Cylinder 3 misfire and P0303 code

I found this info: Check for a wiring rub through to the number three injector at the bracket for the throttle cable, if the injector connector is not turned towards the rear of the motor (2 o'clock position) and is facing up the wiring can chafe on this bracket causing the injector to not spray fuel at times or constantly.

I moved all mine back to basically 12 o’clock and number 3 to 2 o’clock.
 
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I wrapped injector 3 with the recommended insulation, and replaced the exhaust manifold insulation with a new one. Drove home from work on 80 plus degree day. Parked in the driveway, went back 10 minutes later to start it and it idled rough for a few then smoothed out. Does not look like the insulation cured my issue. Any other suggestions?

CEL and code P0456 (Evap Leak) reared it’s ugly head while driving home, but Jeep ran fine all the way home.
 
Mikester86 said:
I wrapped injector 3 with the recommended insulation, and replaced the exhaust manifold insulation with a new one. Drove home from work on 80 plus degree day. Parked in the driveway, went back 10 minutes later to start it and it idled rough for a few then smoothed out. Does not look like the insulation cured my issue. Any other suggestions?

CEL and code P0456 (Evap Leak) reared it’s ugly head while driving home, but Jeep ran fine all the way home.
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It sounds like your #3 injector may not be working properly, or perhaps it is still not shielded properly. If it is the injector, I would guess the injector is not mechanically not working (delivering enough fuel). If it were electrically failing, or the connector was corroded and causing a bad or intermittent electrical connection to the PCM, I would think another OBDII code would be thrown for the injector circuit. Instead, you are just getting the misfire code reported. At least you are dealing with one cylinder, so that narrows it down.

If you swap the injector with another cylinder and the problem follows, it is your injector. I’d double check the insulation first though.

At worse case, cylinder 3 could have low compression and causing the misfire, but I’d rule out the easy stuff first.

Not likely a coil pack issue since it would affect two cylinders as we said before.

Your evap code could be just a leaking gas cap, or perhaps it is something else leaking in the evap system. Not likely the culprit of the misfire though.
 
My cylinder 3 misfire was due to the ignition coil. Easy fix. I had already changed plugs and bank 1 sensor 1 O2 (earlier code for he sensor, before the p0303 code).
 
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Jerry Bransford said:
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
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Amazon said that wouldn’t fit my 2002 4.0L TJ, but this set of 6 would https://www.amazon.com/dp/B072HGFZ6W/?tag=wranglerorg-20
 
My 2006 4.0 engine is up to the cylinder #3 misfire again now that the weather is warmer. 2006 should have had the shielding from the TSB from the factory right? In past years it has been specific as in if I left a hot engine for about 5 minutes it would misfire. If it was much shorter or longer than 5 minutes it would be fine. This spring it seems to have gotten worse. I get the #3 misfire after fueling up or after a 20-25 minute shutdown, that has never happened before. Are there any other solutions?
 
Viking Jeeper said:
My 2006 4.0 engine is up to the cylinder #3 misfire again now that the weather is warmer. 2006 should have had the shielding from the TSB from the factory right? In past years it has been specific as in if I left a hot engine for about 5 minutes it would misfire. If it was much shorter or longer than 5 minutes it would be fine. This spring it seems to have gotten worse. I get the #3 misfire after fueling up or after a 20-25 minute shutdown, that has never happened before. Are there any other solutions?
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If your '06 doesn't have the #3 injector wrapped with insulation it makes good sense that doing so would cure that #3 heat soak issue. Just buy the below insulation Jeep specified for that fix and zip tie it into place around the #3 injector and my bet is it'll be cured. https://www.amazon.com/gp/product/B007O3QHDK/?tag=wranglerorg-20

This is my #3 injector and I have no heat soak or misfires.
Fuel Injector Insulation .jpg
 
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It looks to me that the later models had more insulation on each injector. This certainly looks thicker than what I have seen in pics of earlier models. I dont think those insulators will go over what I have.

I did find the wiring connection twisted almost to the 3-4 o clock position and pretty much touching the heat shield. I wonder if that was the problem. I rotated up to 1-2 o'clock like recommended.
IMG_9066.JPG


IMG_9066.JPG
 
Jerry Bransford said:
Then continue making more posts asking what to do about your #3 misfire and don't try the suggested $10 fix that takes less than a minute to install.
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@Viking Jeeper my absolute major heartfelt apologies you were correct to :ROFLMAO: at my above previous suggestion, how could I have ever been so stupid as to have suggested to you that $10 one minute job might be the fix for your #3 misfire.
 
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Picked up a 2002 TJ over the weekend with 73K miles on it. The previous owner let the Jeep sit for quite a while and replaced the battery the same day that I purchased it. I went to have the required TX emissions test done today and the Jeep failed due to not being able to communicate with the test equipment. I was told to drive it 60 plus miles or so due to the Jeep having sat and the battery replaced. Put on 65 miles and it failed again for the same reason. However, when I started the engine after having sat for 15 to 20 minutes I could feel a misfire that cleared up after a few minutes of driving. Pulled out a code reader which showed no codes, but I did find a pending code for #3 cylinder misfire.

So thank you for your all the information I found and read here, parts are ordered via Amazon. Videos are an extreme helpful tool. Hope to get this misfire taken care of soon.

Now if I could figure out this dag-gum failure to communicate issue!
 
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