Date:         Thu, 17 Jun 2004 08:41:08 -0400
Reply-To:     Tim Demarest <tim.demarest@POBOX.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tim Demarest <tim.demarest@POBOX.COM>
Subject:      Re: Cold idle mystery
Content-type: text/plain; charset=us-ascii; format=flowed

If you've verified that the senders are OK, it may be a wiring issue.

- Sounds like your ECU is in 'warm' mode even when the engine is cold.

- Step one is to reseat all the electrical connectors in the engine bay,
sometimes you can isolate this kind of problem by wiggling connectors to
see if it changes the idle. Making sure the main connector to the ECU is
nice and tight can't hurt either, since all the sensor wires come together
right there.

- I assume you've already cleaned up the big ground connection on the left
side head, if not, do so!

- Also check the condition of the ground braid from that ground point to
the firewall. It's fairly cheap to double-up this connection with a second
ground braid.

- The most common failure point in the cold-start to warm-running
transiation seems to be the Temp Sensor II (water temp sensor, on the
thermostat housing). Sounds like you've verified that the sender is OK, so
make sure the connector is in good shape, and that the wires are well
crimped into the connector.

- There's also the Temp Sensor I (air temp sensor, inside the AFM), make
sure the connections to the AFM are nice and tight as well... this one
rarely seems to fail (based on reading various posts to this list), but
I've had similar cold start symptoms when I've forgotten to reconnect the
AFM connector after having the air box out.

- Vacuum lines are also real important! Make sure they are all tight and in
good condition. Twenty years takes it's toll, it may be a good idea to just
replace 'em all. My van came with a wide variety of dry rotted, loose or
collapsed vacuum hoses, most of which have been replaced now (ongoing
process, it doesn't seem possible to find *all* the sizes you need at any
one FLAPS... or two... or even three).

I've turned my '85 from a rough runner to a smooth one just by cleaning up
the big ground connection, adding a new ground braid, and replacing old
vacuum lines. It's cheap maintenance, and made a world of difference. I
hope yours is as simple a fix!


At 04:37 PM 6/16/2004 -0700, you wrote:
>Ok, time to put on your thinking caps.  Can anyone solve this by
>sheer brain power alone?
>
>Details:
>   1985 1.9l Westy w/Auto Trans and Air Conditioning
>   145k miles
>   Compression fair (around 120-125 each cylinder)
>   Recently replaced Digital Idle Stabilizer
>   Recently replaced AFM
>   Timing @ 5BTDC
>
>Symptoms:
>
>When warm runs fine.  Get 17-18mpg on the highway @ 65mph, so I don't
>think there is any gross mechanical problem with the engine or
>mis-tuning.
>
>When cold (60F), it starts right up, but quickly (either immediately,
>or within a minute or two) the idle is rough and the engine will die
>when in Drive, and sometimes even when in Neutral.   I have to keep
>one foot lightly on the accelerator to keep it from stalling.  Within
>about 10 minutes of driving, the problem goes away.
>
>I've tried setting the idle higher when cold (with a few turns of the
>idle adjustment screw).  This solves the stalling problem when cold,
>but then when the van is warm, the idle is way too high (1500+ rpm).
>
>I've gone through the Bently and done most of the electrical digijet
>diagnostics  (resistances of temp senders when cold and hot, etc.)
>without finding anything amiss.
>
>Ideas?

Tim Demarest
tim.demarest@pobox.com