C4 Intermittent Misfire
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6th Gear
Joined: Oct 2024
Posts: 6
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From: Livonia, NY
C4 Intermittent Misfire
I first posted this several months ago and received a rude response from some member who claimed it was was a "fish".
Trying again: I have. 1985 C4. Occasionally after starting it idles very rough. When driving it seems to "load up" and misfire. I take to my mechanic, it starts and runs well. He keeps a few days, starts it multiple times - no problem😩 I take it home and try starting it again. Same misfire problem. Any thoughts as to were to begin?
Trying again: I have. 1985 C4. Occasionally after starting it idles very rough. When driving it seems to "load up" and misfire. I take to my mechanic, it starts and runs well. He keeps a few days, starts it multiple times - no problem😩 I take it home and try starting it again. Same misfire problem. Any thoughts as to were to begin?
Melting Slicks
Joined: May 2014
Posts: 2,894
Likes: 592
From: New Port Richey FL
A little back History.
Last Tune up Plugs,cap,rotor- (a sticky gummed up plug will make a weak late cylinder) or a cracked cap or carboned rotor can make a weak spark. From cracked cap dampness in cap or carbon trail jumping spark.
Next have you put a pressure gauge on the fuel test port and see what your operating pressure is and if it bleeds down instantly, a leaky injector can make a wet cylinder that Fowls the plug (much like a lawnmower or dirt bike if it doesn't pop on first pulls)
How many miles on the car and does it puff smoke on first start after 24 hours (again see dirty weak plug)
Last Tune up Plugs,cap,rotor- (a sticky gummed up plug will make a weak late cylinder) or a cracked cap or carboned rotor can make a weak spark. From cracked cap dampness in cap or carbon trail jumping spark.
Next have you put a pressure gauge on the fuel test port and see what your operating pressure is and if it bleeds down instantly, a leaky injector can make a wet cylinder that Fowls the plug (much like a lawnmower or dirt bike if it doesn't pop on first pulls)
How many miles on the car and does it puff smoke on first start after 24 hours (again see dirty weak plug)
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,600
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From: Cape Coral, Florida
I first posted this several months ago and received a rude response from some member who claimed it was was a "fish".
Trying again: I have. 1985 C4. Occasionally after starting it idles very rough. When driving it seems to "load up" and misfire. I take to my mechanic, it starts and runs well. He keeps a few days, starts it multiple times - no problem😩 I take it home and try starting it again. Same misfire problem. Any thoughts as to were to begin?
Trying again: I have. 1985 C4. Occasionally after starting it idles very rough. When driving it seems to "load up" and misfire. I take to my mechanic, it starts and runs well. He keeps a few days, starts it multiple times - no problem😩 I take it home and try starting it again. Same misfire problem. Any thoughts as to were to begin?
I'd find a new "mechanic" preferably a diagnostic shop...general repair shops and dealerships only replace parts...good for them...bad for you !!
