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Date:         Mon, 12 Oct 1998 22:14:25 -0500
Reply-To:     "John H. Rodgers" <inua@QUICKLINK.NET>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         "John H. Rodgers" <inua@QUICKLINK.NET>
Subject:      Update: Idle Speed Adjustment
Comments: To: Vanagon <Vanagon@VANAGON.COM>

-- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --

First, a thanks to all who have contributed to my efforts to get the idle speed adjusted on my '88 GL.

I got the job done, and want to share what I learned with the list.

1) The 1988 and later models have the Digifant Fuel injection systems.

2) The Bentley book is confusing as to how to adjust the idle speed.

3) There are two (2) Idle Stabilizer gizmos referenced in the Bentleys. They are not to be confused with each other, and if one pays attention, one realizes that they actually do have different names. So calling them by their proper names is important when conversing about Idle Adjustment.

4) Idle Stabilizer Control Valve - This is the solenoid gizmo on top of the intake air distributor on top of the engine. It is a solenoid operated valve that permits air(vacumn) to be pulled in up stream from the throttle valve directly into the air intake distributor. When cold it is held open and allows air to bypass the throttle body directly into the intake air distributor. I don't really know the purpose, but it ultimately results in smoother running at cold temperatures as in startup. After engine has warmed up, valve closes and shuts off air/vacumn. Now ALL air goes directly through the throttle valve.

To check the condition of this valve, allow the engine to be cold, as in the morning before starting it up for the day. Bentley says the valve should hum and/or vibrate. Mine does neither, yet works just fine.

Hit the switch and start the engine, run for a second or two, then shut it off. This allows the control unit to set the valve at the cold start position. With the engine off, remove the electrical connector on the end of the valve, and with a meter, test the two contacts on the end of the solenoid for continuity. No continuity means a faulty valve. Next, pull the valve loose from the small rubber tube/connector underneath and rotate it around far enough to be able to place your lips on the metal tube on the bottom. You should be able to draw air through the small metal tube. If not, the valve is faulty. Reinstall the valve, start the engine, and run until warm. With the valve is warm, go through the sucking procedure again. You should not be able to draw air through it. If it all checks out, and you still have problems, you may need to suspect the Idle Stabilizer Control Unit.

5) Idle Stabilizer Control Unit - This gizmo is a little black box located behind the right rear tail light You have to remove the tail-light to see it. There is a relay adapter (plug or board some would call it) with a cable attached to the bottom of it that is attached to the body in there and the Idle Stabilizer Control Unit is inserted from the top. This makes it possible to remove and re-install simply by pulling up on the unit. It allows you to be able to remove and install the unit blind, with one hand. There is no way to see what you are doing, unless you want to go to extra trouble. You just have to feel for it. The alternative, in addition to removing the tail-light, is to remove the accordian type air duct from the port in the side panel, then removing four fasteners holding the plastic side panel in place, then removing the side panel. With that done, you can see and perhaps work better on the Idle Stabilizer Unit. There is not much you can do for the Stabilizer Unit if it is faulty. Just remove and replace.

6) To adjust the idle,( this is not according to Bentley, but according to me in my experience), warm the engine. Then with engine off, disconnect the O2 sensor at the connector over on the left side of the engine compartment somewhere. It probably just hangs there. should be easy to trace from the O2 sensor plug in the exhaust pipes. Next, remove the connector on the end of the Idle Stabilizer Control Valve Solenoid. To do this, using thumb and forefinger, place the forefinger in the center of the circlip, and the thumb on the opposite side, and squeeze, pulling away from the solenoid at the same time. The connector should come right off. This instruction may sound simplistic, but I suspect that more than once that circlip and or connector has been ruined because someone didn't take the time to figure it out and tried to pry it off with a tool.

Start the engine. Let it stabilize for a minute, then adjust the idle speed using the large adjusting screw on the throttle housing. Turn the screw to the right to slow the engine rpm, turn it to the left to increase the rpm. In the standard vehicle configuration, you should be able to see the tach on the instrument panel as you make the adjustments. When you have it correct, stop the engine, and reconnect the O2 sensor, and the Idle Stabilizer Control Valve.

Next time you start the engine, hot or cold, the idle speed should remain pretty steady.

***************** If you want to adjust the CO, that is another story, best not told here for the moment in this long mail.

**************** All this is really simple, and it works, once you get into it. But when I began I didn't have a clue!!!! And it was all a bit scarey. But fact is, the injection system is really pretty straight forward. And I better understand my machine and can trouble shoot it better. And proper diagnosis is half the battle.

Good luck to all who try this.

John Rodger A happy '88 GL Driver tonight!!!!!

--


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