[Est98SS]

A few months ago, my car started to misfire at WOT around 5k RPM and cause the CEL to flash. At the time, the car just had bolt ons and a flex fuel and it would happen when I used e85, when I used 91 I could still hear the misfire at high rpm at WOT but it wasn't as bad and it didn't cause any CELs to flash or come up. Found it to be a burnt plug wire in cylinder 2 and replaced it and it seemed to run fine.

After that, I had a shop install a pro charger kit and after the install when they went to tune it, they ran into cylinder 2 misfiring again under WOT. They checked the plugs (NGK), plug wires, and coils and replaced the plug and wire for cylinder 2 but it didn't help. They tried a leak down and compression test in case of any engine damage but it turned out fine. They assumed it had to be an injector but after I talked to other shops with more experience with LT1s, none of them really believed that could be the problem and thought it was more likely that it was a bad tune.

I ended picking up the car and bringing it to a more experienced shop to look over the install before I brought it to a better tuner. They looked over the wiring and the install and even looked at the valve train for a bent pushrod but found nothing wrong. They also did a leak down test and found nothing. Finally, they tried unplugging my MSD 2 step and that seemed to make the car run smoother but it still misfired under WOT. At this point they believed it had to be a bad tune so I went to one of the more reputable NorCal tuners and even he couldn't solve the issue through tuning and he said its got to be something electrical or mechanical. I ended up bringing it to a mod friendly dealership and they looked everything over and tried replacing the injector on cylinder 2 but it didn't help. At this point they're saying its got to be the tune or engine damage but even they are familiar with my tuner and trust his tuning so they are going to try another leak down and compression test to try to pinpoint the issue before spending a bunch of money tearing down the engine.

Any ideas to what it could be? The car runs perfectly fine at partial throttle all the way to redline but at WOT it starts to break up right at 3500 RPM and they’re seeing the misfire mostly in cylinder 2. The only codes they are seeing are p0121 and p1101.

[Dysan911]

There were and perhaps still are issues with the MAF Extension wire that Procharger supplies. The pins in the waterproof connector can misalign and end up pushing one or more out of the connector leaving a few pins disconnected and cause all kinds of issues. Not sure if it's related to the problem your having but I would definitely check that out.

[KingLT1]

spark plug gap?

edit*
I just noticed the codes you mention are TPS voltage and MAF related. I will say engines can be picky about extension harnesses which I believe you had to use for the procharger.

We had to uses a IAT extension harness on my brothers 96 Z28 and he had been randomly getting a check engine light. I found out the weather pack connector on one end of the extension harness was junk. So we hardwired the extension harness and problem solved.

[Juiced1]

If you are running a MAF and TPS code I would look into having the dealer or a tech with a scan tool re-calibrate those sensors. If they are off you will have issues

[Est98SS]

Originally Posted by Dysan911

There were and perhaps still are issues with the MAF Extension wire that Procharger supplies. The pins in the waterproof connector can misalign and end up pushing one or more out of the connector leaving a few pins disconnected and cause all kinds of issues. Not sure if it's related to the problem your having but I would definitely check that out.

I had read your thread about the messed up extension harness before I had brought it to the second shop so I had him look over it but he said the pins looked fine. Ill mention it again to the dealership that its at now and see what they say.

Originally Posted by KingLT1

spark plug gap?

edit*
I just noticed the codes you mention are TPS voltage and MAF related. I will say engines can be picky about extension harnesses which I believe you had to use for the procharger.

We had to uses a IAT extension harness on my brothers 96 Z28 and he had been randomly getting a check engine light. I found out the weather pack connector on one end of the extension harness was junk. So we hardwired the extension harness and problem solved.

The plugs are gapped to 0.030.

I have an IAT/Baro breakout as well but I never installed it so I think the only extension in place currently is for the MAF.

Originally Posted by Juiced1

If you are running a MAF and TPS code I would look into having the dealer or a tech with a scan tool re-calibrate those sensors. If they are off you will have issues

The car is currently at a dealership that deals with a lot of modified cars but they hadn't mentioned anything about that. Are you saying to ask them to recalibrate the TPS and MAF sensors?

[Est98SS]

Also what is weird about this is the misfiring is occurring in the same cylinder that had the burnt plug wire but we have replaced the coil, injector, plug and plug wire and done leak down and compression tests showing no damage