OAS

2002 Grand Cherokee Limited 4.7 V8 120,000 miles.

Wife told me "Took the dogs out for a hike, Jeep ran fine. Got in to go home, barley idles, runs very rough."

Did the "turn the key 3 times" and got 3 codes.
P0300 , P0307 , and P0308.

Cylinder misfires acording to Quadratec's website.

https://www.quadratec.com/jeep_knowl...article-39.htm

I'm thinking coil packs/ plugs? Maybe Fuel injectors?

This thing was babied by the former owner and is CLEAN.

Any ideas are appreciated.

Thank you!

BlueRidgeMark

Check your cables and grounds first, not because it's the most likely problem but because it's free and cheap and might be your problem.

Hard to believe a coil pack going south all at once like that. Verify fuel pressure.

97grand4.0

You are thinking right, cyls 7 and 8 coil pack. Classic codes for this. 300 is the general misfire, and cyls 7 and 8 are misfiring.
if unsure, replace with a junkyard $10 pack(s). Just went through the same scenario twice with 2 relatives cars.

OAS

Well, to update. I replaced all 8 coils and all 8 sparkplugs. The old ones were getting pretty bad. And figured why just do 2 coilpacs. Also replaced the PCV valve and the TPS sensor since i read its a good thing to do.
Same problem!
Its also throwing another code now , P0207. ???
Check grounds, seemed clean.
UGH!

97grand4.0

As you probably know already the PO207 is for the injector cylinder 7. It could also be the wiring harness or the pcm.