muddywagon

I have an 03 Grand Cherokee, 4.0L Engine. 98,000 kms (60,000 miles) One really cold night (-30 degrees celcius) I started it up and it was misfiring. It had always been plugged in and regular maintenance done.

Ran the code, it was P0303 - #3 Cylinder Misfire. I read every stinkin forum post I possibly could find on every jeep website, and started doing all the recommended ideas. I read all the TSB's on this issue too. Including a trip to the Dealer and tried all of their ideas.

They said the injector was faulty and to replace it. Also change the plugs to the original Champion plugs, because I had bosch platinums in it. I did and after this and everything else i've tried, They're completely stumped. They have had it in on two separate full days and are now calling their tech support because they have no idea how to fix it.

Here's whats been done:

New spark plugs (twice, with the bosch in you can actually drive it. With the champions it chugs so hard you have to pull over)

New Fuel Filter
New fuel injector on cyl. 3
New Oil/filter change
Sleeves on all six injectors
Thermostat recently changed
Rear main seal done 1 year ago
Coil Pack Rail looks good, boots and coils inside them look new
Fuel pump tested and checks out fine
Battery tested and checks out fine
Combustion cleaner through throttle body
Even tried the Seafoam treatment

So It seems like the third plug is getting lots of fuel. The electrode looks green like fuel and smells of gas. The other plugs are black and 5 & 6 are a bit oily. My senior ford tech friend says that with all of that done to it and judging by all the carbon coming out of the exhaust and and the putt-putt exhaust, that it is likely a burnt valve/ring. I have read the TSB's about the valve rotation and I am starting to believe that it needs a valve job.

The only thing is that it should be covered under the powertrain warranty and the Dealer won't fix it because they still don't think that is the problem. Warranty is almost up, and they refuse to open it and check the valves. They are supposed to talk to their tech support this week, and the jeep will go back in next wed. I even made the service advisor read the TSB's.

I'll pull the head off myself if I knew that was the problem. What do you guys figure? Has anyone resolved their misfire? So many of these with the same problem. I think it's time Chrysler made it a recall. Class action suit is needed!

thoughts?

skiebuster

Make him put it in writing that he doesnt think its the valves, and why he doesnt think its the valves, with current mileage and tell him if you find out its the valves after it rolls over and goes out of warranty, you will sue.

Be firm yet nice aboutit.

a messed up valve trick, take a dollar bill and hold it over the tailpipe. If it sucks it in, burnt valve, if it only pops it away from the tailpipe, good to go.

ckysodkorn_xj

they are suppose to check it anyway. it's under warrenty take it to the shop let them give you a rental and they fix it free. tell them not to give it back untill it's fixed but tell them you want it back within a week. if not you will bring a

04freedom

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf

edit: didnt see that you read all the tsb when i posted

muddywagon

The dealer won't check the valves. Thats just it. They don't think thats the problem. I have decided to replace the 02 sensor, just to prove them wrong, again. I am going there tomorrow to talk to the manager, and I'm going to call Chrysler.

By the way compression is 150,160,140,150,150,155. It's all within in the spec range, but the third is considerably lower. Could it still be a burnt valve?

sems

Tell them to do a Cylinder Leakage Test. I have seen similar results to your compression test before with it still being a burnt valve. If there is any valve/head damage, the cylinder leakage test will show it.

muddywagon

I am replacing the O2 sensor tomorrow, just to make sure thats not the problem. I will get the dealer to do the leakage test next.

muddywagon

Yeah, so I changed the O2 sensor today (the one the dealer said was faulty) and guess what happened. ABSOLUTELY NOTHING! I am getting pretty frustrated at this. Well at least I get to tell the dealer on monday that they were wrong, Again!

milmat1

COIL PACK !
Coils dont have to look bad to be bad ! With your #3 Plug staying wet it's a good indication it isnt firing. The supercold weather and a little condensation in the coilpack could have started this whole thing..
If it were me:

If would do a proper compression test and verify the cylinders are all sealing well and nothing has broken or burned. (especially on #3 !)
If you have the coilpacks like mine about all you can do is substitute a known good one for the test.
But the Spark Plugs tell the story ! Your #3 Cyl isn't firing or isn't getting up to temperature ! And the O2 sensor will not cause ONE plug to misfire !


FYI: http://www.gregsengine.com/compress.htm

milmat1

I just read in another thread where a guy found the wire for the number 3 cylinder had rubbed the valve cover until it was shorting out !!

His symptoms were nearly identical to yours !!...??

dirtmod0

I like this answer the best!! I have worked for dealerships and if we didnt find it go further, the dealership gets there money regardless.
It sounds like a valve issue, i would do a leak down test after the thrid or fourth step,to me its just common sense the engine needs just the basic if it has that then go further.i would almost bet money on a valve problem

muddywagon

Thanks for the info Milmat. I am going to have them test the coil pack tomorrow as well as have the leakage test done. Hopefully something comes of it. I was thinking about pulling a coil pack outta the junk yard and swapping it out. If that does the trick i'll go buy a brand new one. It was last on my list since theyre over $200. I knew the O2 sensor wouldn't do anything, I just wanted to prove the dealer wrong.

Now about that coilpak rail, its one rail with three paks on it. Wouldn't two cylinders be down if it was faulty. Dont they each run two cyls? Or is it possible to have just one down?

thanks again

muddywagon

Oh by the way,

I pulled the whole coil rail off the other day and stuck the third plug into it loose. Had the wife turn it over while I watched and what happened was the #4 boot sparked pretty good (without a plug in it) The third didnt spark at all. #1 and #2 hardly had any spark, so Im starting to think it is the rail that is faulty.

dirtmod0

yep think you have it, I should have read ur list a little better. you should have spark out of each

rwlkr

sorry.. I know this thread is a year old, but I am having the same problem on my 2003 Laredo 6 cyl. Muddywagon, I'm assuming you replaced the coil packs and that resolved the issue? If not, how did you resolve the issue (assuming you resolved it by now).

I replaced the coil packs, the plugs and the computer and am still having a misfire on cylinder 1. I just replaced the computer about an hour ago, and it idled perfectly for about 5 minutes. Just as I was about to take it for a test drive, the check engine light came on and it started running VERY rough and I smelled raw fuel. Checked under the hood and no fuel leaks.

this all started about a week ago. My wife was on her way home from work and she said the thing started to hesitate and she smelled gas. I took it to a mechanic friend and he hooked up his scan tool and said that there seemed to be a problem with the injector driver on cylinder 1, thus my replacing the computer. He said that he thinks the injector is basically wide open and just dumping fuel into the cylinder. But, as stated, I replaced the computer and the problem came back. Just kind of weird that it idled like it was brand new for about 5 minutes.

This is getting pretty expensive and annoying! Please post your results muddywagon. I'd REALLY appreciate it!