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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
Comments: To: Darren <dfazio@BELLSOUTH.NET>
In-Reply-To:  <000801c272f8$c9cdd180$6501a8c0@Dell>
Content-Type: text/plain; charset="us-ascii"; format=flowed

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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