Date: Wed, 6 Nov 2002 23:48:19 -0600
Reply-To: John Rodgers <j_rodgers@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <j_rodgers@CHARTER.NET>
Subject: Re: ISV questions (updates and clarifications)
Content-Type: text/plain; charset=us-ascii; format=flowed
Roger, it sounds like you still have a problem with that idle stabilizer
circuit, and in all likely hood the valve itself. The ECU takes the ISV
out tog the loop when the engine warms up, so it should idle @1000 or so
when cold, and when warm idle at 850-900. When you manually disconnect
the ISV you have done what the ECU would do when the engine warms up..
If the ISV is disconnected or inoperative, when the engine is cold
turning the steering wheel will nearly always kill the engine. When the
AC is turned on, the engine RPM will jump significantly. If there is
something wrong with the ISV circuit, the rpms could jumpo righ up there
quite high.
Hope this helps in the understanding.
John Rodgers
88 GL Driver.
Roger Reynolds wrote:
> Hi all,
>
> I have been trying to track down a high idle situation for some time now and
> still have had no luck.
>
> The problem is a high idle (around 2000) that starts a couple of minutes
> after start up. If I disconnect the ISV connector, even briefly, while the
> engine is running at high idle, the idle will drop down to 900 RPMs and stay
> there for as long as the engine is
> running. If I restart with the ISV connected, the idle returns to 2000. The
> idle will kick up to 2400 when I turn on the AC and return to 2000 when I
> turn it off. I have also noticed that the engine will often stall soon after
> it is started (it idles lowish (800-900) right after start up).
>
> Update: The idle was not kicking up when I turned the steering wheel all the
> way to one side so I jumpered the wires leading to the power steering
> pressure switch and the RPMs did kick up from 2000 to 2400 so I'll replace
> the power steering switch. That could be why it has been stalling in the
> mornings (as I'm backing up and turning) before the high idle starts.
>
> According to Bentley, the ISV should "vibrate and hum" when the ignition is
> switched on. My valve will vibrate and hum for about three seconds after the
> switch is turned on (without starting engine) then stop. I have noticed that
> when the engine stalls and I'm at the engine compartment, I can hear the ISV
> hum for a few seconds then stop. When the engine is running at 2000 RPMs, I
> can't tell if the ISV is humming or not because of all of the engine noise.
>
> Bentley says the resistance across the ISV should be: continuity, mine is 4.5
> ohms. Is this good enough?
>
> I have performed all of the tests, that Bentley lists, at the ECU connector
> and everything is within specs given. Have replaced: the idle stabilizer
> control unit, temp II sensor, spark plugs, plug wires, and O2 sensor. I have
> also: cleaned the AFM, measured AFM resistance values, looked for vacuum
> leaks, cleaned the grounds to the
> left inside the engine compartment, adjusted the idle setting, and checked
> the throttle position switch.
>
> Update: When I pull the yellow idle stabilizer control valve connector (that
> is located sort of above the thermostat housing) apart the idle drops to
> around 1000 RPMs. The thing that doesn't make sense to me though is that I
> can't get a current value at all (0 mA) when I connect my DMM in series
> between the terminals of this connector. I was expecting to get 420 mA.
> But, when the DMM is connected to the two terminals, the RPMs surge back up
> to 2000. If I switch over to read voltage between the two terminals of the
> connector, I get around 7vdc.
> Looking at the Bently manual again though, I think it is saying that I have
> to first remove the crankcase breather hose. I'll try that and see what
> happens.
>
> Any advice would be greatly appreciated.
>
> Roger
>
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