I have had a another reoccurrence of this problem which seems to come and
go. At various times in the past, I have thought this was due to poor
electrical connectors (distributor, idle stabilizer, air flow box, etc),
ignition problems (plugs, wires, timing, etc), or fuel (bad injector, fuel
pump). I have meticulously checked all these things, as well as the temp
switches, vaccum lines, and the cutoff switch on the air flow throttle.
ALWAYS, the problem goes away as mysteriously as it appears, and I conclude
that whatever I did last cured it. Unfortunately, when it reoccurs after
several months, that same "cure" doesn't work and I start all over.
Sometimes it all seems like that movie, "Groundhog Day".

And it's starting all over again this week. Here's some of the symptoms
(this is an 85 Vanagon, manual trans):

1) From a cold start, starts good and runs good for about a mile, then
begins to "stumble" (like it misfires, or momentarily is caught between
quiting and running). Especially prone to do this when starting up from a
stop light. May continue to stumble even at speed for the next few minutes,
then seems OK.

2) From a warm start (engine hot, shut down for 5-10 minutes, and
restarted) may very randomly and infrequently refuse to start. Cranks good,
may try to kick over during the first few seconds, but then dies and just
cranks like there is no fuel/spark. Generally starts OK after I spend 10
minutes trying all the things you can do it in a parking lot without
looking like a total fool.

Over time I have favored two theories as to the cause - ignition problems
and warm/hot weather.

The ignition theory is supported by the fact that replacing plugs, playing
with the timing, etc. sometimes seems to solve the problem. I use W7DTC and
the current set has about 8000 miles on them. I am suspicious of the coil
since it is still the original, but it checks out per the ohmmeter test in
Bentley. Is this test reliable? Is there another test?

My warm or hot weather theory is new and is based on my realization today
that this problem seems to recur only in during the warmer parts of the
year. I began to develop this theory last fall when the problem went away
as unpredictable as it came. Now this week we are having 80 degree days
here and I am starting to have these problems again.

Could it be that the warmer air is a little too thin for the idle setting?
However, the plugs look like the engine is OK or possibly slightly lean. O2
sensor is Bosch with about 49000 miles; could it be going? (But I had this
happen last summer when the sensor was a lot newer).

I'm going to tear into this on the weekend so any thoughts will be
appreciated. Also, last I looked the archive was gone. Does anyone have the
notes from the archive on this?

*****  John Clavin  |  jjc@bga.com  |  Austin, TX  ***************************