Date:         Sun, 25 Feb 2001 11:57:13 EST
Reply-To:     CMathis227@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Chuck Mathis <CMathis227@AOL.COM>
Subject:      Warm Off Idle Stumble Part Two -- Some Improvement
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My '85 has been a bit cranky lately (even with a new exhaust system and O2
Sensor) so after consulting with the List, Bentley, the Bosch FI book, and
Darrell's website I tore into fixing various aspects of 'the problem.'

1) Replaced the cap and rotor -- there was some evidence of burning but not
bad.  The cap was the older style generic cheapo so I replaced it with the
newer style from Bus Depot.

2) Replaced the plug wires with a new Bosch set -- the old ones (surely not
factory) were tie-wrapped together and their cheesy red insulation had fused
in places.  Used plenty of dielectric grease on the connections and routed
the wires as far apart as I could get them.

3) Pulled the Bosch Platinium +4's and cleaned them -- a couple were a touch
looser and they all showed signs of running rich (probably built up before I
replaced the exhaust and O2 sensor).  Several folks argued that I should get
rid of the +4's but when I first put them in I got an immediate seat of the
pants power increase and my gas mileage increased a little.  Unless I eat the
motor in a way that can be directly attributed to the plugs I'll keep using
them.  I checked them for even gaps and torqued them in per Bentley.

4) Readjusted the throttle position switch -- I've got opening now right
about .021".

5) Replaced the Idle Stabilizer Unit -- this is the second time I've done
this and may not have been necessary so I saved the old one just in case.

6) Reset the idle speed and checked the timing.

Final result is a smoother running motor that still stumbles as it comes off
idle when it is warm.  When cold it flat takes off but warm it stumbles and
nearly stalls out unless I stomp the pedal hard enough to engage the throttle
position switch in the full throttle position.  When this happens the Temp II
is showing a steady .08 to .05 -- this seems to be the norm for this engine
after it has been driven a while.  The O2 Sensor reading at idle will jump
around from .70 to .19 until I apply a little pedal the the reading will drop
to
-0.001 to -0.003 then jump back into the normal range as the throttle
position switch reaches the full throttle position.

My two thoughts on this are 1) the engine might not be getting fuel quickly
enough (poor fuel pressure regulator?) or 2) the engine is gulping unmetered
air.  The reason for guessing #2 is when I looked at the AFM the bottom of
the throat where it attaches to the rubber boot looks like somebody dropped
it!  It is slightly deformed and may not be sealing all that well.  I'm going
to test this later with some duct tape.  If the duct tape experiment is
successful it may be semi-permanent until I can afford a new AFM -- this may
not be too far off anyway because the board looks much worse than the
pictures on the website.  I suspect the PO got ripped off by a bad shop.

Chuck
'85 Wolfsburg Westy -- 'Roland'