tapa???

Just an LTXtech addict

[popo8]

and.....how did u get water on ur opti?

Just an LTXtech addict

[Ugod02010]

Oh man. At least u got it straightened up! My luck I woulda been stuck buying a new opti

[beaver50]

I like this truck very nice.

[JKPhillips]

I am on a Laptop. No pics yet guys the new fuel sender and fuel pump went out. I think the pump shorted out on the inside and fried my sender so I had to send both of them back. I had the bright idea to pressure wash the engine (STUPID) and the rubber grommet is missing on the dist plug itself (didn't know that before hand) and walah hahahaha wet Opti. Thanks the truck was alot of work and continues to be lol The fuel pump hole in the bottom itself was closed almost all the way off. See pic#126120 This is what the Walbro pup looks like with the hole open ?26121

[Ugod02010]

Wow is that where the "sock" goes in the pump? What the hell happened?

[JKPhillips]

Not sure thats how it was when I pulled it out. I was in a hurry when I put it in and didn't think to look at that but I should have lol Factory defect. Its a KESHEN 250lph and they said it was ok thats how they all are. ????????????? Im going with a Racetronix or something of that nature.

[Ugod02010]

I have a autozone replacement in mine. I know for a fact mine is nice and open. That looks like it would impede the fuel flow for sure. Good to know to stay away from there stuff! Especially if they're all like that!