So right before I got my new transmission installed the vehicle was throwing a random misfire code. I cleared it out and then my new transmission was installed. I drove maybe a month to and from work. all was fine. then one day parked and running in the parking lot at work , it threw a random misfires code. i cleared it. and drove another week just fine. then again parked with the vehicle running at work and it threw a random misfires code. this time it started to run rough and it was a blinking check engine. i cleared it . and it was fine. weeks later..another random misfire code.cleared it and installed a new fuel pump this past weekend. fast forward to today on my lunch break.. random misfire code popped up again.. I cleared it... minutes later the code popped up again. I cleared it and I drove home from work fine.


Any idea what could be going on? This is only happening at idle.

 

Spark plugs?
C.O.P bad?
Rubber hose under resonator dry rotted, missing?
tb, maf dirty?
Cam actuator missing screens?
Air filter saturated or dirty?
Battery connectors hinky?
Catalytic converter plugged?
Tighten intake manifold bolts?

Just some random ideas.....

Chris

 

Year and mileage would help.

Everything Happy Hummer said.

Add you may have a coil on plug pack with a poor connection or on the fritz.

Have you changed plugs, and if so, how many miles ago?

 

2007 hummer h3 x about 54,000 miles now.

I changed the plugs recently and the coils. exhaust manifold is new. 02 sensors are new.