Date:         Sun, 21 May 2006 19:29:49 -0700
Reply-To:     Michael Diehr <md03@XOCHI.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Diehr <md03@XOCHI.COM>
Subject:      Re: FrontFire?
In-Reply-To:  <446799B7.3080206@verizon.net>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

An update.   Mechanic did the 500 mile check, put in a new O2 sensor
(the old one had external damage, and had been in the old engine when
it died).   I went to pick it up from the shop, started it up, it ran
great, no more "pop/squeak" noise.  Drove about 2 blocks away, then
suddenly the idle dropped to about 400 and it began making that
horrible noise again.  Took it back to the shop right away, and
fortunately the mechanic was there and could hear the noise (though
by then the idle was no longer dropping).   After some poking around
in the engine bay, we discovered that the noise was simply the sound
of the airbox banging on the right side wall of the engine
compartment, as it totally went away if you gave a gentle pull.  The
noise only came about when the engine idle was dropping too low, and
the engine was bouncing around a bit.   Instead of causing the low
idle, the sound was the result of the low idle.  Bizarre.

 From a cold start, the low idle only seems to happen after about 1-2
minutes, then goes away after about 5 minutes.    So I'm guessing it
may be a problem with the thermo-metallic idle bypass thingy (the
tube that is normally open when cold, but closes as the engine warms
up?)




> Ok, more info here.
>
> To recap -- an 85 westy with a rebuilt motor with about 500 miles on
> the rebuild.  Immediately post rebuild, it would idles somewhat
> roughly, smelled like it was running rich, poor fuel economy.
> Drove it around for about 500 miles, then I took it to a different
> mechanic who did oil change and adjusted the richness, after which
> point it smells less rich, gets better freeway mileage, but idles
> very poorly including intermittent loud "pop" noises as if one of the
> cylinders is "frontfiring" up the intake pathway. Also has trouble
> keeping the idle speed up when in gear (auto tranny).
>
> Most of the FI system is new/rebuilt:  Distributor, wires, cap &
> rotor, AFM, vacuum hoses, idle stabilizer, and even a new (used) ECU.
>
> Today, I disconnected the O2 sensor, and like magic everything
> improves dramatically -- absolutely no more "pop" / frontfire noise,
> idle is much smoother.  It does smell a bit rich at idle.  Power on
> the freeway seems about the same.
>
> My dilemma -- do I assume this is all the result of a flaky O2
> sensor, and just fix it myself or have a local shop do it, or is it
> still possible something is seriously wrong with the engine (sticking/
> broken/misadjusted intake valve) and take it back to the shop that
> did the rebuild?
>
> To add to the decision complexity, it's about an hour drive each way
> to the mechanic that did the rebuild, and I'm moving permanently out
> of the area in a week...