Code p0304 misfire 4

[kcfalcon2000]

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.

 

[05GTPcmpg]

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.

 

[kcfalcon2000]

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?

 

[SlowNA06]

Never hurts to ask.
You just hook up a fuel pressure gauge to the shrader valve under the black plastic screw-on cap on the fuel rail over the intake.

 

[kcfalcon2000]

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.