Intermittent Misfire problem
 

SO I'm starting to get an intermittent missfire problem with my 95 xj 4L

Anyone know what the likely cause is? It will come and cause rough idle and stutter while driving. Then it will go away and reappear sometime latter.

I recently had all the plugs out and re gapped them and checked wires. What else can cause it?

check the grond near the oil dipstick make sure they are clean and tight that's what mine was even after new plugs wires cap and button and coil

Moisture in the distributor cap, plug wires that are leaking spark, cracked insulators on the plugs, loose injector connections, a failing cam sensor, a failing crank sensor, leaking valves, poor fuel quality, intake leaks, a weak fuel pump, a clogged fuel filter can cause a misfire.

What is it you call a misfire? The rough idle?

1) you might want to do a search on the subject ' misfire'.....am pretty sure you wil be provided with hours worth of reading to give you several ideas.
2) you might want to check for codes

3) It's your CPS ;)

Bet money on ignition.... fire it up and hold a piece of a metal from ground up and down each wire. ... will only jump you a little just enough to wake you up. Especially if its random and under a slight load

So last time I posted this I did check codes and got only 43 which doesn't help cause that's the misfire code. I figured I try to replace wires and see how it would go since its cheap and easy. Well it came back again. So I checked codes again today after the light came back on. it was running ok for a few days and the error light went away. Well I got 13 - 43 -43. 13 is the map sensor right?

91-95 models:
Code 13-MAP sensor pneumatic signal-no variation in MAP sensor signal is detected or no difference is recognized between the engine MAP reading and the stored barometric pressure reading..



And here a link to all the other codes , for completeness
http://www.angelfire.com/empire/auto...ble_Codes.html

Is it likely the sensor pouched? Is there vacumm lines going to it or anything that maybe it?

Found this. http://www.allpar.com/fix/codes/faults/code13.html I'm going to check vacumm lines first.

not sure about the 95, but mine has a little tube connected to it....guess yours too. Checked that?

Thanks for the reply's so far guys one more stupid question. Where is it :P

In the 96 it seems to be on the drivers side engine compartment wall. Not there on the 95... Looked at my air box to follow a hose to it but the only hose on the airbox I can see is the one that goes to the valve covers

So looks like I found it. Its right on the throttle body. The vacuum line is 1 in long or so and goes right to the throttle body it appears to be fine from what I can tell...

Yes, its ' attached' to the throttle body.
If the tube is connected, you might wanna spray the connector with a cleaner.
I'm not aware of any MAP sensor tests, would have to check this in FSM.
Unless that solves the issue, I'd reckon a code like that could result in trying a new MAP sensor.
But I have nil experience with MAP sensor failure diagnosis testing otherwise. I replaced mine 2-3 yrs ago when I was chasing a rough idle. Wether that or the IAC cleaning fixed that back then, I will never know, since I did both at the same time...

I had another thought with error code 43

Thought it might be my coil since that was the original error code.

Well ****ing after 1 hour of trying to get the bolt by the engine mount out :brickwall:

I tested it

I got 1.1 ohms and 11.16 ohms.

Are numbers here normal? or is the 11.16 ohms low?

I saw here http://www.jeepforum.com/forum/f13/c...p-asap-303183/

He got 1.1 and 12.16. I also noticed my coil body is got 3-4 cracks in it as well... Might explain the intermittent problem...

So after replacing wires, coil and dealing with all this crap I replaced plugs dispute them looking good on first inspection. Seems to have gone away. So moral of story is do the easiest solution.