Date:         Wed, 8 Aug 2001 15:05:32 -0500
Reply-To:     "John Y. Hung" <jdaezhung@HOME.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "John Y. Hung" <jdaezhung@HOME.COM>
Subject:      Re: Van dying once warmed up; FI motor
In-Reply-To:  <200108080403.f7843nb18628@mx14-tx.mail.home.com>
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

Hi all,

Regarding the '82 Vanagon that dies when warmed up.  Some things to check:

1.  The auxiliary air valve allows some intake air to bypass the
throttle valve when the engine is cold. The extra air is sensed by
the air flow meter, and processed by the computer, so additional fuel
is injected.  The net result is that the idle speed is higher when
the engine is cold.  The auxiliary air valve should close off,
however, once the engine is warmed up, and idle speed should return
to normal.  If the valve is stuck open, the idle speed will be too
high.  One can jury rig a fix by adjusting the air bypass screw at
the throttle, but that is not a good long term solution, and doesn't
always work.

2.  A fifth fuel injector on the intake manifold is also found on
some Vanagons. This injector supplies additional fuel to help start a
cold engine.  The valve is also controlled from thermal information.
If the valve is leaking or the control is not shutting off, the
engine will run rich.  Mileage will be poor, and hot starting may be
a problem (flooding).  The smell of raw gas may be present, but only
in extreme cases.  Leaky cylinder injectors can also be a problem.
Bentley's manual has the procedure for checking these.  I've yet to
exerience a bad injector in 14 years of Vanagon ownership, but they
are not difficult to check.

3.  In my experience, most fuel injection system problems are due to
poor sensor information given to the computer.  I believe the
computer itself is quite reliable.  On my Vanagon, there is a coolant
temperature sensor, air temperature sensor, air flow sensor, O2
sensor, and several switches to check.  On most Vanagons, almost the
entire fuel injection system wiring can be checked out at the
computer connector.  Get a volt-ohmmeter with thin probe tips.
Bentley's manual gives all of the voltage and resistance specs.  Most
problems can be solved by cleaning terminal connectors.  Poor ground
connections have been common on my vehicles.  They seem to be prone
to corrosion, being exposed to the elements.  The other connectors
usually have rubber boots on them.

4.  Finally, don't forget checking the ignition system.  Timing is
pretty much automatically controlled, but leaky vacuum lines can
result in poor performance.

Happy troubleshooting.  There's no greater satisfaction (and at times
frustration) than keeping one of these vehicles in good running order.

Sincerely,

John Hung
Auburn, AL
'84 GL (had a hot-start problem last week - bad ground connection)