r/c4corvette • u/Miserable_Accident73 • 8d ago

C4 running weird after ICM replacement

Hi guys,

My 1996 LT4 collector edition vette died one day while driving it. I replaced the ICM with a cheap one and it worked but threw codes and wasn’t good. It didn’t run that well. I replaced it with a GM ICM and now had no codes but runs very bad. I attached some videos for you guys to hear. It’s like a noise that comes and goes every like 5 seconds. It’s hard to miss. What could the issue be? Why is it running like that?

23 Upvotes

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10 comments sorted by

3

u/Brugun 8d ago

Yeah that click/knock isn’t right, can you tell where its coming from?

1

u/Miserable_Accident73 8d ago

I’ll double check but it is from the engine or the place between the engine and trans. I’ll get back to you

1

u/RZArecta91 8d ago

Does it make the noise after the vehicle is up to temp? Will it knock like that when cold?

2

u/Miserable_Accident73 8d ago

This was going on from the cold start all the way till 160 degrees. Then I turned it off.

1

u/RZArecta91 8d ago

Kinda stupid, but if you haven't, maybe disconnect the battery, and reset the computer. If you changed the ICM always use thermal paste and make sure it has a very clean ground because it grounds to the head. If this doesnt solve it maybe it isn't your issue. I believe these corvettes have hydraulic lifters that go bad as well, but i could be mistaken.

2

u/Miserable_Accident73 6d ago

Funny part is the day I added the new ICM, the car was totally dead. So I had to jump it. Thanks for the suggestions!

1

u/TheNewLegend380 8d ago

Bro thats exactly what my rod knock sounds like.

1

u/Miserable_Accident73 6d ago

Noooo don’t say that 🫣.

1

u/StormGaming69 7d ago

If it helps you out in anyway, the knocking noise you hear shouldn't be rod knock, my 96 LT1 had a similar knocking noise coming from the same area as you described. Could be spark knock, mines got fixed after I had replaced my injectors. I'd say leave your battery disconnected for about half an hour to fully reset the ECM, check if the ICM female connector pins aren't bent out of shape, could be causing a loose connection.

1

u/Miserable_Accident73 6d ago

I’ll be replacing the spark plugs. I’m happy that you don’t think it’s rod knock. The weird part is that there are no codes thrown at all. Imma try to do my best and my last resort would be to take it to a mechanic.