I got a cel a couple weeks ago and read it and it told misfire #8 cyl...So i replaced it with an old mc coil i had and it ran fine for a couple hundred miles maybe and then started again, so I bought a new mc coil and installed it on the #8 cyl and again, after a couple hundred miles, I now have the truck on another low grade...bucking, jumping ~40-55 mph. I also checked the injector and it is pulsing... but no cel yet...Anyone know if there's anything else this miss could be coming from? Seems like she likes a different/new coil every couple hundred....

 

Did you pull the spark plug and look at it?

 

Yes, I pulled the plug and checked the gap and it was still at .54.....The plugs only have maybe 1000 miles or so on them..and it LOOKED like it was ok....Could it be the near new plug being the problem? Thanks.

 

What brand is the plug?

 

I had a new plug go out after only 5000 miles. Pull the plug but leave the coil on the plug. Ground the plug and fire it up. You should see the plug firing. Mine wouldn't do anything.

 

If you are going to do that, also disconnect the fuel injector for that cylinder.

 

mc, always.
So actually start up the truck and let it run? Thanks.
Thanks.

 

Bump....I pulled the coil today and put a plug in it and it is getting spark....So i have in cyl #8: near new mc plug, new mc coil, a swapped injector with a cyl that is not misfiring...And i still pulled a p0308 cyl #8 misfire code today before i swapped the injector though. So i swapped injectors to see if it will follow... It ran fine after i put the new mc coil in, a couple hundred miles ago and then just started misfiring again and threw this code again...Anything else it could be for cyl #8 to check? Thanks.

 

If the plug, cop and injector are tested to be good, compression would be the next check for me. I would swap the cop to another cylinder and see if it follows. Could just be a faulty cop.

 

I'd try a different/new plug. You can still get some kind of spark from a plug that isn't necessarily firing properly or that, for example, has a crack in the insulator, etc. Assuming that a part is good because it's new has caused me wasted time more than once.

If you still have a problem on the same cylinder after swapping/replacing, then you might also check the connectors for the coil and injector. Unusual but could be a problem with the connector or wiring itself (e.g., somebody pulling on it too hard causing a bad connection).

 

Thanks. I can swap the cop but I had a global in and it also threw the same code, same cyl, which is why i bought a brand new mc one and when i first installed it, it ran fine. Ill give it a try though.

Alright, i can throw a brand new plug in just to make triple sure. I looked at the wires for the cop and injector and they seem to look ok up to where they bundle inside the harness.... Thanks for the help.