CEL and misfires on two cylinders?!?

[98XJblack]

Hey everyone first post here for help.

1998 jeep xj 4.0. I have a cel for p0302 and p0304 misfires on cylinders 2 and 4. I am starting exhaust all my resources on this. Swapped out the injectors to different cylinders no change. I had thought that it could possibly be the spark plugs cause I pulled them out and they were moist with gas possibly from no spark so New spark plugs and rotor no change and I've done spark tests on all my wires with the same result no change! The engine does do some funky stuff it'll bogg down to almost dead and then kick back in to a proper idle. Now I've also changed the CPS as well for this issue but still nothing.

I'm thinking I need to check compression next but I'm also open to other possibilities that could lead to these misfires.....

Any help is much appreciated

[XJ Wheeler]

Sorry, i actually don't have an answer for you but wanted to say most likely the holiday has taken some people away from the forum. So, its not you or that people don't want to help. Please, be patient. We have some VERY knowledgeable jeepers on here that i know would be glad to help you.

Welcome to the site too.

[nickxj94]

Check fuel psi first, then compression test, check your grounds to engine fenders battery ,then report back, Merry Christmas

[98XJblack]

Ok so I haven't gotten to the fuel psi or compression and grounds yet but I wanted to add that I pulled the spark plugs from the two cylinder misfiring and they are wet with what looks like oil and gas? I'm thinking that there is a possibility I have a busted seal in the cylinder head somewhere. I'm assuming this could also cause a misfire and if so do the plugs need to be changed now or just cleaned and will any residual oil in the combustion chamber be burnt off once this is fixed or am I totally screwed?!?

Thanks and ill hopefully getting to those tests tomorrow when I have the diagnostic tools.

[nickxj94]

I would change the plugs

[4.3LXJ]

Yes. Plugs probably need changing. Get new plugs and install them. If the misfire persists, then pull the affected plugs and turn the engine over with the key on. If they don't spark, then replace the wires.

[98XJblack]

Ok quick update and I'm dreading the worst at this point fuel pressure is solid! However compression is as follows (this is where things get bad) cylinder 1-150, 2-50, 3-90, 4-90, 5-130, 6-150.

Where do I go now, obviously into the engine, I'm worried this was a bad buy.

[nickxj94]

Rings are probably shot

[98XJblack]

any chance it could be anything else, cracked cylinder head because the rings to me wouldn't explain the presence of oil in my combustion chamber?

seeing a lot about cracked heads in some other threads.

thanks

[gary63]

you may have carbin holding the rings in on the pistons you can try seafomethe engine or flushing it. you coud have scratches on the cyl. wall witch is lotting oil pass by.if that is the case you can try xado http://xado.us/
there oil treatmont fill in small scratches and puts a coating on metal parts.
I have use some and test some right now. I put some into a powersteering pump that had a very loud howl it almost elemenated the noise it is very quit now.

[4.3LXJ]

If you get into the engine, the first thing to do is rebuild the head. If you are getting that much blow by, I think it would be spitting oil and you would likely have fouled plugs on all cylinders

[98XJblack]

I am going to investigate all these things further. I've been workin with my mechanic friend and he added that if the rings had gone I would have had some substantial oil loss, which I haven't noticed. But my eyes might be wrong in saying I see oil on the spark plugs but they do seem dirty but it could just be wetness from the gas and some residue.

I will inspect the head and try the metal conditioner this weekend.

[gary63]

check you valve giuds you may have 2 of them starting to go.

[XJ Wheeler]

Could be several things. All requiring pulling the head minimally. Best case, head gasket.

[nickxj94]

Take a qt of trans fluid start the engine dump it slowly in the throttle body while keeping it about 2000rpm till the qt is empty it will smoke like a freight train for a while but helps clean and boost the compression I've done it on a few of my rigs sometimes it's carbon build up on the valves causing low compression

[98XJblack]

Update on my progress, seafoamed all the cylinders and got some nice results. The engine is running much better I will be sea foaming fully with the intake manifold as well. I'm still misfiring on cylinder two, I will be doing a compression test after adding oil to the cylinder to eliminate a piston ring issue. But things are definitely starting to look up.

[98XJblack]

New engine coming soon haha totally sucks but its definitely the piston rings! Seafoam worked great and cleared up misfires on any other cylinder except for cylinder 2 of coarse so we'll be doing the swap soon.

Thanks everyone for the help on this a lot of great info and tips.

Jon