Misfire at start-up...head gasket??

[FPGT24]

Hello all, i picked up a 00 XLS with the OHV V6 and am trying to figure out if it has a leaky head gasket or if it's an ignition related issue. The Ex has 210,000 miles. Upon a cold start or a warm start (after its sat for 30 mins or more) there is a misfire on one of the cylinders for approx 10 seconds. There are no codes thrown. My buddy who has a good deal of experience with the Cologne OHV engine says hes pretty sure that the head gasket is starting to leak on one of the cylinders. The radiator was down about half a quart of coolant, nothing significant. My buddy believes that a small amount of coolant is seeping through the head gasket and into one of the cylinders and that the engine is burning the minuscule amount of coolant off before the ECU stores a code for the misfire. I am not experienced with this engine like I am with the SOHC version, so I'm seeking any knowledge that you folks may have before i start throwing money into replacing the ignition components. I'm hoping its just a coil or plug, but usually in my case it's the worst possible scenario.

 

[Tedybear]

Not sure about a head leak.... 00'? That should be OBD II and might be able to snag which cylinder it is using the misfire monitors.

I'd figure out which cylinder it is, and then pull the spark plug and let it sit. While the plug is out, check for possible ignition issues..and the condition of the spark plug. (carbon build up....does it look 'steam cleaned'....etc..) Endoscope camera/inspection camera might come in handy to see if there's any puddles of coolant sitting on the piston.


If there is a coolant leak, it could be from intake manifold as well. (depending on which cylinder it is...There's likely a couple of ports within a close distance that might be seeping.)

S-

 

[Robman]

Change the plugs/wires, top up the coolant and drive it

 

[Turdle]

^^ this, lay the plugs out in order and take a real good close up picture of them to show us please.

 

[FPGT24]

@ TedyBear, all 1996 and newer vehicles are OBD2.

I'm not sure how to figure out which cylinder is causing the misfire as I do not have a high-tech scanner. Autozone and advance no longer do the free engine scanning tests with their top end scanners, unfortunately. This is going to be a pain-staking process of tracking down an intermittent issue like this, it means i'm going to have to pull a plug from a diff cylinder every morning when the engine is cooled off. i may just say F it and throw in some new plugs and wires to see if theres any difference. i will post a pic of each of the plugs when i have them pulled. any recommendations for plugs? i have never replaced plugs on any explorers before so i am not familiar with what makes these engines run the best.

 

[Tedybear]

I'm aware of the 1996 being obd II. I'm also painfully aware that people swap out harnesses and engines more then a few times....

It's not needed for a 'top end' scanner for misfire monitors. I've got a laptop program and interface cable that does quite well for OBD II work. It does not cost anywhere near what the factory or high end systems run. (Heck, the one for our VW runs VCDS and cost under $20 when I purchased it. And the basic VCDS does almost everything I need.... Just need to ask around for low cost alternatives that work with a laptop)

Heck, lately that's been getting more use then most other tools in the box.





A few youtube links that might prove interesting. One of the best diagnostic instructions BAR NONE. Paul Danner. (Scanner Danner) with Eric the car guy. (Both exceptional techs.)

Another play list with a gentleman discussing how to locate a misfire when the scan tool doesn't do the trick. I glanced over it, good info that might help.

Spark Plug appearance might prove useful for this. I'm not sold on the coolant leak quite yet, not when ignition issues and vacuum leaks are still possible and have not been removed as a possible source.

 

[FPGT24]

Did some brief work on it today, it finally threw a code at startup its P0304. I am going to pull the plug in the morning and see whats up. Will post the results.

 

[FPGT24]

UPDATE:

happened to be a faulty NGK V-power spark plug that failed. replaced it and it runs good now.