Misfire problem

[JoeUtley]

I am having problems with my 2005 Wrangler 4.0. I changed my spark plugs due to higher mileage and not knowing when the previous owner did the same.
First set was Champion Platinum Power (Single Plat)
Engine ran rough as hell. Assumed it was the type of plug so I bought another kind, after removing the plugs realized the gap was wrong on most.

Bought the Champion Copper plus, made sure the gap was right (.035)
Ran good as new for one day. Following day got the p0302 cylinder 2 misfire code.

After reading this thread. Bought the Champion Double Platinum.
Ran good as new again, after one day started running rough, next day the P0302 code came on again.

I am checking the codes with the 3x ignition turn to on trick. To clear codes before the last time I changed them. I pulled the negative batt terminal while changing the plugs.

Being that the same cylinder is misfiring, and the coil going bad for just one cylinder is hard due to being a coil rail. How can I rule out the injector for that cylinder?

Is the 2nd cylinder the 2nd from the front bumper?

Are there any other issues that could cause misfire?

 

[mots]

I hate to hijack this thread however I am having similar problems with my 2005 Wrangler 4.0. I changed my spark plugs due to higher mileage and not knowing when the previous owner did the same.
First set was Champion Platinum Power (Single Plat)
Engine ran rough as hell. Assumed it was the type of plug so I bought another kind, after removing the plugs realized the gap was wrong on most.

Bought the Champion Copper plus, made sure the gap was right (.035)
Ran good as new for one day. Following day got the p0302 cylinder 2 misfire code.

After reading this thread. Bought the Champion Double Platinum.
Ran good as new again, after one day started running rough, next day the P0302 code came on again.

I am checking the codes with the 3x ignition turn to on trick. To clear codes before the last time I changed them. I pulled the negative batt terminal while changing the plugs.

Being that the same cylinder is misfiring, and the coil going bad for just one cylinder is hard due to being a coil rail. How can I rule out the injector for that cylinder?

Is the 2nd cylinder the 2nd from the front bumper?

Are there any other issues that could cause misfire?

Yep, cylinder 2 is 2nd from the front bumper. If you don’t have any other PCM codes to go by besides just the misfire code for cylinder 2, I would likely swap out the #2 injector. If that doesn’t fix it, then a compression test could be in order. The single unit coil pack is servicing both cylinders 1 and 2, so that is not likely the problem if cylinder 1 is not giving you any issues. If you replace the injector, double check the plugs, gas is good, and compression is in spec, and there are no other codes, then you could be looking at a damaged valve (stuck shut if compression is good) perhaps, but that is not very likely unless you have very high mileage. Are you sure that is the only code you are getting?

 

[Jerry Bransford]

Could also be caused by a bad crankshaft position sensor. Swap the #2 injector with another cylinder & see if the problem follows the injector or stays at the #2 piston as I suspect it will. Swapping injectors is easy, there's nothing tricky about it other than make sure you don't booger up the injector o-rings and that you get them seated fully and correctly.

 

[JoeUtley]

Could also be caused by a bad crankshaft position sensor. Swap the #2 injector with another cylinder & see if the problem follows the injector or stays at the #2 piston as I suspect it will. Swapping injectors is easy, there's nothing tricky about it other than make sure you don't booger up the injector o-rings and that you get them seated fully and correctly.

I’ll swap the sensors and come back.

 

[JoeUtley]

I’ll swap the sensors and come back.

I swapped the fuel injectors and the code never came back. But I could tell I was still misfiring. I got a good coil rail off someone and installed that... Voila problem solved. Got the rail for free so ended up not so bad. Thanks for helping me out!