Yes .035 is the correct gap for a I6 4.0.

It's probably just loose and needs to be tightened again. Seen that happen on other vehicles before. Happened to me on my T-Bird, installed new plugs and didn't use a torque wrench on them. Wasn't 20 miles later I had misfire codes on it from 2 loose plugs.

Would pull them and make sure it's not cracked or anything, reinstall and go from there.

from firewall to front of engine

6...5...4...3...2...1

so it would be one of the ones you couldn't get a torque wrench on.

The 4.0L firing order is 1 - 5 - 3 - 6 - 2 - 4

 

Or the boot is shorting out, that happened to me as well. Its a 6 buck part at AA, if the plug isnt the problem try that.

 

I would try swapping the coil pack and/or boot with another to see if that fixes it (or if the misfire code moves to the cylinder you swapped with) Hopefully that does the trick. If not, then swap the injector with another cylinder and check the code again. Still not fixed? Time for a compression test. 4.0s crack pistons with a higher frequency than most Jeep fans will admit.

A friend of mine started with the very same P0305 code and wound up needing a new 4.0 due to cam and lifter wear. He was running low-zinc oils, wheeling it all the time, and changing oil every 3000 miles. Well when all you do is wheel a rig, those are the hardest 3000 miles you can accumulate. Thankfully he had an 04 TJ Rubi and got his new motor barely within the 7 year/70000 mile Powertrain warranty.

Best of luck to you!

 

Thanks for the advice guys. The code actually went away last night. I'm thinking I'm going to pull out the plug and give it a look over and try my hardest to get a torque wrench on that one. I think I could get it with a u-joint.

 

So I took off the ignition coil and something fell to the ground, and I have no idea where it came from or what it is. Here's a picture of it. It feels like aluminum and its just a hollow cylinder with no threads.

 

thats just the spacer for the coil packs has nuthing to do with the actual firing. how did all the rubber boots look

 

Ok thanks, I didn't think it had much to do with anything. Should I put it back? If so, where does it go exactly?

The boots looked good, I glanced up each one of them and they looked clean. I took out the 5th plug and checked the gap, it was fine. I tightened it back down to what I think is good and tight, I wish I could get my torque wrench on there though.

For now the CEL is off and no error is being reported.

 

Clyinder misfires are happening again. This time it happend coming up the Cuesta grade on highway 101, doing around 70 with revs at 3200. When I reached the top I noticed my CEL was on, so I pulled off to check the codes. My odometer reported a P 0300, P 0302, and P 0305. Drove fine the rest of the way back to Bakersfield (about 120 miles).

So I'm guessing the next thing to check out is the coil rail assembly, right?

 

My money is on the fuel pump.

 

What would make you say it's the fuel pump?

 

Each firing needs spark, fuel, and air. Usually, when you get the random misfire (P0300), there is something wrong with the same component on all cylinders. That rules out individual plugs, injectors, and singular coils per cylinder if that configuration applies. Could be spark related to the coil. However, I believe that at the age of your vehicle it is much more likely that the fuel pump is starting to go bad. That would give you low fuel pressure as the pump dies. If you cannot get adequate fuel to the cylinders, particularly under hard load, then you will get random misfires.

Do you notice knocking going up hill under full throttle? If so, does going to higher octane fuel help? I had this exact same issue on my 4.0L ZJ, and it was surely the fuel pump.

If it were me, I would test the pressure at the fuel rail. It is really the fuel pressure at the rail under heavy load which will best show the issue if it is the fuel pump. However, that is not easy to measure. I have Scan Gauge II that will give me fuel pressure as I drive. You should still see a reduced rail pressure at idle with a pump that is going bad.

 

Thanks for the reasoning, that makes a lot of sense.

I didn't notice it knocking while going up the hill though. Everything seemed to be running fine.

Not sure if this also helps to know, but the CEL flashed at me for a bit, then went solid.

I'll have to get my fuel pressure tested. Thanks for the info kentman.

Also, the CEL is now currently off.

 

the aluminum piece is a spacer that goes into the plastic hose holder on the bolt on valve cover. Had the same thing happen to me.

 

Not the most technical guy here, but I cleared my P0305 with 2 runs of fuel injector cleaner. Intermittent code return after first bottle so I ran a second bottle of the Lucas brand thru. Code hasn't returned in 2 months now.
Not a sexy answer but it worked for my 4.7 99.