Ok, changed out a bad EGR, checked for vacuum leaks, plugs & wires only have 700 miles on them, injectors are good. Im thinking ICM or coil, make sense?Lean idle misfire

Hi and welcome to the forum.

What year car are we talking about here? What other history is there? The more info you can provide, the more we can try to help.

Matthew

I imagine this is an old thread but grounds on Ign wiring harnesses are a problem and the wrong coil or a weak coil are other possibilities.
Usually this happens at a specific RPM range .
Modified computers or Ign systems wired in are other components.
These computer cars depend on good grounds ! Need I say grounding is a sensitive subject on Corvettes !

Ya really have to detail what you have to get detailed help !

I have a 92 base model with 120k, have had it for 2 years and know it very well. I autox it and have started to do some hpd. I have done a lot of work on it the last year and now need a couple new cats. I'm getting an intermitent miss at idle only,otherwise it runs great. Changed a bad egr checked for vacuum leaks injectors are good and plugs & wires changed a short time ago.

Have you checked for any codes? Are you sure the wires are completely pushed on the plugs? Did you double check the wires / ohm test them? Try starting the motor in a dark garage to check for arcing. What condition is your opti in?

How's the fuel pressure?

This could be electrical or fuel related.

Also, how do you know it's misfiring?

Matthew

Quote:

ThunderHill?

What Matthew said, pull the codes. If you haven't done it, the procedure is in our Tech Library.

Please describe the miss. Also why you think it's a "lean" miss.

Was it idling at a dead stop? Or did it hickup at idle in a parking lot? My 92 was doing that (very intermittent) before the opti went.
Has the water pump ever gone out and flooded the opti?

Welcome to the forum.

Kimmer - welcome!

I have a 92, also, and they are noted for a bad idle. Did you pull the fuel rail and check for flow? If one isn't flowing quite right, then all hell breaks loose. If you need new injectors, I highly recommend a match set from FIC. That's what I have, and they have been in for about 2 years now. Run real good. And a matched set will run better in these bank-2-bank systems we have.

Considering the mileage, valve burn is a concern. The LT1 isn't immune to it... never can tell.

I do feel the ICM harness and hardware is a place to really check. If the ICM is bad, things will get worse as the engine warms. I have also seen harnesses fail at the ICM, causing all sorts of weird things to happen.

If you need new cats, Random Tech makes great ones. Magnaflows are pretty good, too.

Hey Kim. Welcome to Corvette-Guru. For those of you that don't know kimmer, his C4 Corvette is featured in an article in the July issue of Corvette Magazine, page 63. Glad you stopped in. Hope we can be of assistance.

ooh... I need to check that out!

I pretty much have gone through it. No codes, new coil and ICM they were free replacement from autuzone. Bad EGR was changed out and other than the lean idle it runs tops. Plugs & wires changed recently and I know for a fact I need new cats so I will change the 02 sensors at the same time.I will check the grounds this weekend.

Hi welcome to the Guru! I read that article, sounds like you bought it right. Nice car!

02 sensors can cause problems at idle. I would recommend NGK when you replace them.

Matthew

Beautiful car. I would check fuel pressure and ohm check your injectors both cold and hot.

There is a video on how to ohm test them in the FIC forum in the video thread.

~Rich

Thank's everyone, will check it all out. Kim.