please help P0300 + p0305 + p0307

[lswjth2]

Hello . I have a 01 GC 4.7l v8. The other day, the car started up and it was idling really rough. I drove it for two blocks and the check engine light started flashing and then the jeep died. It would not start after that. After 15 min, it started again, but was idling really bad. I hooked up a scanner and got error codes P0300 + p0307 +p0305. Sure enough,I
removed the connectors for those two coil packs and no difference. So i replaced the # 5 cylinder coil pack with the # 1 cylinder no change? The plugs are about 500 miles old. I took it to the dealer and they have replaced the PCM, the coil packs and the fuel injectors for those two cylinders and no change. They want to tear the engine apart?? Any ideas?? Thank you

[Bob D.]

Those codes aren't much help to anybody eg. P0300- Random/Multiple Cylinder Misfire Detected.
With those repairs I hope its still under warranty.
Some others may have some ideas but until then stay away from the dealer, they really sound like they don't have a clue. Try an independent mech.

[theFREAKnasty82]

P0305 & P0307 is misfires for cylinders 5 & 7. Has anyone checked your intake manifold gasket around those cylinders to check for leaks? Unfortunately, the dealer only pays its techs for the amount of time it takes to fix a car, not to properly diagnose it. That's why they just throw parts on their b/c techs don't make money diagnosing, they make money just replacing items, blindly guessing the problem. You say the plugs have 500 miles on them, were they properly gapped? Also go to a shop that come pull up vital information on the condition of the injectors, such as getting short-term and long-term fuel trims. I think your problem might be fuel-related in that you have carbon build up on your throttle body and also carbon build-up on your injectors. Try this, go to Advance Auto Parts and buy a bottle of Lucas Fuel System Treatment & Upper Cylinder Head Lubricant. It's concentrated and highly effective and can clean out any carbon buildup that's on your injectors or upper cylinder head.