[s-cars] spark plug diagnostics

[Ray Tomlinson]

Hi all,

Spent the weekend chasing an intermittent boost loss.  Car was pulling boost
above 20-21psi - felt not like a "miss", but like a fuel delivery issue,
common on the early CIS cars.  Of course, and only AFTER checking everything
under the sun, I replaced the plugs (only 10-12k on the plugs), and
everything is back to normal.  Cylinders 1-4 looked great, but #5 had very
disturbing coke buildup on the plug, which I believe to cause a misfire
under significant load.

Whitish buildup on the plug initially led me to believe overheating, but
both oil and coolant look good, but then I thought of something.  During the
winter, I ran Mobil 1 0w-40, and I noticed a milky white deposits on the oil
filler cap, which is generally consistent with condensation and short city
trips where the oil does not heat up sufficiently, but not uncommon for a
city car in the northeast.

I just changed over to Redline 15W-50 for the "summer", and I intend to
watch the plugs over the next 1500 miles to see if any plug evidences the
same coking, but I am interested to know if anyone else has noticed the same
coking with M1 0W-40.

Ray Tomlinson
Boston


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.569 / Virus Database: 360 - Release Date: 1/26/2004