Date: Sun, 11 Oct 1998 11:55:06 +0200
Reply-To: Johan Nyberg <johan.nyberg@ABC.SE>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Johan Nyberg <johan.nyberg@ABC.SE>
Subject: Re: Idle stabilizer
Content-Type: text/plain; charset="us-ascii"
Hello list!
Malcolm, allow me to tell you that at least my '86 Caravelle has the Digijet, the air bypass valve AND the electronic timing advance idle stabilizers.
Per, I have exactly the same engine setup as you do. In fact, my idle is more stable when the stabilizer is disconnected. Have you checked the idle position switch on the throttle body? I fixed mine and a neighbour's van with bad idling behaviour by rebuilding this switch assembly and then do a PROPER idle adjustment. Even the people who installed his "rebuilt" engine only tweaked the idle adjustment screw until it seemed right. As this is a van with automatic transmission, it made things a bit involved. Also the temperature sensor in the thermostat housing influences idle, I think it's the blue one.
1000 rpm is a bit high for idle, my book says 800.
Here is my highly personal mental flowchart for dealing with idling, a Vanagon's, that is;-) I've only ever worked on the 2.1 litre Digijet DJ engine, but I believe most of it applies to the Digifant as well.
1. If it idles well, be happy and think of something else. My standard for idling "well" is that it starts happily cold or warm. That idle is a bit higher when cold than warm. With automatic tranny, the rpm shouldn't drop much when engaging "D". That it is possible to get going on reasonably even ground without touching the gas pedal. (This is my favourite trick for starting on ice or snow or slush or wet grass.)
2. OK, so if idle isn't to your liking, I'd start with checking the connections to the "DLS", the timing advance circuit in the little box of varying colour on the left in the engine compartment. Try pulling the plugs and connect them together. The DLS itself could be bad, or the connectors could be corroded. I've used WD-40 and pipe-cleaners and a lot of patience with good results. If the DLS is bad, just connect the plugs together and find a good one. In my experience, a bad DLS makes the engine very hard to start, but not much else.
Very important is check the throttle position switch. Test it for continuity with throttle fully closed and fully open. Quick check is to listen for the "click" when the switch opens or closes. If there is no "click", the plastic cam is probably worn or has dropped off or some other mechanical problem.
When you know that the switch is working, try to do a proper idle adjustment according to the repair manual of your choice. This means disconnect this, connect that, pull this and plug that. Different for different engines.
3. If idle is going violently up and down, I'd suspect the idle air bypass valve and/ or its controller. Check by "chinking" the rubber tube going from the air intake to that valve. If the idle goes back to normal, check, clean, replace, repair etc. valve and/or controller. It's in the archives. If the engine dies when the auxillary air is cut off, open the idle screw a little. It is possible to get an engine with bad throttle switch and/ or bad bypass air system to run quite decently by pulling the plug on the bypass valve and set the idle with the ordinary idle screw. This is useful while you are waiting for parts, or opportunity, or good wheather.
4. If idle is OK when the engine is cold but bad when hot, or vice versa, check/ replace the temperature sensor in the thermostat housing and make an idle adjustment per instructions.
I can't think of more at the moment. Hope it helps someone.
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Johan Nyberg, Sweden N 59o E 17o 25"
'86 Caravelle C
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