Dave, Dion, Joe & the rest,
Thanks again for all the responses, I had never considered the muffler or
exhaust system. The muffler looks fine from the outside, but who knows? It's
worth a try. The funny thing, is that the truck coughs and sputters and won't
run, then it will take a notion to run just fine for a few miles, before it
decides to shut down again. Indicating somewhat of an intermittent problem.
When it does decide to operate, I can be going down the highway as smooth as you
please then suddenly the truck will start bucking (as if it were only getting
spurts of gas), and loose power. So much so that I will be forced to pull over
and keep pumping the accelerator until it will go again. Sometimes it decides
not to cooperate and I will end up having to tow it home.
However,the actual down time has by far exceeded that of the up time, during the
previous 500 "or so", miles that I have been able to drive it over the last
couple of years.
I will also check into the stuck valve idea, but wouldn't that be an
intermittent problem, based on the "on / off" operation of the motor?
I have checked the timing with a timing light and everything appears to be in
order. I have never had the distributor out so I am assuming that it should
still be in the correct position, unless it is driven by the camshaft and that
has slipped. But then wouldn't that be evident when checking the timing with a
light?
As for the timing belt, it feels tight, but who knows, at about 81,000 miles it
is still the factory installed belt. Just because the distributor still fires in
sync with the crankshaft, doesn't necessarily imply that the camshaft is still
in the correct position, or does it?
The thing that bugs me, is those times when it decides to operate correctly. My
experience with timing belts has been that once they go out it is not likely
that they will slip back in (on their own), for a hundred miles or so before
jumping back out of time.
Although, on the Fiat Spider, I have been known to reset them myself (when one
has slipped), and re-tighten'd the tension just to get me through until I could
get a replacement. I am again assuming that the mechanics are the same.
Thanks again,
Satellite Steve
Clips from various responses:
>I would seperate the exhaust at the front of the cat. That way both >the cat
and muffler are out of the loop.
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>The truck had around 90,000 miles and the muffler was'nt looking to >good so my
Dad changed it and low and behold it ran great.
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>We were about to give up when I noticed the exhaust manifold had >turned cherry
red. We had run it like this for about 5 minutes. We >immediately shut it down.
>If the exhaust manifold becomes cherry red, the spark is firing too >late
relative to the valvetrain (or a valve is stuck - compression >test will show
that though). Either the timing is off or the cam is >not timed with the crank
properly.
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