Hunter71495

Got a 2005 5.4 crew cab a few months back. Started to have a random misfire/jerk to it which i thought was a coil pack going bad. Was making noise at 117k miles, replaced timing kit, cam phasers, coil packs, plugs. Turns out i had a broken timing chain guide on the upper passenger side. Well got it all back together after breaking all the passenger plugs and getting them all out. Broke my fuel pressure sensor when putting back together so got a new one of them oem. Built oil pressure before starting it and fired it up and it ran rough, had a low idle at around 500rpm's, and found i had a cylinder 6 random misfire. Changed out coil packs to another brand new one, checked spark plug for spark, bought a new injector and switched cyl 6 injector with cyl 5 thus testing the new injector in cyl 5 and using the old injector which i know is working in cyl 6. Checked power with a mulitmeter to the injector and the coil pack, cleaned my maf, cleaned my throttle body which cleared up my rough idle for a little, changed fuel filter. Tomorrow its looking like she is getting a compression check. I tried disconnecting cyl 6 injector and coil pack and driving with a completely dead cylinder and then tried pluging it back in and there is a difference. The cylinder is NOT completely dead. It seems to have a sequence to the missfire. 3-5 misfires for every good fire on that cylinder, the rest seem to be working well. Sometimes its very noticeable other times not so much, seems to be worse in drive than 1 or 2. Idle is low again. Any ideas? 19 year old here and pulling out my hair trying to figure this out and really do not want to go to a shop. Would rather figure it out without paying a huge bill. About ready to throw in the towel on this truck. Please help. Thanks

Mod (Ret.)

When you changed the plugs and COP's did you also replace the spark plug boot and springs? Many here have reported that the spring inside the boot does not make good contact with the spark plug. Not recommending you change them (tossing parts to fix a problem gets costly), but may be something to consider as a misfilre/jerk possiblity.

Hunter71495

Yes sir, they came all in one with the boots, springs, cops. Everything new, I'm going to buy a spark plug just to be 100% sure its not a spark plug acting up and throw that in, grab a new gas cap and check my fuel regulator back by the spare tire. Next step i think then is hopefully get it in for a compression check today and then after that i was thinking maybe a blocked cat depending upon the compression check? I'm at the point of throwing money into it and i don't really care, ill replace whatever i have to if it means i don't have a $20k paper weight running on 7 cylinders. Besides its maintenance anyhow right?

Mod (Ret.)

If it's running only on 7 cylinders, you can rule out the FDPM or gas cap; they would not effect just one cylinder.

lewissa81

Did you use a lot of antiseize on the plugs? Too much can cause a misfire.

I think the compression test is a great idea also.