My 1995 YJ misfire issue

Rio95

New Member
Joined
Mar 11, 2023
Messages
4
Location
Nantucket, MA
Hello,

I’m new to the forum, my name is Nick. thanks for the add!

Looking for help. I am pulling my hair out…
I have a 1995 YJ 4cyl w about 100k on it.
Recently it started misfiring when at idle, and under load. I got a check engine light and the code I got was TPS sensor. Replaced that and the code went away. But the misfire stayed…

I have replaced all the following and it is still misfiring..

Spark plugs and wires
New distributor
Ignition coil
Fuel filter
Fuel rail and fuel injectors
Tested injector wires with noid light
New MAP sensor
Throttle position sensor
Idle air control
Crankshaft position sensor
Air charge sensor
Coolant temp sensor
Checked valve springs
New valve cover seal
Changed battery ground cable
Ground to fuel injector
Fuel pressure good
Compression good
No head gasket leak
Pigtail for distributor connection
Pigtail for injector 3
Checked grounds and used grinder to expose metal


Note- after changing the valve cover seal (checked valve springs) the misfire was gone but only for about two hours… hasn’t gone away since. I assumed I moved a wire so I’ve been chasing the electric gremlin the last few weeks…

I have had numerous mechanics try to diagnose the issue, no luck…

Anyone have advice for me? Or anyone recommend a Jeep specialist near cape cod, MA? I’m on Nantucket.

Best,
Nick

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You may have a worn cylinder. Check the compression on each cylinder. Harbor freight has two test kits. I found the slightly more expensive one to work better. Depending on the severity of the results you may be in for a rebuild…or if it is minor try using a quart of Lucas high mileage oil stabilizer with each oil change. My 2.5 has slightly low compression in one of the cylinders and it loves when I put this Lucas engine “honey/molasses” in it.

Dang, just re-read your post and it stated you checked compression…now my only suggestion is marvel mystery oil…kidding. How about clogged catalytic converter, vacuum leaks, cracked manifold.
 
Thanks so much for the reply. We tested compression and it was good. But, at this point it wouldn’t hurt to test again..and thanks for the oil tip!


Nick
 
A recent post if I remember correctly, had found a plug in connector under the hood that was worn and not keeping continuous contact. I believe that it was also causing an ignition problem. These can be a royal pain for sure.
 
A recent post if I remember correctly, had found a plug in connector under the hood that was worn and not keeping continuous contact. I believe that it was also causing an ignition problem. These can be a royal pain for sure.
I thought I had found the issue… the Jeep wouldn’t turn off after fumbled around w some wires so I bought a new connector for the wire harness side of the dist. Now it turns off but still misfires… when the weather clears up I’m gonna check the connector to the throttle sensor again … that was the original code I got.
 
I thought I had found the issue… the Jeep wouldn’t turn off after fumbled around w some wires so I bought a new connector for the wire harness side of the dist. Now it turns off but still misfires… when the weather clears up I’m gonna check the connector to the throttle sensor again … that was the original code I got
Thanks so much for the reply. We tested compression and it was good. But, at this point it wouldn’t hurt to test again..and thanks for the oil tip!


Nick
You may have a worn cylinder. Check the compression on each cylinder. Harbor freight has two test kits. I found the slightly more expensive one to work better. Depending on the severity of the results you may be in for a rebuild…or if it is minor try using a quart of Lucas high mileage oil stabilizer with each oil change. My 2.5 has slightly low compression in one of the cylinders and it loves when I put this Lucas engine “honey/molasses” in it.

Dang, just re-read your post and it stated you checked compression…now my only suggestion is marvel mystery oil…kidding. How about clogged catalytic converter, vacuum leaks, cracked manifold.
I have thought maybe clogged cat… I plan to do the exhaust at some point but it is decent shape. Guess I should do it sooner than later
 
OK....Get into a garage or an encloser that can do total darkness....Fire it up with the hood open and look for any arcs...
I have found dozens of misfires that way.....