I have a 2002 straight 6 TJ. Been driving it about 200 miles each weekend from Nash to Knox. Recently, started it up and it idled rough then check engine light flashed. Code was p0303. 3rd cylinder problem, first thing I did was replace the spark plug and I am getting the same code. Heard I should replace the coil and maybe check the fuel injector, any other solutions or similar problems?
Cylinder 3 misfire and P0303 code
- Thread starter Zachhorn47
- Start date
If you have coil packs you could pull the #3 coil pack and try switching it with another like #1 and if it brings up a code for #1 the it would be the coil pack. This might help narrow it down more for you.
I have a thread on how to troubleshoot a misfire code — https://wranglertjforum.com/threads...the-dreaded-misfire-and-how-i-solved-it.4212/
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Don't know that I agree with that. The 4.0 uses a waste spark coil system, meaning that one coil fires 2 cylinders at the same time (one is wasted). If it had a bad coil you would also get a code for the other cylinder being fired by that coil.
The only part of the coil that could be bad for only a 1 cylinder code would be the plug boot.
Yeah, I knew that each coil fired 2 cylinders, I just figured if you swapped one out for the other, you'd get a different set of check engine codes.
Anyways, I may very well be wrong.
I know there is a TSB regarding this error code as well, and I believe the fix was to put heat shied around the number 3 fuel injector.
@Ian was having the same issue in his thread here:
New from North Dakota: P0303 code and cylinder 3 misfire
C.J. Roberts
TJ Addict
Misfire on number 3 cylinder is almost a heat soak issue. Sparkplug wire insulation over the injector is the factory solution.
Yeah, there is a TSB out there from Jeep about this, can’t remember what number the TSB is, but I’ve seen it before.
Yep, that misfire is most likely from the fuel vaporizing inside the #3 injector caused by heat from the exhaust header collecting in that area. The fix for that is to wrap a piece of insulation around the #3 injector and zip tie it into place which fixed my #3 misfire.
This is the product called for in the Mopar TSB that fixes that problem... https://www.amazon.com/gp/product/B007O3QHDK/?tag=wranglerorg-20
This is the product called for in the Mopar TSB that fixes that problem... https://www.amazon.com/gp/product/B007O3QHDK/?tag=wranglerorg-20
I linked the TSB in my misfire troubleshooting thread — https://wranglertjforum.com/threads...the-dreaded-misfire-and-how-i-solved-it.4212/
Ian
Member
Do what they have said first, but that wasn't my issue. My head needed to be rebuilt. The sleeves on multiple valves were junk. What they're suggesting is a lot cheaper and easier, and could be the only problem. If that doesn't fix it, bring it to a mechanic to do a compression test and leak down test. My thread that chris linked has some good information if it gets that far.
Can someone post a photo of how this shield gets installed, please? I really don't see how I'm supposed to put it on there. Trying to avoid taking it to the dealership. Thanks so much.
C.J. Roberts
TJ Addict
Just ordered this insulation due to the exact issue happening to us recently. This forum saves the day again!
Dumb question, how are they numbered? Is it injectors 1-6 starting with injector number 1 engine front?
One more question; the service bulletin states to place the injector at the 2 o’clock position from driver’s side. Should all of the injectors be placed at the 2 o’clock position?
I read that too in the bulletin and found it interesting. Honestly, I would not touch the other injectors, I would just insulate #3 and adjust as they point out to shield from the heat. I'd have to double check, but I believe only #3 on my 2005 is oriented differently (assuming they did this at the factory, but who knows!)
All of my injectors were facing more like 10 o’clock from the driver’s side. I did adjust them all to the 2 o’clock position, which would be 4 hour positions clockwise. Does anyone know their proper orientation?