2000 jeep xj 4.0L It only happens after a hot start. Started out pretty mild about a month or two ago and I thought it was heat soak. It's gotten worse over the last week. Has no power after hot start and CEL is flashing when I give it gas. Codes I pulled were P0300(random misfire), PO301 and PO305 (cylinder 1 and 5 misfire). I've put new fuel injectors in and changed both O2 sensors with no change. Pulled the plugs this morning and all look good except number 1-it looks oily and was hard to get out( felt like it had loc tite on it).

I've also been losing coolant at a rate of about half gallon a week. Misfire problems seemed to get worse after I added prestone flush to my system. Its not getting in my oil and I can't find a leak. None of my plugs looked rusty.

Gonna check compression wednesday morning but I'm hoping that sense it runs good cold that I want have any major problems but that oil/crud on #1 cylinder has me scared.

What do you guys think my problem is? Ya'll think the coolant leak is related to the misfire when hot? Appreciate any help.

 

Sounds interesting. Yea, if I had a miss, an oily plug and missing coolant I'd do a compression/leakdown test. Just #1 eh? Has the head been changed that you know of? I think there is a head bolt there that's suppose to get sealant on the threads to keep coolant in. Anyway, let us know what you find.

 

What you describe points very possibly to a cracked 0331 head. It is NOT uncommon with the 00-01 Xj.

The #1 symptom of a cracked 0331 cylinder head is "unexplained coolant loss".

Instead of reinventing the wheel, you MUST read this thread. It is required reading for everyone with an 00-01.

http://www.jeepsunlimited.com/forums...d.php?t=391831

 

Great link TJ. So besides a crack there is also a chance it got swapped because of one, and the problem up at #1 still just might be a lack of sealant on the head bolt.

 

I'm thinking I might have a complete failure. I'm still lookign around the site for info, but I post here for discussion.

CEL came on and upon reading the misfire #1 cyclinde code (P0301) decided to first do the plugs. Pulled the ones on cyclinders 1 and 2 and both had oil on them. I did a compression test on Cylinder 1 and it was way below, 75psi.

I just bought the jeep (already suspect it was a scam...person said they hadn't done ANYTHING to the jeep, but the plugs were brand new). I have not driving but maybe 20 miles, so can't say I've been able to get it hot enough, and due to the suspension being crap (although did just replace the front susp. from a ghetto block lift to a little more respectable RC Series II...rear is next) I can't do a long drive. Alignment is horribly off.

I bought the truck for fairly cheap ($2700) so I'm not pissed (well I am about the seller lying...I can't stand liars...but I'll likely remedy that). Even with a bad motor I'll likely have bought the Jeep...but more like $1900 to $2200.

So with the oil on the plugs...does it sound like the crack situation sound like it might have worked it's why down and failed the lower block too (rings, bearings, etc.). Just thinking I'm better off with a whole new (well used) motor and swap. Of course being DC area...probably no option for less than $2000 (cost me $3300 for new head gaskets on my subaru).

 

"Gonna check compression wednesday morning " You might want to do a leakdown, wet/dry test. Warm it up, pull the plugs and take your #'s. Then add a couple tablespoons of oil to each and go through again. I like 7 strokes. A long vinyl tube is handy to blow a little oil in each plug hole. You might crank it 15 sec or so to spread the oil a bit, before the 2nd time through. If a low one comes up, you can suspect the rings. If it doesn't it's something above.

 

Sounds like heat soak ( you have it yup), and a possible cracked head ,but there are other things to cause a lose of coolant that need to be check first before a new 0331 head casting is swapped on.If you wiped the lower bearing with coolant in the oil, then yes a new short , or long block motor would be a great choice shop around online for a good company and prices.If at any time you have the intake off or can get to it by ways of a new motor have the intake heat coated also header to this will help keep down the temps, and get the factory heat sheild and injector sheilds part # 56028371aa this will remove the heat soak issue.good luck

 

thanks for the replies. I've been busy and haven't had much time for the jeep lately but managed to change out the coil with one from the junkyard. Problem still there. damit The compression test kit I bought wouldn't thread into the head but I'm gonna try to get an adapter or something tomorow. Haven't been having good luck. So far I've replaced the fuel injectors (new ford 3.8L V6), spark plugs (champion copper) , O2 sensors (Bosch- up and downstream) , and the coil.

I played around with pulling the fuel injector wires one at a time while it was acting up earlier today and it appears the #2 cylinder is not firing even though the computer is telling me it's cylinder 1 and 5 that are misfiring, lol. Doesn't change tune at all when 2 is pulled. Also checked fuel pressure and it shoots up to 49psi as soon as I turn the key on (not running) but does seem to leak down pretty quick. When it's running the fuel pressure is close to 49 and stays steady-don't think I have a fuel pressure issue. I'm still getting the p0300, p0301, and p0305. The P0305 sticks with me all the time even when it's not acting up and the P0300/P0305 come on when it runs crappy and CEL starts flashing.

I drove it around for about half an hour after changing the coil and it ran good. Shut it off for a minute and cranked it up-ran fine. Cut it off again and started it 15 minutes later and it was acting up. Check engine light started flashing when I pulled on the street so problem is still there.

It only acts up after being shut off for 15-20-30 minutes and then hot restart. A 1 minute shutdown and restart it runs fine. Once it cools off all the way it will also run fine. I'm scratching my head. I don't have a heat shield on my intake around injectors so I'll get one soon but I really don't think thats the problem since it started running worse around the time the weather was getting colder but who knows. Thanks for the part # -gonna stop by dealer on monday.

This got longer than anticipated so if you made it this far thanks and I would appreciate some ideas of maybe something I am missing cause I guess I'm about to replace the head. I'm thinking about getting a junkyard 0630, rebuilding it, and making brackets for the coil. I hear the exhaust valves are bigger on this head and it flows better. I've got a company truck I can drive in the meantime. Appreciate all comments and I'll make sure I keep the thread updated.

 

a blinking CEL means damage is being done to the cat...

but i have heat soak issues with my 2000 and have had a CEL and yes they drive like crap after it happens until fuel pressure is regulated....you might have a leaky fuel rail and under temps you lose fuel pressure, ive seen this with injectors before and im sure it could happen to your rail, might be something to check out....and since you cant drive it far, just let it idle for awhile, it will get real hotin about 30 minutes. and are you sure it was oil on the plug and not carbon buildup from it running lean? coolant loss really makes me think blown head and or gasket, can you ID any leaks anywhere? drain your oil and check that out too or atleast give the dipstick a good look, and then punch the guy who sold it to you in the mouth after that
keep us updated...

 

well guys , I have a blown head gasket. Moved cyl 1 to top dead center on compression and hooked an air hose up with 120 psi- coolant came gushing out the top of the radiator. Even though its gonna be expensive i'm kinda releived i have it figured out.

Also checked compression and this is what I got-
cyl 1=100dry/ 120 wet
cyl 2=135dry/ 155 wet
cyl 3=135dry/ 155 wet
cyl 4=140dry/ 155 wet
cyl 5=140dry/ 170 wet
cyl 6=145dry/ 165 wet
Motor was warm when I took reading and I turned the motor over about seven strokes. My compression gauge is a cheapo from Harbor Freight so these reading probably aren't 100% accurate.

Do yall think I should go with the same 0331 head new from autozone or get a 0630 junkyard head and rebuild it? I've got a feeling the head thats on it is cracked. thanks for all the help.

 

I buy and recommend my heads from either Clearwater Cylinder Head or Alabama Cylinder Head.

Both are top notch vendors that have supplied thousands of heads to XJ owners with good customer service and a good warranty.

Personally, I'd pass on Autozone.

 

I'm so cheap I've changed only the gasket, if it's clear the old one was the problem. But I also carry my tools and am rarely far from home. Btw, you can put kerosene or diesel in the ports of the head and watch around the valves to see how well they are seating. I'd give my $ to Bruce, owns the local wrecking yard, and Bill, ran a local machine shop. But everybody situation is different. You might want a new "bullet-proof" head.
I'm curious if you did a power-brake test if you would get the same result as you did with the compressed air. With the cap off and it warm, firm throttle with your foot on the brake, see if it geysers.

 

thanks. I've been doing a bit of research and it seems that Alabama and clearwater are the way to go. Does it take long with the shipping and is the shipping expensive? The main reason I was thinking of going with auto zone is the price but I also figured I could pick the head up in a day or two. I'm impatient and also thanksgiving holiday should give me some free time to work on the jeep. I've scratched the idea of going with the older head (0630) due to needing an adapter for the exhaust manifold to fit right. I'm planning on replacing the waterpump, all the hoses, fan clutch, and t-stat. I figure after all this I shouldn't have to worry about running hot and the autozone 0331 head might work alright but I'm still deciding. I'll keep ya'll updated.

 

yeah if my old head has no cracks, and I'm gonna look very good, then I might get it resurfaced and rebuild it. I'm scared to buy a used 0331 casting cause I might not notice the crack until I get home. Most the vehicles in my junkyard aren't wrecked so you've got to wonder how they got there. I'll probably be in rush pulling the head at the salvage yard and knowing my luck I'll get home and find a hairline crack that I missed. The autozone head is about $380 after I turn in the core so I'm still trying to research whether or not these "surefire" heads that autozone sells are decent.

As far as the coolant overflowing-no need to even powerbrake it, just start it up and with in a about five-ten minutes of idling it will be overflowing. I'm not very experienced with diagnosing cyl. head issues and somebody who knows what their doing could have probably diagnosed this without the compression test or pumping air into the cylinder. Live and learn I guess. Anyway I'll keep this updated but it might be a few days. I'm working on the jeep at my moms house (I live in apt. and no room for tools) so it might be later this week. I'll bump this thread cause I'm sure I'll run into something.

 

Figured I'd give an update. I got the head off. Turned out to be more of a pain in the a$$ than anticipated. Couldn't get the bolts loose for the intake/exhaust manifold (the ones underneath) so ended up pulling the head off with the exhaust and intake still attached. Also broke off a couple of the exhaust pipe bolts but I was expecting that.

Anyway the head has a crack in between the valves on #1 cylinder. I really couldn't tell if the gasket was actually blown so I'm assuming this crack was giving me all my problems. Still can't figure why I was getting P0305 when nothing seems wrong with #5 cylinder.

Also found out that my intake manifold is cracked around #6 cylinder. It's cracked right there where it bolts to the head- I guess it might be called the flange. Gonna pull another intake tomorrow at junkyard. Lucky for me their having a 50% off sale this weekend. I already went out there earlier today and got a rear bumper(paint matching), 95' ford taurus E-fan, and some weatherstripping all for $55.00.

If anyone reads this and has any advice for when I reinstall my new head I'd appreciate it. I'm planning on torqueing the intake/exhaust manifold while the head is still out of the jeep and sitting the whole thing in. Can't see any way that I'll be able to get my torque wrench in there to tighten the bottom side manifold bolts. I might try to get some pics of the cracked manifold and head up but I'm not too good with computers so maybe not. Thanks for reading.