Black Sooted plug

99 Tacoma 4 cylinder @ 68k on the clock. What would make # 4 plug have lots of soot on it. Bad injector ?
Reply to
W.T. MC GLYNN
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Or bad plug wire, or distributor cap. Either way, the cylinder is mis-firing.

Reply to
MrFixit469

Leaky valve stem seal?

Reply to
Jeff Strickland

Thanks,it was a bad wire. Went ahead and replaced all wires and plugs. It's humming like a Toyota again. Happy Holidays...

Reply to
W.T. MC GLYNN

wouldn't a leaking valve stem seal make a plug oil fouled, and not carbon fouled?

Reply to
isaac

I suppose, but aren't oil and carbon both black?

Reply to
Jeff Strickland

It is a matter of DEGREE. A small amount of oil passing from the intake valve stem seal and through the combustion chamber may result in some caked, white colored deposits on the spark plug. But as the oil passage increases, (ie, the engine starts smoking visibly after prolonged idling), then the spark plug could become wet ... far beyond any caked on deposits.

Reply to
Philip

Let's look back at the question...it was about the plug having SOOT on it. Soot is DRY, which would rule out oil fouling which is WET, eliminating leaky valve stem seals. Soot indicates an overly rich mixture caused by a improperly functioning fuel delivery system or an improperly functioning ignition system. 90% of the time, this is caused by either an old or damaged distributor cap, a bad plug wire or a damaged spark plug which was dropped at some time and the insulator cracked. All the afore mentioned will result in less than optimal spark energy travelling through the gap at the end of the plug. Less fire during the combustion process means less of the Air-Fuel mixture is burnt resulting in excess raw fuel being left in the combustion chamber which is then DRIED by the heat left as a by-product of the combustion process. This causes DRY carbon deposits to be left in the combustion chamber and on the plug tip, hence the "Soot" he found on his plug and the bad Plug Wire he found to be the problem.

Reply to
MrFixit469

Reply to
Bill Hall

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