C4 Running rough.
Thread Starter
Instructor
Joined: Aug 2003
Posts: 109
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From: Milford CT
C4 Running rough.
I have a 94 Coupe 6spd. The car runs fine when I start it and take off. After a period of time I'll stop and it's running rough. If I blip the throttle it will stumble a little. When I take off it seems to run ok. When I get home and pull in the garage it's still running rough and the smell of a rich exhaust is overwhelming. I checked the codes and there are none. The check engine light does not come on. It seems that it runs fine until it hits the high temp, when the fan comes on but I can't swear to it. The next day it will do the same thing, run fine then run rough. A real stumper.
Oil Producer
Joined: Apr 2014
Posts: 9,349
Likes: 2,726
I have a 94 Coupe 6spd. The car runs fine when I start it and take off. After a period of time I'll stop and it's running rough. If I blip the throttle it will stumble a little. When I take off it seems to run ok. When I get home and pull in the garage it's still running rough and the smell of a rich exhaust is overwhelming. I checked the codes and there are none. The check engine light does not come on. It seems that it runs fine until it hits the high temp, when the fan comes on but I can't swear to it. The next day it will do the same thing, run fine then run rough. A real stumper.
Hi there. suspect injectors. can you attach a fuel pressure gauge to the rail and tape it faceing you in the driver seat and drive around to create the problem? if you see decreased pressure it may be an injector getting affected by the heat then opening wide open. you may see a pressure drop during this.
also do fuel leakdown test.
might also replace/inspect plugs. i've heard of cracked plugs that are affected by heat then start arcing. use dielectric (silicon) grease when you reinstall.
definately let us know what's going on with your fuel pressure during the rough condition and also do a leakdown then come back here and post results. cheers. VT.
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
Hi there. suspect injectors. can you attach a fuel pressure gauge to the rail and tape it faceing you in the driver seat and drive around to create the problem? if you see decreased pressure it may be an injector getting affected by the heat then opening wide open. you may see a pressure drop during this.
also do fuel leakdown test.
might also replace/inspect plugs. i've heard of cracked plugs that are affected by heat then start arcing. use dielectric (silicon) grease when you reinstall.
definately let us know what's going on with your fuel pressure during the rough condition and also do a leakdown then come back here and post results. cheers. VT.
also do fuel leakdown test.
might also replace/inspect plugs. i've heard of cracked plugs that are affected by heat then start arcing. use dielectric (silicon) grease when you reinstall.
definately let us know what's going on with your fuel pressure during the rough condition and also do a leakdown then come back here and post results. cheers. VT.
