Getting codes P300, 301, 306. Can't figure it out.
Jeep just purchased from guy who couldn't figure this out. 2001 WJ Laredo 4.0L. Now I can't figure it out either. New crate engine installed around 205,000 miles. Ran rough and threw codes. ATK warrantied it and sent a second crate engine. It does the same thing. ATK washed their hands of it and blamed install shop.
Previous owner replaced coils, wires, plugs, fuel filter, and a few sensors. No change. I think he swapped fuel injectors around. No change.
Jeep runs awesome when cold. Once it gets hot, CEL comes on and engine starts running like crap.
Took the valve cover off and all valve springs appear to be OK. Rockers are moving and are oiling just fine. It appeared the the rocker arm guide was backwards on #1 so unbolted it, turned it around, put it back on. Ran engine and seemed OK. Cleared codes and put valve cover back on.
Drove it today and ran like a champ until it got hot, then got #1 and #6 cylinder misfire again.