1998 Chevy Corvette Idle surge?

LITERACOLA

MEMBER
1998 CHEVROLET CORVETTE

Engine Mechanical problem
1998 Chevy Corvette V8 Two Wheel Drive Manual 56XXX miles

I'm having an idle issue with my newly purchased 98 Corvette Coupe. When the car starts, it runs great, but once it gets warm, the idle starts to surge. It only surges 3 to 4 times and then levels out. Then about 30 seconds later, it surges another 3 or 4 times. What could this be? The car has an aftermarket cam, intake manifold, and various other goodies and was dyno tuned.

3 Replies

ERNEST CLARK

MECHANIC
1,730 POSTS

I'll need more information to help you.

Is your "Check Engine" light illuminated? If so, then you'll need to scan the computer to get a good direction on where to begin.

Was your computer reprogrammed to compensate for the performance parts? (New Chip) If not, then your computer will no longer be able to calculate the fuel and spark timing demands of your motor. Whenever you change the cam and intake, you're changing the breathing characteristics of your engine. This requires more fuel and a different spark curve.

If your computer has been reprogrammed, then the following can cause a surging idle:
Vacuum leak
Faulty IAC
Faulty Crankshaft position sensor
Secondary ignition problem (Spark plugs/wires/Coil)
Stuck/clogged fuel injector
Failing computer

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Thursday, January 7th, 2010 AT 6:27 PM

LITERACOLA

MEMBER
2 POSTS

There are no CELs. The computer was reprogrammed and the car was dyno tuned by the previous owner. I was even given multiple dyno sheets showing how the power increased as the tuning progressed.

The surging ONLY happens once the car warms up to normal temp. And what I thought was strange is that its intermittent, not constant. That makes it more complicated for me.

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Friday, January 8th, 2010 AT 10:23 AM

ERNEST CLARK

MECHANIC
1,730 POSTS

It's very hard to diagnose what's failing when there's no check engine light, and the problem is intermettent.

The only thing you can do is check the following:
Vacuum leak
Faulty IAC
Faulty Crankshaft position sensor
Secondary ignition problem (Spark plugs/wires/Coil)
Stuck/clogged fuel injector
Failing computer

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Friday, January 8th, 2010 AT 10:30 AM