The I-3 Camry

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Ad absurdum per aspera - 20 Oct 2006 03:34 GMT

So my wife was driving our '86 Camry grocery-getter (2SFE engine) and
the idle smoothness and available power suddenly start to feel like it
was hitting on three cylinders instead of the customary four.

I pulled the plugs and #3's spark gap is zero. Grounding bar mashed
right down onto the center electrode, and a piece of its end seems to
be missing too.

Since the engine (unopened original) doubtless has its share of carbon
on and about the head -- it's a bit of a known predetonator under load
on a hot day -- I'm guessing that a chunk came loose and bounced around
until it smacked the plug. What do you think of that? Or do you
think the bit of plug came off and then performed a friendly fire
incident?

(Single-electrode Bosch Platinums, properly gapped, that had been
sparking unremarkably along for many thousands of miles.)

My plan is to apply the Shop-Vac to each plug hole, just in case some
bit of evil still lurks within, and replace all the plugs...
Thoughts?

--Joe

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Rodan - 20 Oct 2006 07:39 GMT

"Ad absurdum" wrote: '86 Camry (2SFE engine)

Rough idle. Low power. Number 3 spark gap is zero.
(Single-electrode Bosch Platinum). The grounding bar
is mashed onto the center electrode, and a piece of
its end seems to be missing. I will Shop-Vac each
plug hole in case some particle remains, and replace
all the plugs.

The engine is a known predetonator under load on a
hot day -- I'm guessing that a chunk came loose and
bounced around until it smacked the plug. Thoughts?
____________________________________________________

I had this happen in a V8 engine with a vacuum leak
near one intake port. The extreme heat from the
lean mixture softened the plug bar until it twisted
up into the center electrode. Part of the tip of
the bar was gone but there was no chunk in the
cylinder; just some fine slag articles stuck on top
of the piston. I guess they sputtered off in small
amounts as the bar began to short the electrode.

The top of the piston was wavy from overheating and
I was worried about the engine so I had it rebuilt.
Since then I am paranoid about vacuum leaks.

Good luck.

Rodan.

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Ad absurdum per aspera - 20 Oct 2006 16:39 GMT

Thanks. Guess I should run a vacuum gauge up the flagpole and see who
salutes. Previously though the engine was a smooth idler by
four-banger econobox standards and topped 30 highway -- blew a little
oil, probably past valve stems/seals, at startup, but that's about it
for misbehavior -- so my initial simplifying hypothesis is that there's
nothing horribly wrong with the engine.

Cheers,
--Joe

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Comboverfish - 20 Oct 2006 17:26 GMT

> So my wife was driving our '86 Camry grocery-getter (2SFE engine) and
> the idle smoothness and available power suddenly start to feel like it
[quoted text clipped - 19 lines]
>
> --Joe

I think you nailed it. The carbon didn't necessarily have to come
loose, it could have been getting thicker over time, finally hardening
to a ground tab bending degree.

I would suggest you use a top engine cleaner like GM X-66 and several
applications at that. With the engine at idle you can use a long
section of vacuum hose, attach it to a common vac port, and suck the
contents of the X-66 right out of the can (pourable version). If you
want to use the spray version, you will need to hold open the vane in
the airflow meter enough to keep the engine idling while spraying X-66
into the throttle body. Shut off the engine as soon as you empty the
contents. You may want to try both methods because each has it's
benefits. It would be wise to do this at night so the solvent can soak
in, but you can start the engine in 15 minutes if need be. Also, be
sure to park outside before doing this as the resulting steam cloud is
quite voluminous.

Someone with textbook or google skills will probably reply "don't do it
or you'll ruin your converter!". It won't cause any problems, I've
done this a hundred+ times with success. Use Nippon Denso or NGK plugs
this time when you replace the set.

Toyota MDT in MO

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