Should I just drive the car off a cliff? I need help

[Joker Z28]

It seems like I will never get this car running right.

Long story short I ended up towing my car to a shop about 2 hours from where I live to fix a few leaks and tune the car.

While at shop to fix a few leaks ended up with me getting a new optispark and water pump, its leak free now but cannot tune.

It seems like at 4.5 RPMs it missfires like crazy. It dynoed even with the mis-fires a very weak amount of power compared to what it should be.

Before going to the shop I made a few adjustments on the motor and realized I was never able to go WOT, a clamp on the CAI elbow prevented the TB from going down all the way, since I have fixed it, it went straight to the shop so I dont know how long my misfire has been there.
If I am not getting on it I can climb the RPMs just fine but only at WOT it acts up.

Its got fresh plugs, the wires are good, its got a fresh brand new opti. What else can I check or see how to fix this? I really want to get tuned
Thanks in advance.

[95formula383lt1]

just cuz the opti is fresh doesnt mean its working good. I just had a similar problem with one that was brand new. I was pissed. Is the ICM good? as well as all other sensors like MAF an MAP, perhaps data logging could explain things better.

[Joker Z28]

How can I check the ICM.

The guys at the shop couldn't be more specific, they said its defitantly something with igntion. I really really really really really hope its not an opti because It would be number 4 in less then 6 months.

[Joker Z28]

Datalogging is not something I want to do at this point, I would like to get rid of opti.

[Joker Z28]

Ok so what can cause misfires at 4.5+RPMs at WOT but at half-3/4 throttle it would climb the rpms fine?

[95ImpySS]

Fuel pressure? Is the car modified? Data logging is easy. Any reputable shop should have a SnapOn scanner which will read and sometimes datalog real time data.

[BIGT94z]

im also curious of the fuel pressure. how is the coil/icm? any locals near you have any spares for you to test?

[Joker Z28]

All these "good shops" around here are about 2 hours from where I live so its not a simple task.
Car is slightly modified, just a forged h/c/i 383.

When it was on the dyno the tuner said everything seemed fine, fuel was ok.
He said for sure its something in ignition.

My question is, where in the ignition would cause the misfire only at WOT past 4.5 rpms but at part throttle it would climb the rpms no problem.

Other then that, the car drives around just fine until wot

[popo8]

Dude, its kinda like the same problem Ive been chasing for years....


5100 RPM with my MSD opti......

we ruled out fuel,

then we thought it was the MAF being maxed out....

so through frustration, I purchased a dynaspark opti, and am in the process of fighting to get one that is 100% out of the box....

Anyways...... I dont know where I was going....

[95ImpySS]

Tune related????

WOT will call for alot more power from the coil, ICM, opti etc. Could have a weak wire or bad ground causing the voltage to these components to drop and create a miss. I would watch your spark advance with a proper scanner in real time. If at all possible data log and go thorugh it and find drops or spikes.

Watch your TPS, MAP and MAF values to make sure your getting WOT.

Has the car worked fine since mods or is this a constant problem since modification?

[Joker Z28]

Never had the problem till new motor.
But that is also kinda hard to say, I never noticed till the car was down for opti and water pump replacment that I never was able to go WOT.
The TB was hitting a clamp holding the elbow on the CAI. Before it ran fine at WOT but then again it never really was WOT I was at 50%

[Joker Z28]

Popo, I guess LT1s also give trouble to anyone in the criminal justice field haha

[Joker Z28]

So any tips to figure out how I can go on finding the problem?

What should I check for and how?

[Joker Z28]

New info, I have a code for a bad crank position sensor/circuit.

My car still cranks and runs ect. ect. but has the problems described above, could that sensor have anything to do with it?

[speedracer2536]

yes it def. can.. It varies car to car.. Some i have seen run with a bad cps.. Some just fall on there face.. I would replace the sensor/ or depending on if you did a cam swap you may have either forgotten the reluctor or installed it incorrectly

[Joker Z28]

What is the CPS and the reluctor?

Yes there was a cam swap as well.

[Joker Z28]

Another update:

Replaced the crank position sensor and it changed absolutely nothing.
Check engine was still on, and a P1441 code came up, I am not sure how long that has been up there.

Does that sound consistant with any of my problems? Also while at the dyno, the shopped deleted my EVAP because I took it out a while ago. I do want to say I had this problem before my SES ever came on.

[Joker Z28]

B to the UMP

[Joker Z28]

Not even a repituable shop can figure it out.
I have lost all faith in the LT1s

[bidicamaro]

When they replaced the opti did they also replace the cap and rotor? I also had a similar issue and noticed that my coil was arching to the square thing that surrounds it (haven't the slightest on the name of that thing?) Got a new coil and was fixed for a bit. Then, once warm would start doing the same thing. My #8 wire was bad so replaced the wires. Worked fine for about 2 days then my #6 wire was haveing an affair with my PS pully so I replaced that wire and used an abundance of zip ties to hold them correctly. On any note, I had a similar problem everytime. Would ride pretty decent until WOT. Pop the hood in the dark and look for the "lightening storm" in the engine bay.

EDIT: my $ is on the cap and rotor...

[Joker Z28]

Yea the whole opti was replaced including the cap and rotor.