'97 5.4 recently developed a miss, checked the code, p0308(missfire cyl 8). After replacing the coil pack, spark plug, and injector, all from a good running parts truck it runs exactly the same. It doesnt always mis. While it's idling it only misses ocasionally. Higher rpm with no load it doesn't miss. It's only when it's under load. What else could it be?!?

 

Just replacing parts and stopping there is the error.
Is it the same cylinder again?
Did you change the last one at the rear of the driver side?
Are the coil and injector plugs on and locked?
You have to keep checking until your sure nothing is missed..

Last resort is to use a Scanner to look at live data and at the misfire monitors for info you cannot see otherwise.
Good luck.

 

Thanks for the reply.
Still the same cylinder, last one on driver's side.
It must be one of the connectors because I also replaced the ECM with no change.

 

Just for info, if the PCM driver for #8 coil was faulty or the lead to the coil is open you would get a code 358 not a 308.
If the injector driver was faulty that code would be different.
It's just something you missed or a coincidence one of the parts is also faulty.
Good luck.

 

Good to know.
I replaced the coil pack again and the connector that plugs into the coil and it runs great! Put about 8 miles on it and worked perfect the whole time.
Thanks again