Bob, my BT7 started to do the same. My mechanic told me that this kind of
backfiring is caused by an exhaust leak. You may want to check your exhaust
pipe by letting the engine idle and at the same time partially close the end
pipes by pressing some kind of cloth on it. Watch if any fumes disappear from
the pipes where they shouldn't.
Good luck.
Eric BT7
Heinsberg, Germany
Listers,
My BJ8 has started making fairly loud popping noises through the exhaust
recently. This occurs mainly when coasting downhill in gear, doing a little
engine braking, but also happens sometimes after a downshift on the flat
(always under closed throttle). I supporse it's not actually a backfire, a
singular, random "bang," but a series of moderately loud popping noises in
the exhaust.
I didn't change a thing--it was running perfectly--this started about a
month ago. I tried both leaning and enrichening the mixture with little or
no apparent effect.
The only thing I can think of is the new, summer CA gas formulations.
I believe we're getting up to 20% ethanol mixture now, with no more MTBE.
I'm wondering if this gas is causing the backfiring due to differing vapor
pressure
or something. Anybody know what else could cause this?
bs
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Bob Spidell San Jose, CA bspidell@pacbell.net
'67 Austin-Healey 3000 '56 Austin-Healey 100M
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