I have an irregular misfire from my left bank in a SBC. the temp and RPM appears to make no difference. If I'm driving and it misses I can pop the gas and it clears up and then comes back..... Any suggestions as to what I should check? Steve
If you want to take the time.Replace one spark plug at a time. Then test the motor.If that doesn't do it.Replace one wire at a time.
does it misfire while idling? you could use a normal timing light and watch the flashes from each wire, that will tell you if it's the coil at least. Or gap your plugs smaller, if that helps then it's also the coil. [edit] temp not making a difference... might not be the coil then... Double-check the grounds to the block, make sure you got a 4 gauge wire on the back of that head.
If its left bank consistent, its really not irregular. X2 on compression test first What are you running for a distributor?
I appreciate your responses and I'll start checking it out in the morning .... No PVC, and the engine is a 68 ..up. It misfires when idling. It is irregular in that it isn't a constant, like you would get if it was one plug dead or a wire off.
I say compression test first so you rule out valves and head gaskets. Then you look for vacuume leaks, ignition, exhaust restriction....
Might be a vacuum leak . I would do the compression test and a vacuum test . You also might have a valve not seating good and causing that to happen . Check you plug wires , coil or ignition wires and leads for bare wires grounding out on the engine or something along that line . Does it backfire through the exhaust or carb when this happen es ? Retro Jim
. If its confined to 1357 them its something common there. What distributor / ignition system? New problem, old, dont know ? History? recent tune up Head, gasket, torque of the bolts, head****embly of that unit, valve adjusting on that side, plug wire mixed up,
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