I'm posting this for a friend. The truck is a 93 4x4 club, auto, V8
with
about 80,000 miles. Everything is stock. Recently it has developed a
heavy
knock, but it is intermittent. Doesn't have to be under load to knock.
He's tried high octane fuel, it doesn't help, there are no computer
codes
generated (will knock on 92).
Ideas guys? Feel free to email me directly and I will pass your ideas
on.
Thanks much.
Rob Agnew
ragnew@islandnet.com
Victoria, B.C.
Canada
------
Rob,
You probably want to get a timing light and check the timing up to about
3,500. Incorrect ignition timing will cause that.
Also it could be carbon build up on the top of a piston. It can build
up so thick as to increase the compression ratio and cause spark knock.
I've also seen it on a Chevy build up so bad that it was slapping the
head and sounded like a spun rod bearing. We pulled the motor out and
found nothing more than some clumps of carbon on the pistons and a mark
on the number 5 chamber that showed where it was hitting.
The poor man's remedy used to be to pour a little water in the carb, or
throttle body while revving it up to about 2500 or so. The engine will
cough and sputter, but hopefully the cold water will knock the carbon
loose.
Good luck, Drew.
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