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Backfiring

To: "healeylist" <healeys@autox.team.net>
Subject: Backfiring
From: "Bob Spidell" <bspidell@pacbell.net>
Date: Wed, 5 May 2004 06:20:44 -0700
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
********************************************
Bob Spidell         San Jose, CA        bspidell@pacbell.net
'67 Austin-Healey 3000             '56 Austin-Healey 100M
********************************************





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