Jeep Motor ?

[Fred]

This is a 1992 XJ with 4.0
So a little background. I ran 1/2 day on the trails a couple weeks ago and all of a sudden on my way back to the trailer the jeep started misfiring and stinking of raw fuel. It was and still is throwing a code of 27.

OK after a full day of work heres what I found today. The jeep has been misfiring and smelling strongly of gas.

First thing we dove into the tune-up. Changed plugs, wires, fuel filter, air filter, oil filter, cap and rotor. After that it was still running stupid and we could smell a STRONG gas smell. Well I noticed the valve cover was leaking some and you could see it bubbleing at the manifold. We check the oil and it is VERY thin and wreaked of gas. So at htis point I say ok lets pull the valve cover and see what we can see, thinking a valve may be stuck, or bent. We do so and all the oil inside was "water thin" due to gas in it. We chack it out under there and everything looks good, so we kick the motor over and everything was moving as normal. Then we start it and let it run a hot second, it ran FINE and the code cleared (this is with no valve cover).

SO We think lets go replace the valve cover gasket, change the oil, and clean all the electrical connections. We do so and fire it up, mis-firing again and blowing white/blue smoke out the tailpipe. Out of curiosity we remove the filler cap and start it and it ran fine with no smoke. We put the cap back on and it ran like crap again smoking again.

At this point I parked it and called it a night. The best pronosis we made was either a stuck, bent, or burnt valve. Basicly solution would be a valve job or get a new head with valves in it.

Does this sound like we are on the right track? Anyone have ideas? Anyone care to confirm or debunk our prognosis?

[Jeeper guy]

Did you check injectors? The miss might be caused by a clogged injector... Is it missing in all cylinders or just one?

[Fred]

I put a stethoscope on the injecotrs and could hear them firing. Doing a compression test on it Tues and possible going to replace the distributor

[OJTV8CJ]

"Normally" - white smoke means that the head gasket is gone.  White smoke is caused when the water/antifreeze is combusted.  Blue smoke means you are burning oil.  Usually a burnt valve or bad rings.

The only part that is stupifying is that it ran fine with the valve cover off.  There shouldn't be enough pressure in the valve cover to produce a miss or anything.

My bet is cracked head for 100 Alex.  Although in all my time around Jeeps I have never seen a 4.0 with a cracked head.  So I reserve the right to change it to bad head gasket.

[Fred]

The ususal symptom of water in the oil is not present at all, and the water level never dropped

[CRAZY LARRY]

have you check the fuel pressure regulater?

[Jeeper guy]

Ive see one 4.0 head crack and that was a kid that brought the head into oreillys while I was in there once, I was a 4.0 out of Cherokee... Ill take cracked head for 100... Although for freds sake i hope its not. So fred is there pressure in the valve cover?, So when you pull the oil cap off it runs fine??? Not sure if pcv system whould have something to do with the pressure in the valve cover? What does code 27 mean?

[LoneWolf]

Check your fuel pressure. Your regulator could be the culprit of gas in the oil; to much pressure... to much gas to burn; what's left over has no place to go but down to the oil... it would also foul your plugs causing the crappy running.

A clogged injector won't cause oil in the gas, but one that is stuck open will. You can check to see if you have one stuck open by putting a gauge on the fuel line, start the engine to bring up the pressure... shut the engine off and immediately pinch the feed and return line... if your pressure drops, you have a injector stuck open.

Also I'd check your timing... since you say it just happened all of a sudden.

none of the above explains the white smoke. Was it smoking white before you changed the oil/filter? White smoke as OJTV8CJ said; is water getting burnt in the combustion chamber. I don't know of any other way white smoke would come out the tailpipe.

[Fred]

Its a white/blue smoke. The pressure regulator and or a stuck injector is My guess as the culprit. 27 is an injector Code. so my majority vote is going to stuck injector

[bronco72]

any updates on this?