MGRepairs

I just purchased this '95 LS 400 with 140K miles and drove it about 2K trouble free miles. Then the other day it stared idling rough at a light. When I resumed highway speed, the check engine light came on as did the 'traction off' light. It ran very poorly. Took it to an independent shop who ran the codes. He said it showed it was missing in two cylinders, but he could not tell me why. I then changed the plugs, wires, caps and rotors, all with genuine factory parts. No change in condition, perhaps even worse.

When removing the number seven plug, drivers side rear, I noticed anti-freeze in the spark plug tube. The spark plug boot looks like it had anti-freeze fluid on it for awhile. That plug was the only one that did not look perfect, it has some black soot on the tip, and the outside looked to be in bad shape. Compression varied from 220 to 240 in all eight, with number seven being on the high end.

Ever heard of this condition? Do the tubes ever leak, or must it be a cracked cylinder head? If the seepage is slight, can it be ignored?

Thanks so much for any advice or suggestions.

JBrady

Wow, strange problem indeed. Either the car had antifreeze accidentally spilled into the tube? Or, the water passage has a crack in it allowing AF to seep into it. If the latter is the case... I would also be concerned that water/AF is leaking into the crankcase as well. Check the oil, look for foaming and/or white residue, look for too high an oil level (water displacement). Unscrew the oil drain nearly all the way but just barely let it weep around the last thread or two, water is denser than oil and will come out first if present.

Again, very odd, keep us posted.

MGRepairs

Thanks for the thoughts and suggestions, Houston. Weather conditions have kept me from doing much more than chatting about the problem. Most I talk to said it must be head/head gasket related, however, one fellow, who claims to be a dealer technition, said that this phenemon is known to happen, and often goes away without any further trouble. I hope he is right!

Oil level seems correct. No visable oil in the anti-freeze, no frost or discoloration of either oil or coolant. I will try your oil plug trick as soon as it thaws outside.

It happens that I drive a '95 Isuzu Rodeo V6 which tends to accumulate oil in the spark plug tubes. Its an issue of the tubes not being properly sealed and seated in the head. Not a major problem as long as the plug leads stay healthy.

I plan on posting again once I learn more, in the meantime, all thoughts and suggestions are welcome.

MGRepairs

Did I say coolant? Turns out it was rusty water from having been pressure washed. Water froze overnight, working its way under the spark plug lead, causing the engine to miss.

Al is now well!

JBrady

Lends credibility to my guess of "spillage" as the culprit...

Glad you found the problem and it was NOT anything serious.

Lextreme

It might be valve cover gaskets. My Cobra had a lot of missed fire due to bad valve cover gaskets. Bad valve cover usually have oil in your spark plugs.

BrianV

My dad used to pressure wash his engines every week. Similar things would happen (water in spark plug tubes). This was on his old 70's benz's and stuff, so back then there wasn't nice plastic coverings everywhere. Apparently all the water on the spark plugs would make the ride rough for the first few minutes and then it would go away. However, somehow it screwed up his Cat Converter as one day it turned into a glowing red orb that fell off on the highway because it got so hot.

Now he only does the pressure washing once a year or so.