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View Full Version : New to this, CYLINDER 3 MISFIRE. HELP!


88XJowner
December 20th, 2009, 17:07
Hello, I recently bought a 1997 cherokee sport and the guy did an AX-15 conversion (from auto), He changed out the motor, trans and transfer case. And It was running/driving fine until about a week ago. It has all the codes it should for being swapped... P1899, P0743 and P0753 etc.

So last week I was driving it and noticed it was sputtering upon start off.
Read the codes again it was P0203 (cylinder 3 fuel injector circuit malf.) Checked the wires and what not then replaced the injector and it was fine for a day.

Now this got worse, it began misfiring P0303 and P0203 are now being stored. P0303 is a cyl. 3 misfire. So I finally brought it to a shop and four days later the guy told me to get a manual trans PCM and replace the DS O2 sensor. Okay did that and again it ran fine for a day and now it's running worse than ever the exhaust smells like fuel and it's barely drivable. And the cyl. 3 spark plug is soaked in gas and charred.

I love this jeep but I'm getting very close to junking it. I'm driving it around right now with the 3rd injector unplugged. Sounds like an STI LMFAO.

Please help!!!

birchlakeXJ
December 21st, 2009, 05:44
Before you do anything else, check compression. You may have a problem internal to the engine.

If compression checks out, you have to concentrate on things relating specifically to that cylinder. Have you actually changed the #3 plug? Changed the plug wire? Verified the injector is firing with a noid light? Changed distributor cap/rotor?

RNMedic
December 21st, 2009, 16:09
or head gasket. get it Hydrocarbons sniffed

StealthXJ
December 21st, 2009, 17:08
Not sure how far back it goes, however there is a TSB for the #3 cylinder misfire for the later (at least the '01) XJ's.
Might be worth checking into and see if it includes your year.



:)
Fred

JJacobs
December 21st, 2009, 18:39
Hang on. A 203 can cause a 303. A 303 cannot cause a 203. Find the problem in the circuit whether it's injector, wiring, or pcm.

88XJowner
December 21st, 2009, 18:57
Not sure what a TSB is. And yes I've replaced all the simple stuff already. Spark plug, wires, injector, upstream O2 and still upon pulling out the spark plug it's soaked in gas. So the injector is firing.

A reliable source told me these 4.0's have issues with premature wear of the camshaft lobes and that it could be throwing off the timing (for that specific cylinder) causing fuel to be unburnt during the combustion stroke and fouling plugs and O2 sensors thus causing an over rich misfire. (meanwhile seeming like there's an electrical issue from the inejctor to the PCM.)

This is probably the worst issue I've had with any of the 23 vehicles I ever owned. And I've had some pieces of sh*t before!

StealthXJ
December 21st, 2009, 20:09
Not sure what a TSB is. And yes I've replaced all the simple stuff already. Spark plug, wires, injector, upstream O2 and still upon pulling out the spark plug it's soaked in gas. So the injector is firing.

A reliable source told me these 4.0's have issues with premature wear of the camshaft lobes and that it could be throwing off the timing (for that specific cylinder) causing fuel to be unburnt during the combustion stroke and fouling plugs and O2 sensors thus causing an over rich misfire. (meanwhile seeming like there's an electrical issue from the inejctor to the PCM.)

This is probably the worst issue I've had with any of the 23 vehicles I ever owned. And I've had some pieces of sh*t before!

A TSB is a Technical Service Bulletin, in this case issured by Chrysler.
I know that, at least, the 2001 (I have an '01) has a TSB issued for the #3 misfire code/problem. The problem is that the injector for the #3 cylinder gets hot and this creates vapor lock. The TSB describes how to insulate the #3 injector from the heat generated by the exhaust manifold in that area.



Fred

88XJowner
December 21st, 2009, 20:33
The TSB wasn't much help. It's not very free either.

StealthXJ
December 21st, 2009, 21:16
The TSB wasn't much help. It's not very free either.

Never said it was free..
Also said that I didn't know if it applied to your model year.


:)
Fred

88XJowner
December 21st, 2009, 21:44
So the best part of my day never could've come later! I fixed the b*stard!!!
I spoke to a guy that works next door to me at a shop and he mentioned something about the harness running behind the valve cover possibly rubbing through the insulation on a wire and BAM! that was the problem. So if you get an isolated misfire check that first! Check the link below.


http://www.facebook.com/photo.php?pid=141126&id=1734110915

birchlakeXJ
December 22nd, 2009, 05:57
The link just brings us to Facebook login so won't get us the info.

Can you elaborate on exactly what wire was damaged?

88XJowner
December 22nd, 2009, 14:42
The wiring harness that runs behind the valve cover had been rubbed through by the head bolt on the corner. And it only damaged the white/yellow wire for the cylinder three fuel injector, causing a ground. Try again, got a photobucket account now.

http://s904.photobucket.com/albums/ac243/96hurricane/Vehicles%20and%20toys/?action=view&current=misfiresolved.jpg

birchlakeXJ
December 22nd, 2009, 16:30
Good find on that facebook guy that led you in the right direction. A noid light would have showed that injector not firing but with his tip, you didn't even need to do that.

Thanks for posting the pic. Always interesting to hear the resolve.

JJacobs
December 22nd, 2009, 17:33
The facebook guy? I think I posted his answer in this thread. :) Not specifically where to look, but still.

birchlakeXJ
December 22nd, 2009, 17:36
The facebook guy? I think I posted his answer in this thread. :) Not specifically where to look, but still.

I apologize and stand corrected JJacobs. You definitely get the cookie too! :yelclap:
Very nice work on this one. These type of problems can really get your goat. Wiring is oftentimes overlooked.

I like it when I learn stuff.

JJacobs
December 22nd, 2009, 18:20
I just like that the guy was ready to cut the Jeep up and throw it in the dumpster by the sounds of things, and now it's happy. Maybe he'll see the light on xj's now. ;)

88XJowner
December 22nd, 2009, 23:17
I was pretty close to arson with the thing but it all worked out for the better. And the guy that pointed me in the right direction owns the shop next door to mine he wasn't on facebook, unless I missed something? LOL

Just another happy jeep and happy jeep owner!!!:party: