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
-- [ 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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