C4 running problems help me!
Thread Starter
Advanced
Joined: Mar 2009
Posts: 51
Likes: 0
From: Hamburg N.Y.
C4 running problems help me!
I have a 1994 C4 w/13,000 miles.Good Battery & gas.
Problem is after warm up it starts to miss and stalls out.
On restart which is hard it starts to backfire.
Could this be the OPTI SPARK??
Please Help,Tks
Team Owner
Joined: Mar 2001
Posts: 66,675
Likes: 86
From: Santa Cruz CA
St. Jude Donor '15
This is from the C4 Tech/Performance section. Scroll down to the Opti Spark section. Not sure if it will be a fix but may lead to it. 
http://forums.corvetteforum.com/c4-t...lar-basis.html
http://forums.corvetteforum.com/c4-t...lar-basis.html
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
That said, is the water pump leaking? There is a diaphram in there that can dry rot on barely/never driven cars, they leak from the weep hole onto the opti.
Otherwise, my first guess is the Ignition Control Module. Perhaps the heat sink grease has dried out and the ICM is overheating. First way to check, is to test for spark from the coil during the event. Or to remove the ICM, very easy, and take to auto parts store to test.
Also look for signs of fuel in the vacuum line from the fuel pressure regulator, again, a diaphram inside.
Intermediate
Joined: Jun 2012
Posts: 41
Likes: 0
From: Hamden CT
My 93 was doing the exact same thing before I put it away for the winter. Mines at 28 k and was praying it wasn't the opti. My mechanic took it for a few days and was able to fix it. ICM. May need a new one. He cleaned the connections a bit, plugged it back in and wahla car runs beautifully so far...we will see this weekend...I will order a new ICM just in case 
Burning Brakes
Joined: Mar 2005
Posts: 800
Likes: 2
I guess you would just say my car should be brought straight to the junk yard then? It is a '93 with 103k on it.
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