ignition miss

[jeepdaddy65]

1972 CJ5 ,AMC 304 V8. Just wondering, what would cause a "miss" in the engine only after engine has been running and warm, especially at higher speeds and acceleration. When its cold and on initial startup its fine. Only thing I have done is change the spark plugs. Thanks

 

[007]

1972 CJ5 ,AMC 304 V8. Just wondering, what would cause a "miss" in the engine only after engine has been running and warm, especially at higher speeds and acceleration. When its cold and on initial startup its fine. Only thing I have done is change the spark plugs. Thanks

Well - off the top of my head (and assuming you're mostly stock)...plug wires, bad plug (even though it's new), coil, ICM.

Sometimes plug wires are fine until we go moving them around to replace plugs. They bend, they crack or break and when they get hot they expand and spark never makes it. Same is kinda true for new plugs. Rare but not impossible to get one that get's bad when it gets hot.

 

[jeepdaddy65]

Thanks, kind of hoping its the wires. have a new set coming in tomorrow. Does make sense, wires expand when hot, if there is a crack in the core it would maybe expand and lose contact when hot. hopefully new plugs are good, they were a real bear to get in. thanks again

 

[Lumpy Grits]

Get the engine started-Spray the spark plug wires with very soapy water. Do you get the miss? If YES-Your wires are grounding out. Get new wires. Don't go the cheap here.
If NO-Then spray the coil area. What's the results?
When is the last time you replaced the dizzy cap and rotor?
What spark plugs did you get and did you confirm the gap?
Did this start after the plug change? If so-you may not have a plug wire on securely.
LG

 

[jeepdaddy65]

Thank for the advice. I started it up at night and popped the hood, one of the wires was arcing, hard to believe, these are good 8mm wires that aren't that old. New wires coming in today, hope it solves the problem. Thanks again

 

[Lumpy Grits]

Fingers crossed.
LG