Hi All, I'm a long time lurker, first time poster...I just picked up a 97 Corvette and I'm in need of some help. I had a local shop swap in a Siebert Performance LQ9, bored .40 over. I bought the car as a roller, so I have no previous knowledge of how it ran before or if it may already have a custom tune, etc. The local shop that did the install primarily focuses on Corvettes, but their specialty is really C1-C3's, they don't seem to work on much "modern" stuff (they've done great work on my C3). The car runs, but it will not idle at all. The tech that worked on the car didn't think that it would require a tune, as he said the ECM should re-learn the idle after 40-50 miles of normal driving. Well, 40-50 miles of driving have come and gone and this car just won't idle. You have to keep your foot into it just to keep the motor running and even then, it's really difficult to get the RPM's to remain steady. I'm assuming that this is due to the fact that the ECM just can't figure out the proper ratio's due to the increased displacement, bigger cam, etc. It's probably worth mentioning, the car is also showing a MAF code (high frequency interference), I swapped out with a new MAF and checked all of the seals on the intake and nothing seems to help. I'm curious if there are any tip/tricks that I may be missing to get this to idle? I've read about the idle re-learn process...would this work on a car with significant mods vs stock? Or is it safe to say that a tune would most likely cure this issue?

Thanks!

 

No matter what, you will need a tune to utilize your new HP. So don't waste time to get it to idle just get it tuned. I'm almost 100% sure that will take care of the problem. And don't just go to any shop. Find a reputable shop. JMO
Do you have headers, . You should be low 400 with new heads middle ish upper 400's.

 

GET A TUNE!!!!!! Still having 2 carburated cars myself, this isnt like swapping jets or turning a mixture screw to fix it. If you do not tune these animals even after a simple air intake upgrade it wont run right. Since you swapped over to a whole new engine with different cam, maybe different size injectors etc etc etc you need a tune. If you know nothing about the specs of the engine like if the reluctor wheel is a 28 or 56 tooth then definitely bring it to someone who knows tuning.

 

This^

So many variables in this, when you change one thing the stock tune can sometimes accommodate, but the more you change at one time and further away from stock tables you get, it just cant. Need to get it to a tuner.

 

Not to sound like a broken record, that car will never ever run right without being tuned by a reputable shop. And don't go to a peak number tuner. You are so far outside the window of the parameters of the stock PCM.

Nothing you will ever do at home short of tuning the car yourself with tuning software and the knowledge to do so, it will never ever run right or idle.

It also doesn't help much that you are running the 1997 PCM which is a bastard child. Kinda like trying to run an engine on an Atari 2600.

I honestly wouldn't drive it anymore until it's tuned.