Poof of Exhaust smoke

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arearep@gmail.com - 05 Oct 2006 14:59 GMT

I was driving my '86 240 up a bill hill on the highway yesterday and
heard a few quiet knock and then noticed a one big poof of dark grey,
dirty smoke come out of the exhaust. I drove it about another half hour
back home on the highway and it didn't poof again. Any thoughts? It's
got abotu 200,000 miles on it. I haven't had any engine work on it
lately--just other things. It sat undriven for about 3 mos this summer
but I've been driving it regularly around town for the past 2 months.
Any suggestions? Thanks, Jan

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clay - 05 Oct 2006 16:59 GMT

> I was driving my '86 240 up a bill hill on the highway yesterday and
> heard a few quiet knock and then noticed a one big poof of dark grey,
[quoted text clipped - 4 lines]
> but I've been driving it regularly around town for the past 2 months.
> Any suggestions? Thanks, Jan

Sounds like an 'Italian tuneup'
Run it hard up a hill and the pinging knocks the carbon off the
combustion chamber resulting in the cloud of gray smoke.
Back in the '70's, the muscle car guys called it "kicking in the
afterburners" 'cause after cruising around all day lots of carbon built
up in the valves and heads. Then you ran it hard off a light and it left
a trail of gray like an F4 on burners.

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