Misfire

[bigfoot72]

My 1972 Mustang Coupe w/ a 351-2v Cleveland has been having this odd misfire. Usually if i accelerate moderate-hard from a stop or up to 30mph the car will "cough" 1-3 times, basically losing acceleration for a brief second. But when i am driving on the freeway the car is fine. Also at a stop the car will run a little bit rough, which got me to think it is a misfire. When i changed the spark plugs about 1 year ago i noticed on the number 4 plug it had quite a bit of carbon deposit on it. I checked it the other day and it seemed fine, but one of the plug wires might be broken. The passenger side exhaust smokes a bit too. Could the reason for this misfire be the plug wire? Or could the valves be dirty? Any easy or cheap remedies that could help.

Thanks,

-Zak

 

[Omie01]

I would check for intake vacuum leaks, my Cleveland last year started sucking oil into the heads and it caused a heavy buildup on the plugs in those cylinders and caused it to run rough. It was causing some bluing of the exhaust on that side also. Just something to check.

 

[will e]

misfire sounds possible. Do you have a timing light? You can check each wire while it is idling to see if they fire consistently. Even better if your timing light has an RPM output.

 

[c9zx]

The hesitation when accelerating sounds like an accelerator pump circuit problem from what you have said. If you have a timing light, you can move the inductive pick-up from wire to wire to see if there is one that doesn't consistently trigger the light flash. You can also use an ohmmeter to measure the end to end resistance of each wire as well as the posts on the distributor cap. As for the light smoke, I'd start with a compression check or a leak down test if you have access to the leak down tester. Let us know what you find. Chuck

 

[72HCODE]

electronic ignition or points?

 

[bigfoot72]

Pertronix Ignition

 

[Vinnie]

Could the reason for this misfire be the plug wire

My other car (four cylinder Opel Corsa) suffered misfires. I thought "what can be wrong with a wire?" but I changed the plug wires anyway and guess what? Haven't had a misfire since! It's all I did.

No guarantee for your case but yes, it can be the wires

 

[IA Rider]

Could very well be a plug wire. I would start with plug wires then spark plugs. I had a similar issue years ago with an F250. Ended up being a spark plug.