Random misfires only when it warms up... why?
 

My 4G64 2000 Galant misfires only when it warms up. The first few minutes of driving everything is perfect. Then about 10 minutes into the drive, when the engine temperature is about normal, it begins to misfire and just get worse and worse.

I just replaced all the plugs and wires and the coils, so I can't imagine its an ignition issue because everything seems totally fine when it's cold or warming up.

I removed the exhaust before the cat converter thinking the engine might not be able to breathe, and it still misfired.

Any ideas what might be causing it? The temperature specific aspect of it is what's so confusing to me...

RE: Random misfires only when it warms up... why?
 

Hey, I am having the same problems. Did you ever fix the problem?

RE: Random misfires only when it warms up... why?
 

Spark plugs, spark plug wires, or ignition coils.

RE: Random misfires only when it warms up... why?
 

Already replaced all of that.

RE: Random misfires only when it warms up... why?
 

Are you sure?

Check the ground strap on the alternator. Have you had problems with a dead battery lately?

RE: Random misfires only when it warms up... why?
 

No hard starts or dead batteries. The vehicle sat for a week and it started right up. I found out that she was using poor gas. 711, costco and safeway. Think the misfire may be a clogged EGR, but a little concerned about the tach jumping and going to zero. Not sure if I am working with an electrical problem or a sensor misreading due to something like the EGR clogged? Could also be a pin fit problem in the electrical.

RE: Random misfires only when it warms up... why?
 

Do you have a check engine light?

You seem to be fairly knowledgeable, so I have faith you will stumble on the issue. For now, without actually being there it is impossible to tell what is causing the issue.

RE: Random misfires only when it warms up... why?
 

Well thanks. Sometimes it is nice to brain storm or get ideas. Yes, I do have a po300 code which is a random misfire. It is wierd, because I will drive it down the freeway and soon after it gets to operating temp, I pull off the freeway and come back on the on ramp and it will studder and pull the light. Then it is fine on the rest of the freeway and will code again after getting off the freeway and going again after the stop. Thanks again. If you or anyone has an idea or a tip from a Mitsubishi tech. Please let me know.

Random mifire only after warm up
 

HELP!! Did you ever solve the random misfire problem? This s*#%t is maddening!

Random misfire only after warms up
 

Did you ever solve the random misfire problem? I could use some knowledge!