jeanjellybean1@webtv.net (w.t. mc

99 Tacoma 4 cylinder @ 68k on the clock.
What would make # 4 plug have lots of soot on it.
Bad injector ?

mrfixit469

Or bad plug wire, or distributor cap. Either way, the cylinder is
mis-firing.

jeff strickland

Leaky valve stem seal?

jeanjellybean1@webtv.net (w.t. mc

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

isaac

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

jeff strickland

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

philip

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.
--

- Philip

mrfixit469

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.

bill hall

It sure is nice to see someone with some mechanical experience and knowledge
to finally respond to a question from a less knowledgeable poster!! Good
show Mr. Fixit
Bill