Misfire
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Heel & Toe
Joined: Oct 2024
Posts: 22
Likes: 3
Misfire
Hi guys, I bought my c3 a few years ago and have been replacing parts as I go along but have a problem which I hope you can answer.....I have a miss fire on one cylinder which I believe is #6...the plug is sooted but not fouled, all other plugs look good (all new)...new wires, dizzy cap and rotor...I noticed some black shooting in the inlet manifold at #6 inlet port... when hot it seems to run fine on idle but when driving/acceleration there is this miss fire...no smoke from the exhaust and no blow back through the carb, anyone had this problem?....any ideas guys... ignition faults maybe?..I don't know what can be causing the problem... thanks guys in advance..
Safety Car
Joined: May 2001
Posts: 4,761
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From: Fairfax Virginia
Welcome to the Corvette Forum, 78silveranni! This the right place to be when you have questions or issues with your Corvette.
For your issues it would be good to run the engine in the dark to see if there are any sparks under the hood. Have you checked the compression of the engine yet? It would be interesting to hear what the compression numbers are. Have you tried another wire of plug on the #6 cylinder.
I am not sure what kind of gasoline you are using, I like BG 44K fuel system cleaner and it does a great job cleaning the carburetor or on a fuel injected engine. Let us know what the compression test shows as that might highlight the #6 cylinder having lower compression.
For your issues it would be good to run the engine in the dark to see if there are any sparks under the hood. Have you checked the compression of the engine yet? It would be interesting to hear what the compression numbers are. Have you tried another wire of plug on the #6 cylinder.
I am not sure what kind of gasoline you are using, I like BG 44K fuel system cleaner and it does a great job cleaning the carburetor or on a fuel injected engine. Let us know what the compression test shows as that might highlight the #6 cylinder having lower compression.
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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If the plugs and arcing inst the issue there are a few other things I have had in the past
- bad plug wire...either the end came off in the boot and it isnt getting good spark or the wire melted through sitting on the header.... put a new plug in it, run the motor and unplug the wire if there is no difference, then swap the wire and check the cap
- bad cap...Ive had a cap get cracked and it would arc through the cap, heating it up either fixed it or made it worse. check the cap and rotor for wear and check the cap to see if the rotor is eating into the cap. Also had a distributor lose a locking ring and it was working its way up into the cap...lots of misfires with that as the higher it climbed the more the timing changed...it will cause multiple misfires
- youve got a leak in your intake gasket right at the number 6 runner. Ive had that issue sucking oil into the intake. I sealed the new intake gasket with permatex no. 2 https://www.permatex.com/products/ga...-sealant-3-oz/
