What a vacation... Cars will always choose the worst possible time to break
down... 300 miles from home! I got back from my two week vacation to Maine
last weekend. I'll try to give the short version of the story.
My car gave me trouble starting when I got about halfway there. It was
running poorly and backfiring through the intake and exhaust, and had no
power. I filed and re-gapped the points and it ran much better, got me up to
ME. I had to re-agap the points a couple times as they kept getting out of
whack. Before I left I had replaced the spark plugs, when I got up there I
replaced the wires, cap, rotor, points and condenser. This greatly improved
the cars performance, but it still ran poorly, thoguh much smoother. I
backed off the vacuum advance by tightening it two turns and that got rid of
the pinging that had developed since I left NJ if I used anything but 93
octane. Now back to 89 and running better.
When hauling ass up hills at WOT or near it there are occasional wisps of
light grayish smoke from the exhaust. When moving at a higher speed and
letting go of the gas pedal there is light backfiring thorugh the exhaust.
At one spot in the throttle when under heavy load (climbing hills, etc.) I
will hear a light backfiring, can't tell if it's through the exhaust or
intake. Exhaust has a couple holes, which may be contributing by allowing
oxygen in to any unburnt fuel while it's still hot.
Did a compression test tonight. Engine was warm and cranked 4 times for each
cylinder, also recorded is plug color. Plugs have ~ 1,500 miles on them.
Cyl | dry | wet | plug color
1 | 155 | 185 | white/light brown
2 | 150 | 165 | white/light brown
3 | 155 | 180 | white
4 | 150 | 180 | white
5 | 120 | 135 | white
6 | 60 | 70 | dark brown
7 | 155 | 170 | white
8 | 155 | 180 | white
This indicates to me a blown head gasket, from low compression on #5 and #5
(next to each other), which from the wet test does not appear to be from
worn rings. This hypothesis is supported by the white plug color on #5,
which was likely steam cleaned by a small coolant leak into that cylinder.
Plug wire #1 was loose and not clipped on. This likely resulted in a misfire
which would partially explain some of teh backfiring and rough running, as
well as the light brown color when most of the otehr healthy cylinder plugs
were still white and looked practically new. Also, a coolant leak into
cylinder #5 would easily account for the light grayish smoke when reaching
WOT under load. I also noticed the coolant level in my recovery tank (tube
from radiator ran into non-functional windshield washer reservoir) was a bit
low, maybe 1/3 full. It was 3/4 or more full when I left for ME.
My other theory, which is more wishful thinking than anything is that the
valves are adjusted too tight on cylinders #5 and #6. That would result in
lower compression and could very well cause backfiring. This is rather
unlikely though, and the evidence points to a head gasket, warped head, or
some other problem of that nature.
What do you guys think the problem is? Also, is my thought process logical?
Thanks for any suggestions or insights into my problem.