Tuning a car this weekend, PTE 6266, built 2.0, ams intake mani, a full build... Tuning the car on stock ECU, if we hit the rev limiter, the car would go into some sort of limp mode. When this happened the car will misfire badly and act almost like anti-lag, or like a coil is going out... in turn fouling the plugs badly. Replaced ignition coils with no change, replaced cam sensor and the problem got much better, but still getting some missfiring at higher RPM. Any thoughts or anyone had similar issues?

 

I would double check the resistente on your maf sensor or make sure ur coolant temp sensor is workin properly.

 

Did the misfiring happen after the run or were you guys spanking the rev limiter?

 

The bad missfires would happen after spanking the rev limiter, it would eventually clear up about 2 minutes later... here is the strange part... once it would start misfiring, we could turn off the ignition and restart the car and it would be fine... so freaking weird...

 

I had a VERY similar issue with my last project car. After spending too much money replacing just about everything electrical on it, I gave up on the project. When it does misfire at high rpms, is it shutting the car off?

 

Sometimes the car will die, mainly due to the horrendous misfire issues...

 

Does the vehicle have a COP setup on it?

 

I had the same problem with my car change ignition, tried different pumps it end up being the wire going to the map sensor came loose. Rewired it and bam problem solved!

 

Thanks s.e.a.n. will take a look at the wiring this weekend...

Yes has a sparktech CDI for stock ecu, however swapped with known good oem coils and had same issue...

 

Valve float. What springs are on the car? The lifters pump up once the valves float slightly causing a misfire and poor compression. Turning the car off allows the valve spring to close the valve and compress the lifter and then it will run ok.

 

^^^ +1 I think this is the problem. Almost the exact same thing happens with mine above 8100 on stock springs.

 

Guys the car is fully built, it does not have stock valve springs in it... GSC S2s and GSC Beehives, so that rules out valve float...

 

I wouldn't be so sure it definitively rules it out. Not in an Evo, but I have seen this before in another car with brand new springs. At least it is something to re-check when everything else checks out. Good luck with it. I know these things can be pesky.

 

I would not assume that just because it has springs in it that they aren't worn out. A few guys on rev limiter can really wear a spring down fast. A spring that was being worked hard could definitely be losing control of the valve. How new are the springs. Many domestic guys replace springs on a regular basis because they are a consumable.

 

Freddie every time I have seen the issue you are describing it has 9/10 been the cam sensor.

You said you put a new one in it. Try pulling the battery cables off for a bit.