Car won't rev past 2.5k, idles above 1k.
 

Hey guys. Fully built bottom end and supercharged here. Techs are stumped. Weird thing keeps happening where the car won't rev past 2.5k and it idles just above 1k. I looked around and saw one thread on it but it doesn't help. Any ideas? I have a 2010 manual G coupe. I replaced the ECU and the VVEL controller and the issue is still happening. ECU was an exact match (2010 manual coupe ecu).

Have you tried talking to your tuner about this issue? It seems like it is in limp mode.

I've run into this issue a couple times when I first started tuning the supercharger kit and when I went with Topgunz A-A setup. Goes into limp mode. The tuner should be solving this issue.

My tuner said to check the extension harnesses for the TBs and MAFs.

Ah, so you have the Stillen Supercharger setup.

Yeah I listed all mods in OP.

Yes!
My TB extension harness still gives me limp mode at random/unpredicable times and has for years now. Might be fine for 6 months then plays up 2 or 3 times in a shorter (days/weeks) succession.
I still don't believe there is a proper fix for this including replacing the ext harness with a newer (upgraded) one from Stillen. Very annoying and unsafe! :mad:

Limp mode is where the car has almost zero throttle. That's not the symptom I'm having. I'm having a symptom where the car idles above 1k and won't rev past 2.5k.

Limp mode is a general condition where the computer reduces power of the engine. There are various causes. You might see revs limited to 5K RPMs or 3K RPMs or less depending on the cause.

Right but it also makes the car rev super slow. That's not what I'm experiencing. My car revs at normal speed. It just caps at 2.5k and idles above 1k. In limp mode, the car revs really slow through every gear. That's not what I'm experiencing.

Not true. I've had limp mode hit me on the track due to oil temps and limit me to 5K RPMs. Other than the rev limit reduction, there was no perceptible change in throttle input or driveability. There are various levels of limp mode - you are referring to a more extreme condition. But still a version of limp mode.

Engine codes?

OK. :tup:

So I replaced the extension harness with a brand new one yesterday. So far so good. No issues at all. Drove the car for 10 minutes. Shop is going to drive the car for the next few days to make sure everything is good to go. Will post update if anything happens.

No codes at all.