I got 1998 with some heat soak problems but thing is its happening while it's running. It does get worse if I stop it and let it heat up then start it again
The misfires happen as soon as i get past 210 degrees.
and they don't get better if I Rev it. The only time it gets better is when it cools down.
I know people have this after turning on and off but this just happened today while sitting at a drive through while running. Just randomly starting acting up. It doesn't clear up by reving it only clears up with colder Temps.


I'm trying to narrow my options since it happens while running.
If it does it while running does that mean it has nothing to do with the injectors? I've juggled the wires and noticed no differences in case I had a lose wire.
I have notice a very weird thing where my tach bounces if that helps but the jeep idled fine before
I've changed the thermostat sensor
Plug wires
Spark plugs (autolite coppers)
Ignition coil from standard ignition (oriellys)
MAP sensor
TPS
the only things I havnt done/changed are injectors, distributor cap, and done a compression test.

I just find it odd after 210 degrees it decides to act up with no CEL.

 

sounds like the issue arises when you switch to open loop. check your O2 sensor wiring. I'm not 100% but if you unplug your O2 it will go back into closed loop mode. If it runs right then it's your O2 sensor. Search open loop vs closed loop for more info. someone more advanced will chime in shortly.

 

@psf4x4 I'll try that today after work! I've never heard of open loop and closed loops before so this should be interesting. I'm going to check fuel pressure and other things today aswell. I just don't want tp spend 100s of dollars hunting.

 

You should concentrate on the up stream O2 sensor(s). Depending on your model and emissions you may have anywhere from 2 to 1 upstream O2 sensor.

 

Closed loop happens well before normal operating temp. I don't remember the temp, but it's not at 210F.

Clean your grounds, check the distributor cap and rotor, and take a close look at the old spark plugs. If one or more was oil soaked, that could be an indication of something bad happening with the base engine.

Another quick/easy check to do is to keep a squirter bottle of water in the car with you. When it starts acting out, spray the CKP sensor (behind the head on the driver's side in the transmission bellhousing). Sometimes cooling them off makes things better. So if it starts getting better when you cool the CKP sensor, you know what your problem is.

 

I stated closed loop and open loop incorrectly. The vehicle operates in open loop where it ignores several sensors until certain conditions are met (temp is one) and then switches to closed loop where it runs based on sensor input, in short.

agreen, I assumed his dash gauge was not accurate like most of them.

 

@agreen alright awesome I'll go ahead and check those. I replaced the crank position sensor about 2 years ago but with a oriellys branded one. Never had issues I guess till now if that's what it is. I hope it's not oil soaked spark plug.
When i do check the cap and rotor what do i look for? I remember seeing something saying make sure it doesn't wiggle. Besides that that's all I know for cap and rotor.
spark plugs I got about 3 months ago. I'll still dig into all of them and see if I can catch the problem.
@psf4x4 I'll check the loops and if they're acting up. I'm borrowing a coworkers digital obd2 scanner.
I'll have to look up the parameters for the injectors and timing and etc. Anything I should look out for while I'm looking at things digitally?

 

A bad cap will have corroded contacts. You should change it and the rotor when you replace the spark plugs.

 

@agreen figured it out!
so I did all the checks with rotor, cap and spark plugs and checked all fluids!

It was my ignition coil. I bought one a couple weeks ago from oriellys called blue streak I think and it worked great for the time being! But i had my old one that i changed out even though it was good I changed it but kept it knowing it was okay and swapped over. Now it runs great through all Temps!
I suffocated the grill to simulate it heating up and all through the numbers from cold to 221 when the Gans kick in no back fires!
I did however replace the cap and rotor because it did look like your photo but that was after finding the problem ignition coil!

I appreciate your guys help!

 

I'm hesitant to believe the coil was the culprit. I've used a lot of Standard Ignition stuff, and for the most part they've been good to me. I currently have a blue streak coil on my XJ. There are some ground wires right there by that coil. It could be the coil, but I just don't think it's too likely.

But, I'm glad it works for you!

 

@agreen This weekend I'll try to get to all the grounds and clean them all. You happen to have any photos on hand of where all the ground points might be? If not I'll dig through Google. Yeah I was hesitant aswell thinking "no way"
but after I swapped them it ran fine. I also did the water bottle and sprayer trick and it seemed to have help when I'd spray it.
I'll keep an eye out on it though through the Temps. I still havnt checked compression though.
if the ignition coil failed would there have been a code for that?

 

The ignition coil is honestly just 2 coils of wire. There are a couple modes of failure for an ignition coil. One is that it shorts, and the vehicle won't run. One is that it goes open... and it won't run. The other way I know is that the plastic cracks and it still runs, but needs to be changed asap. I've never seen a coil with a partial or intermittent failure. Not unless it has a static exciter built into it, which these don't.

Those ground wires are RIGHT there on the coil bracket. You have to remove 4 of them I believe. They're behind the 2 bolts that hold the coil bracket to the engine. There are lots of writeups and even YouTube videos about cleaning grounds on the XJ.

 

Okay I know which wires your talking about. When i did happen to remove them i did scuff them a little. Who know maybe those couldve been my problem. Im driving it around right now and everything seems to be good for now! (Knock on wood)
I'm letting it heat soak on purpose to and everything seems to he holding. Even covering the vents to simulate it not getting fresh air.
To be honest I've had bad luck with parts and I'm slowly starting to think that getting Mopar made products might break my bank but woubut be lasting. I had a water pump die in another and half and a radiator in a year and couple months and I always buy orielly cause I've had worse luck with autozone.