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hockeysack96 04-05-2013 05:42 PM

2006 Jeep Grand Cherokee rough running, engine code p0308
I am new to the forums & this is my first post.

My 2006 Jeep Grand Cherokee just started running rough out(like a misfire) of the blue. Idle slows down to about 500 rpm & sometimes will stall. When I step on the gas pedal & leave it running while in park at about 1500 rpm it seems to run fine, but as soon as I put in drive the motor runs like it is misfiring. Could some one please help me out with this? I can pretty much fix anything, but when it comes to diagnosing problems I am almost completely lost. I put a computer on it & got (2) code, the first code was p0308 & the second code was p0300. The codes describe possible fixes, but there are quite a few.

jedings 04-05-2013 06:39 PM

I had this exact problem with the same two codes about a month ago and it was saying cylinder 8 misfire and something to do with cylinder 8 injector. Of course I assumed thwle worse bexlcause that is usually how my luck goes. After looking around for awhile I realized I had a cut wire (maybe a mouse?) Going to the cylinder 8 fuel injector. The connection can also be corroded so start by popping the hood and looking all the way to the back of the engine on the passenger side to see if the wires are intact and if they are try unplugging the connector and plugging it back in.

jedings 04-05-2013 06:40 PM

Sorry about the typos... I am using my phone and didn't see them in time.

hockeysack96 04-21-2013 04:59 PM

Update to my problem. I failed to mention in my original post that about a week or 2 before I started having this problem I was sitting in a friends driveway & my jeep started to overheat. Turned the vehicle off immediately. Sat for about 45 min. talking with my friend then, left & drove home about 30 miles. No signs of overheating again. Ran good for the next 1 - 1 1/5 weeks. Anyways. I swapped the ignition coil from cyl. #8 with cyl. #3 & still the same problem. I bought this jeep with 31,000 miles on it & I know have 118,000 miles on it. I never have changed the plugs since I bought it. So I figured that I would change all the plugs, maybe the #8 cyl. plug was bad. Still same problem. While jeep was running started pulling each ignition coil plug to see if there was a difference in the motor sound. Motor sound changed on all except cyl. #8. So I decided to do a compression test. Cyl. #'s 1, 2, 3, 4, 5 & 7 ranged between 150-152. Cyl. #'s 6 & 8 were at 120. Right now I am in the process of removing everything to be able to remove the heads. I plan on taking the heads in to check for warpage & to have a valve job done on both heads. Right now I am at the point where I need to remove the fuel line from the fuel rail. The service manual states that I need a Snap-On tool #FIH-9055-1 or equivalent. Can I get this at Autozone, Advanced Auto Parts or Oreilly's? Any tips or videos anyone can point out to me?


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