Thread: Code p0304 misfire 4

I check other Posts and added to one but getting no replies so I will open this one;

I guess I got My BT interface / Torque reader just in time. Check engine light with the p0304 #4 misfire. After resetting will only come up if I accelerate hard / load up motor. Engine will "bump" "hesitate" what every you want to call, it a bit loading up ...on an incline trying to maintain speed or accelerate. If I down shift and get the RMPs up it smooths out. MPGs no change and normal on start, idle, and easy driving. 170k and R&R LIM, UIM, TB gaskets, plugs, coolant, oil 1200miles ago. Did a 0-60 check about 300 miles ago and was 6.7s. No mods. engine clean. 190 tstat and OBD says 199-210f with ac and 90f temp. Vac lines being shipped. SO I guess Injectors or ECM? I disconnected battery over night no change. almost forgot. MAF sensor changed 10 mo ago.

Okay well you know its cylinder 4 so that would be a good starting point. Check fuel pressure off of fuel pressure regulator. 4 cylinder is in the back middle of the motor closest to the doghouse. If fuel pressure is good, double check that plug and wire make sure its getting spark.

What is the best way to check the fuel pressure. OBDII on this does not have the data on fuel pressure. Would Oreily auto have a gauge I can borrow?

Ok finally got the chance to work on the problem. Ended up being a bad spark plug. When I went to remove the plug the top broke off of it, I initially freaked out thinking how the #$@@ was I going to get the plug out now until a split second later it clicked that the base was still good.>WHEW!! Any way, no mods 4 door 6.3 0-60 and a 14.95 1/4 mile with my 15 yr old son in the right seat, running much better. I also replace all vac. lines while I was at it.