Dcoy

My 2000 Cherokee keeps throwing a p0304 ( cylinder 4 misfire ) and some sort of EVAP emission control leak ( p0455 or p0456 or p0442 ). When I start up and go sometimes the engine light will start flashing and the jeep sputtering and it won't rev over 3 grand. Odd thing is if I pull over and turn it off then start it back up it runs fine. I changed the plugs and they all looked normal, and the coil rail is just over a year old. Any ideas, coils be bad already? Or possibly an injector?

JamDeeper

I had tthe same on my 00.. it will do that when its hot (sputter) .. you'll have to get the evaporated lines smoked out to find your leak. As for the misfire. Be sure you have copper core plugs gapped to OE. It cleared up my misfire. As for the sputter. I believe its the head gasket slowly going out. But that's just my thoughts...

Dcoy

Most of the times when it sputters with the cylinder 4 misfire its 5am on the way to work about 2 minutes down the road, but its not everytime, maybe twice in a tow week period. The other times it runs great. yeah I have copper core plugs in it. Id think if the head gasket was going bad it would happen all the time.

Kalali

Regarding the P0304 code, are you loosing any coolant? Check under the oil cap on the valve cover and look for milky residue. How many miles on the car?
If you have any unexplained loss of coolant, i.e., no leaks, etc., that combined with the P0304 (or P0303) is an almost sure sign of a cracked head. Otherwise I would switch injectors with another cylinder to rule that out. And I suspect a coil would go bad only after a year.The crack is right where the coolant will ooze out into the oil passage near cylinder 4. Depending on how long this goes unnoticed. the bearings get damaged resulting in low oil pressure and compression, again all near or around cylinder 4. I'm telling this from personal experience. My P0304 code came right back even after putting a new head. My oil pressure is within spec but I'm willing to bet I've lost some compression on cylinder 4. Going to test this weekend.
I'm sure more knowledgeable folks will correct me if I'm wrong.

P.S. Why did you replace your coil last year? Symptoms?

LYKOS

Mine was doing that last year. In fact, I still have the evap code as I haven't fixed it yet.

I was getting BAD heat soak issues. Sometimes so bad I could barely make it to the side of the road.

Changed plugs, no change.

I was pulling the plugs one day to check them and jacked up my coil packs. (Don't ask how, I just did."

After I replaced the coil packs the problem went away...

Kalali

Just to be sure we are on the same page, were you getting a single cylinder misfire and replacing the coil rail fixed it? I'm curious because each of the three coil packs on the rail fire two plugs at the same time; 3&4, 1&6, 2&5, and the likelihood of only one misfire should theoretically be really low.

By the way, heat soak is usually caused by the fuel in the injector(s) getting hot after the car sits for a period of time after a long drive. Nothing to do with spark.

jeepguy72987

try the easy stuff first but i belive you have the 0331 head and there known to crack.

Dcoy

I replaced the coils last summer for no reason.... turned out it was fine but I just had the normal heat soak issue on the #3 injecter. The jeep has 142k on it and most of time runs great. I do have a small coolent leak up front on my stat cover but no where else that I know of. I just don't understand why if I turn it off then start it right back up it runs fine. I would think if I had head issues it would do it all the time and wouldn't there be a noticable differance on my plugs when I changed them the other day. I plan on swapping the injectors this weekend.

LYKOS

Yes and I was getting a code for number three misfire. For whatever reason replacing the coil rail, or something I did while replacing the coil rail fixed it.

Kalali

Thanks. The reason I'm asking is because I was getting a cyl 4 misfire and had a cracked head. I replaced the head but still get the cyl 4 misfire. I am going to do a compression test and if cyl 4 passes the test then I'll go ahead and replace the coil rail. The strange part is the misfire code is intermittent.

Dcoy

heres another tid bit to my problem, it acted up a mile from my house this morning on the way to work ( 65 degrees out), at a red light i shut it off and started it right back up and ran fine the other 15 miles to work. Got off work and put close to 100 miles on it in 95 degree weather ( yes 95 in PA, who would have thought ) somtimes doing 70 on the toll road and in city traffic and it ran just as it did new. WTF

Dcoy

[QUOTE=Kalali;1862845]Regarding the P0304 code, are you loosing any coolant? Check under the oil cap on the valve cover and look for milky residue. How many miles on the car?
If you have any unexplained loss of coolant, i.e., no leaks, etc., that combined with the P0304 (or P0303) is an almost sure sign of a cracked head. Otherwise I would switch injectors with another cylinder to rule that out. And I suspect a coil would go bad only after a year.The crack is right where the coolant will ooze out into the oil passage near cylinder 4. Depending on how long this goes unnoticed. the bearings get damaged resulting in low oil pressure and compression, again all near or around cylinder 4. I'm telling this from personal experience. My P0304 code came right back even after putting a new head. My oil pressure is within spec but I'm willing to bet I've lost some compression on cylinder 4. Going to test this weekend.
I'm sure more knowledgeable folks will correct me if I'm wrong.

No coolant in oil, changed it Sunday when I swapped 2 injectors and it did it again on the way to work this morning . I pulled over shut it down then started it back up and ran fine..... still a cylinder 4 miss firing. Is there any chance that the cam sensor can be going bad?

Dcoy

I just can't see it being the head cause it only does it a few times a week on the way to work. Runs great on the way home and all the running around I do after work. Then when
it does do it all I have to do is shut it off and restart it and it runs fine.

Kalali

Aside from the misfire code does the engine have a slight rough idle, vibration, etc.? The best way to diagnose an actual misfire is listening to the tail pipe and see/hear if you detect a miss.

tjwalker

The 00-01 is very susceptible to "heat soak", but the most common misfire issue with that is with cylinder 3. I suppose it is possible for it to be cylinder 4. You could try wrapping that injector in heat shield.

But as you mentioned this happens a few minutes down the road, I don't think it's heat soak.

I'd start by changing your spark plug. Even if it's newer. You must eliminate the simple stuff first. And be sure that the gap is .035 NEVER trust spark plug gap out of the box.

A compression test is never a bad idea. A good "snapshot in time" of the internal condition of your engine. The spec for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

Good luck and keep us updated!