Misfire Issue--HELP!

[Phil + Neela]

Hello all,
I have a '08 Jeep Liberty Sport and have been having trouble with it for about a month now.

It all started one morning when I hopped in after working out. I started her up, drove about 100 feet, and got a flashing CEL. I immediately pulled over and shut her down. Upon restarting, I had a solid CEL and no other issues.

The next morning when trying to leave the house, I got the same flashing CEL and a very obvious misfire vibration. I shut her down, and upon restarting there were no issues.

Later that day I went to Autozone who pulled the p0300 Multiple Cylinder Misfire code. I put some injector cleaner in there and got some reputable gas to solve any clog/bad fuel problems.

No misfires for two days, then it started misfiring to the point where I had to restart it twice to get the misfiring to go away. Still only gives the p0300 code.

I changed the plugs, which unfortunately had ZERO effect on the misfiring issue.

I finally broke down and turned it into the dealer. They were completely stumped becasue they could only get the p0300 code as well, so they were at a loss as what needed fixing. After flushing the fuel rail (and keeping it for 7 days) they said it was fixed.

They also reflashed the PCM, which was a nice bonus. It definately drive and shifts nicer than it ever did before

The dealer fix lasted for 24 hours, then the misfires started just as they had before--possibly even worse.

Today after some more research I cleaned the MAF, but that didn't fix anything either.

I'm totally at a loss right now and will be bringing it back to the dealer soon.

Does anyone else have any ideas? I would prefer to have a vehicle instead of leaving my Jeep at the Black-hole-that-is-the-dealership for another week or two.

 

[Snail Farmer]

Replace the O2 sensors with NTK. That's what finally fixed mine when I had that problem.

 

[Phil + Neela]

Replace the O2 sensors with NTK. That's what finally fixed mine when I had that problem.

I remember reading in one of your posts that your replaced both (?) of them. I think you said something about a special tool to get them out as well? I could be mistakin, as I read a lot of posts before putting my story up.

 

[Snail Farmer]

I replaced all 4 on mine. You only need to replace the 2 upstream (pre-cat) sensors to eliminate any problems though. They make a special socket for O2 sensors that has a slot in it. It's only a couple bucks to buy. I had one laying around, but you don't need it. An open ended wrench will work also.

 

[Phil + Neela]

Well, hopefully this saga has now come to a close. The dealer (at my prompting and after a callback to the manufacturer) replaced the two upstream O2 sensors (just as Snail Farmer said) and I haven't had any problems in about a week. It did take them two whole weeks to "figure" everything out--I'm just glad everything got done

 

[rockymountain]

Awesome! I almost welcome my dash lighting up now with a p0300! Bring it on!!!!

 

[Phil + Neela]

Time to close this one out! No problems since the dealer replaced the upstream O2 sensors! And in a great customer service move, they didn't charge me for the second "fix" becasue they didn't get it right the first time. That's professionalism right there!

 

[sevenhelmet]

Good outcome. Nice to see a dealer that doesn't charge you for all they can. I will file this one away in my bag o' tricks.