On Mon, 26 Oct 2009, Paul Hunt wrote:
> One white plug does indicate a leak to that cylinder somehow, although as
> cylinders are paired that's not strictly logical, unless it is on the No.1
> side of the gasket which would affect No.1 more. However vacuum leaks
> usually tend to be 'stable', not come and go like electrical problems. The
> HT tests are really only valid if you can reproduce the problem with a timing
> light connected. You say it only happens at speeds over 45, but engines are
> usually rev affected not speed affected. If it happens at 45 in top, how
> about the same revs in 3rd? And 45 in 3rd as opposed to 4th?
At this point, we are going by my 1 AM memories, so keep that in mind.
When it was happening, the one thing I noticed was that engaging or
disengaging the overdrive did not help. The same thing would happen
with the OD on vs off. I don't remember needing to change my foot
when switching the OD, so the throttle position would be the same.
Yesterday, when I drove to the grocery store, I was able to go about a
mile at a steady 35 in 3rd, which is IIRC close to the same revs as 60
in 4-OD, but quite possibly a different throttle position. If it's
not raining when I get home from work tonight, I'll go for a test
drive and experiment.
Regarding the plugs, I can't remember, is it the outside or inside
plugs that tend to run richer in the pair? My initial thoughts were
that I'd see a difference between 1 and 2 and a similar difference
between 4 and 3 due to airflow differences on the intake. I didn't
think much of the white plug at the time, which is why I need to look
at it again more carefully.
I also am unsure as to how quickly plug deposits change. After
driving for 70 miles at highway speeds, I have about 2 miles of 45mph
descent into town (almost no throttle) followed by about a half-mile
of 25mph climbing up a mild hill to my apartment. So what I saw on
the plugs may not reflect the reality of what the engine would tell me
at the time of the problem.
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