Date: Sun, 13 Oct 2002 15:02:30 -0700
Reply-To: Doktor Tim <doktortim@ROCKISLAND.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Doktor Tim <doktortim@ROCKISLAND.COM>
Subject: Re: Excessive Idle
In-Reply-To: <000801c272f8$c9cdd180$6501a8c0@Dell>
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Have you verified timing and mixture??? Try that first. Either over
advanced timing and/or rich mixture could cause the high idle. Verify per
Bentley procedure.
At 01:40 PM 10/13/2002, you wrote:
> My '87 is idling around 2000 rpm with the engine warm. The idle adj
>screw is all the way in and I don't believe I have any vacuum or exhaust
>leaks.
What you don't believe is out of context with the real world. You must
prove you have no vacuum or exhaust leaks. For vacuum leak testing see the
archives, "Deutsches Methode, Vakuum Schlucks". For exhaust leaks, you can
run your finger within a half inch around flanges and pipes and feel quite
a small puff and not get burned. Look for black carbon traces with the
eye/light tech. Watch out for the belts, though, very tricky for the rear
ports if you're the least bit concerned about finger losses.
Then, listen to the idle control valve, (if memory serves you have one on
the 87) round and some 120 mm long and 40 mm diameter with two hoses of
12+mm diameter and an electric connector vicinity top/center of the motor
or low right side of the intake plenum. The hoses run from the intake
plenum to the idle motor to the intake duct. Looks like a little electric
motor, cause that's what it is. At idle, it should be smoooth and quiet.
This motor does not spin but fluctuated back and forth, opening and closing
an air valve very quickly. One that is sticking or not getting juice can
cause your symptom. But typically this is a progressive disease of the
points wearing grooves into the commutator in the motor. It will start to
stick occasionally, infrequently, then over the course of several weeks or
months gets worse and worse, but they can go quickly sometimes.
If no noise or hum, check for voltage and ground at the connector, or open
or short through the armature. If no voltage, suspect the idle control
computer or it's 12 volt feed or ground. The more you press these type idle
motors past 150k, the faster you approach a problems where it begins to
draw more amps than designed and can fry the control box, so if it's a high
mileage original, replace it now and either fix the problem or find the
source elsewhere. All I have replaced have been typically 120K to 200K.
If you have the earlier disc type bypass valve, under the no. 1 intake
runner, pull it off and put it in the freezer for half and hour. Look
through it, the valve should be fully open. Put 12 volts to the terminals
and watch the valve slowly close as it warms up. might take 3 minutes for
it to completely close. If this is the kind you have, it could be stuck
open. It should be getting 12 volts whenever the key is on.
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