Rough idle, now won't start and giving CEL P0302

[mikebonn]

Long time lurker, first time poster. I can usually find everything I need here by searching, but I'm stumped by this problem I'm having...

Car is a 2000 C2 with 91k miles, and has run strong with the normal maintenance for the three years that I have owned it. I should also note that in the last year I have replaced plugs, coil packs, MAF sensor, and cleaned the throttle body.

Not sure if this is related to my problem, but I was blowing leaves from my driveway last week and also blew them from of the spoiler fins of the car. Anyway, the next morning the car started, but the engine was running very rough with a loud knocking sound. I quickly shut it off and let it sit for a few days until I could take a closer look. The CEL was on and returned the P0302 code.

After inspecting the air box and throttle body, I didn't see anything unusual beyond the air filter, so I ruled out any foreign object being blown into the engine from my stupid leaf blowing episode. I fired it up and it was still idling very rough with white smoke coming from the driver's side exhaust. Next, I replaced the coil pack and plug from cylinder #2 (assuming P0302 was denoting a misfire in cylinder 2), but I still had the same issue. Of note, the plug that was removed from cylinder #2 was wet and smelled of gasoline. From this, I assume that it was getting fuel, but not getting a spark. Now, the car won't start at all - it turns over and sputters, but won't idle.

Based on my research on this forum, I feel like I've eliminated some of the easy/cheap fixes. Any other suggestions before I have it towed to the dealer? This car is my hobby - I have time, some tools, and a little aptitude. I'd prefer to sort this out myself, but I have a bad feeling about this one.

Mike

[xmac]

I think the leaf blowing is a red herring.

Pull out the coilpack and check the resistance between the 2 outer pins (there are three pins on the coilpack) and make sure it is between 3-7 Ohm. I realize you mentioned that you replaced it but you could check to see if something is damaging the coilpack. Not that it is the same symptom but another member found a short in the wiring that was damaging a coilpack. http://www.renntech.org/forums/topic/26119-blown-ignition-coil/page__fromsearch__1

If the coilpack is OK, it could be bad gas, water in your fuel, coolant leaking into the cylinders (cracked head or head gasket). Are you having to add coolant/water frequently? I would also take out a few more spark plugs to see if they are also wet - both from the same head and the opposite one.

[mikebonn]

xmac - thanks for the help!

The coil packs on that bank were fine, so I removed all three plugs as you suggested. The plugs from cylinders #1 and #3 were also wet and smelled of gasoline. However, when I removed the new plug from cylinder #2, several ounces of coolant poured out of the cylinder, and it continues to slowly drip out with the plug removed.

I haven't had to add coolant recently. It is a tad low now, but not by much. The oil on the dipstick looks fine too, but I never ran the engine after the misfire began.

Sounds like cracked head or head gasket...bummer. Any way to determine one versus the other without taking the engine apart? I've got a spare car until my son returns from college in June, so replacing the head gasket could be a winter project. However, a replacement engine does not make much sense for this car.

[logray]

The head gaskets on these cars pretty much never fail, sorry about the bad news!

Repairing a crack in the head is certainly do-able and can be done DIY for $2500-3000.

[xmac]

sorry to read the bad news. You should read through this post:

http://www.renntech.org/forums/topic/29334-cylinder-full-of-antifreeze/

[mikebonn]

Well, after going through the stages of grief, I have finally accepted that I likely have a cracked cylinder head.

Thanks for the great links, this provided me with the inspiration to try this repair this myself as a winter project, and I am actually pretty excited about it.

Since I am going to be pulling the engine from the car, what else makes sense to replace on a 91k mile car? I was thinking that replacing the clutch and water pump are no brainers, but what other things make sense to replace while I have the engine out?

[logray]

If you don't plan to crack open the case and are only going to remove the heads, I would replace just about everything in the heads (both of them) and outwards.

Variocam actuators/solenoids, gaskets, seals, orings, AOS, paddle tensioners, ramps, spark tubes, plugs, lifters, chains, valve springs and other related valve hardware, valve guides, oil pumps, bolts, crank breather, oil fill tube, etc. etc. etc.

That will up the previous given estimate by about $2k bringing it closer to 5k for a quality DIY job.

Keep in mind you'll need to spend around 500-600 in machine shop services for a QUALITY cracked repair & valve job (full head rework). Apparently the best head rework in the world costs about 1500 per head... but don't let that scare you unless you are an absolute perfectionist and money is no object.

That being said however, if you are on a tight budget you can reduce the parts list above substantially (back to the 2500-3000 range) and still have a good running engine (albeit with some compromises reusing 91k parts).

Edited December 8, 2011 by logray

[mikebonn]

Well, I removed the engine and disassembled it piece-by-piece to find the classic d-chunk crack in the #2 cylinder wall. I have been closely following logray's engine rebuild and I plan to follow a similar route as him with LN Engineering's Nickies. I'll also be upgrading the IMS bearing along with most of the other wear parts in the engine.

I'm almost glad I had this failure, because if this rebuild goes as well as logray's, I'll wind up with a much-improved, more powerful, more reliable engine for a fraction of what it would have cost to scrap the car and try to find anything equivalent. It has been a great project thus far and I am looking forward to the finished product.

[fpb111]

Bad that your engine fell victim to D-chunk. Good that you decided on a DIY. It sounds like you will end up with an improved engine. Please keep us informed of progress.

[logray]

Well at least you caught it before it became a total loss. Good luck with the rebuild.