First off this is my first post i believe i am in the correct section if not my apologies.
about a year ago i bought a 2000 grand cherokee 4.7 for a fair deal, or so i thought. knowing it had a "blown head gasket" i proceeded to purchase the vehicle. After pulling the heads off the passenger side head was done for, so instead of taking risk buying a new head and putting it back together i went ahead and ordered a new engine(assembled), 0 miles so i felt that it would be a smooth problem free vehicle engine wise for a while. well i was wrong. after getting the engine in it ran AMAZING i loved it and for what i paid i couldn't have been happier. a few days later i took the jeep on a road trip to see a show about two hours away all highway, constant 70mph not beating on it because it was new.
on my way back i had a check engine light come on, i was so close to home (5 minutes away) i just went on home scanned the code. it came up as a cylinder 4 misfire. i assumed coil pack and/or spark plug. replaced the coil pack and plugs, it was still there. so we started playing around with it. moving injectors and coils to see if the code would follow, nope stayed on cylinder 4. after brainstorming, we proceeded to test the connections to the coil and it was receiving power. now i have a jeep with a cylinder 4 misfire and rough idle. with no other vehicle my only option was to drive it. (i'm a student and i work no other options) i found this forum and I've been on here as a guest about 100 times looking for answers via search. i found it could be the crank position sensor or cam position sensor. replaced both with autozone parts. no go still a misfire on cylinder 4 and it was the ONLY code. after researching more and more i found jeeps like oem sensors. well off to the dealership it was, two new oem sensors and still a misfire. now the only conclusion i could come to was pcm. so online i ordered one brand new. hooked it all up and start it up, still a misfire! i take it for a ride and it was misfiring sooooo bad, way worse than the original misfire. bring it down reset it and it was back to a cylinder 4 misfire, did a compression test and it checked out perfect. I am at a total loss. and my MPG's are 13 on the highway!
current codes: cylinder 4 misfire and coil D not reaching maximum dwell time
randomly the check engine light will go off but it still has the rough idle.
the only modification is K&N cold air intake.
I'm going to assume the codes go hand in hand with each other.
the only possibilities i can come up with:
grounds (free) not leaning towards this though.
however if one was bad i would think it would have a code for the faulty sensor. knowing now that jeeps like oem parts, the cost to replace all of this is $$$ and being a student im not sure if i want to risk it and it still misfire.
anyone who can contribute information besides "search" thank you in advance!