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Idle Switch Adjustment for 85-92 Vanagon.

February 3, 2015 10 Comments Fuel system Ken Wilford

Proper Idle Switch Adjustment

Many folks call me with the complaint that their Vanagon is not idling properly. Either they are idling too high or too low (stalling) or the idle isn’t steady. There can be several factors that contribute to this problem however most of the time the culprit is an out of adjustment idle switch on the throttle body. This switch is located below the throttle body on 85-92 Vanagons and most folks don’t even know that it exists. However if the computer is looking for a signal from it and is not seeing it, then it thinks it that the van is still driving down the road and not sitting at the light. I am going to give instructions for inspecting and adjusting this switch for 85-92 Vanagons.

Go to the rear of the van with the engine not running. Remove the engine lid and set it aside. At around the middle of the engine compartment you will see the throttle body attached to the metal air distributor for the intake. Use your fingers to move the throttle arm on the top of the throttle body from where it is at rest (idle position) to the full throttle position (as far as you can move it). Right when you are getting to the full throttle position you should hear a small “click” noise. Now slowly move the throttle arm back to idle position. Right before you get to this position you should hear the same small click. If you don’t hear it then the switch is out of adjustment. If you hear it then test the switch for continuity with a multimeter. It should have zero resistance at idle and full throttle position. If it doesn’t then you need a new one.

If you need to adjust the switch, the correct, Bentley way to do this is from above with a small allen tool. If you look straight down at the throttle body from above you will see a small metal plate with two allow screws in it. One of them is in a slot and the other is to the left of the slot. You want to use your allen tool to unlock the screw that is in the slot. Not use the same allen tool to turn the other screw to the left. You will see that as you turn it just slightly one way to the other the screw that is in the slot will move to the right or to the left. Usually, if your switch is out of adjustment, and you turn the screw so that the one in the slot moves to the left a bit, you will get to a point where you will hear a small clicking noise. Move it back and forth a few times until you get a consistent point where you can hear the clicking and then lock the screw that is in the slot at that point. Now move the throttle again several times from full throttle back to idle by hand. You should hear the click when at the idle position now. If not loosen the screw in the slot again and move it just a little more to the left and try again. What you are looking for is for the switch to click right at the idle position. You don’t want to adjust it too much so that it clicks before idle because then you will have a hesitation when taking off. This is the way to do it if everything is still in good condition.

However in the real world, many times you deal with the problem of someone messing with this switch before you, stripping out the allen head screws so that they are frozen and you can’t adjust them. Or they are just so corroded that they are melted and there is nothing for the tool to grab on to. If this is the case then you have to go to Plan B.

Plan B involves removing the intake boot and the two phillips head screws that hold the throttle body to the intake. Flip the throttle body upside down. Now you should see a black plastic cover that goes over the switch. Pull it off and set it aside. You will see the metal arm of the switch that rides up against the plastic cam that actuates the switch. The end of the arm is in the shape of a “U”. Use a pair of needle nose pliers and tweak the very end of the arm. You want to bend the part of the “U” that touches against the cam so that the “U” is just a little bit wider than it was (not a bunch, just a tweak). Now flip the switch over and try the test again. Tweak the “U” until the switch works properly at idle position. Now put everything back together and start the van. It should idle properly at around 950 rpms.

If you try to adjust your switch and it doesn’t click at all no matter what you do to it, most likely your switch itself is bad and needs to be replaced. You can also check it with an ohm meter to see if it is actually working electrically. You want to see “open” or infinite resistance when the switch is off idle and “closed” or very low resistance when the switch clicks at idle position and at full throttle position. To know what I am talking about, set your meter to ohms and just hold the two test leads apart. That is “open” so what ever your meter is reading at that point is what it should read at when the circuit is open. Now touch the two leads together. The meter may read zero or a very low resistance depending on how sensitive your meter is. That reading is what you should be looking for when the switch is closed or a very low ohm reading just above that. If it is reading hundreds or or thousands of ohms then the switch is bad. Do the readings a few times until you get some consistent readings.

Some folks try to work around idle control problems by raising the rpm or unplugging the idle stabilizer valve on the center of the engine. If you notice this valve unplugged, plug it back in. If the RPMS are still too high you might want to check your timing with a timing light. If the timing is on the money (7 degrees BTDC) then adjust your rpms down by turning the idle air screw (large slotted screw on the top of the throttle body) in a little. Count your turns so that you can put the screw back to where you had it originally if you find your real problem isn’t this screw.

If you are still having a problem with your idle after doing all of this then either your idle air stabilizer valve or the idle control unit is faulty. I would try cleaning the valve with carb cleaner and see if this helps. If not then swapping in a known good idle air valve or ISCU would be a great way to troubleshoot this problem. If known good ones aren’t available to borrow then you just need to flip a coin and decide which of these two expensive parts you want to try to replace first. Smell your ISCU (located behind the tail light on the passenger side on the 86-92 Vanagon). If it smells burnt then it probably is and needs to be replaced. I know they are expensive but having a properly functioning idle control circuit is important to keep your van running well, cut down on fuel usage, and keep the van from stalling when using the A/C or turning.

Idle Air Stabilizer Valve-
025906457AX
Idle Stabilizer Control Unit-
251907393D
Throttle Position Switch
025906011A

Copyright Van-Again 2015

Comments

RC de Mordaigle January 19, 2018

I had a similar issue in a 1988 2.1L manual trans. It would be driving along fine, then would start hesitating. Key off momentarily and then back on and it would run fine again, sometimes for a half hour or more. Accelerating from a stop, only when warm, it would buck, backfire run reluctantly. Ignition off momentarily and it would run normally. I bought a small wiring addition that replaces the end of the cable that goes to the air flow meter from GoWesty. Problem disappeared. VW made a similar part, NLA. But idle would not come down past 3k RPM when you lifted your foot from the accelerator. Disconnected the idle stabilizer and idle comes right down as it should. Accelerates fine from a stop, cold or warm. I'm leaving the idle stabilizer disconnected, as the idle is stable as it is. I'm thinking I should sacrifice a chicken under a full moon in front of the van to ward off any further mischief. So far, 350,000 miles, with half of that in the last three years. Engine recently rebuilt after a cam shaft bearing spun, came out and went into the valve lifters. These "Vanagon syndrome" issues are on both sides of the rebuild, with some occurring before and some after. All seem resolved now. Cruises well at 75 MPH, just at the CAlifornia Highway Patrol's edge of tolerance!

Ken Wilford September 6, 2017

That problem is usually caused by a malfunction in the oxygen sensor wiring or the oxygen sensor itself. Try unplugging the oxygen sensor and see if this helps. If not then you will have to test and repair the wiring of the oxygen sensor, since that is what is causing the problem. You may have other problems layered onto this one, but this is the main one. Let me know if I can help further. I actually talk about how to fix this problem in detail here on this forum. Just read what has been written and you should find your answer. Ken

Fosi Bear September 1, 2017

Hi Ken, thanks for your valuable help. I was following this thread and was happy to see your post about turning the engine off and "restarting" by dropping the clutch and without the use of the starter. This is exactly what I did just yesterday and had the same situation you described, restarted then 30-60 seconds later it would nearly "sputter out" and I would do it again. I was able to get home but was waiting for it to die out and not start up again. I had just put some gas into it just before this started to happened and first thought I had some bad gas or some water in the system. This was the first time it happened and did so while on a 3 hour trip trough the Rockies here in Canada and with the A/C on pretty full. I have a 1989 2.1L Vanagon with about 175,000 KMs on it. More info if needed can be posted. Thanks!

Ken Wilford August 24, 2017

Yes, it is most likely is the ISCU that has failed. It regulates the speed when the AC is turned on. I have rebuilt ones for $189 plus a $100 core charge. That should fix it. https://www.vanagain.com/shop/idle-stabilizer/

Tony Lo August 23, 2017

Hi Ken, Thanks for the valuable advice you have provided to the Vanagon community. I just got another problem with my van today. Everything was working fine until I turn on the A/C the engine idle suddenly surged up to 4,000 rpm and remains high until I turn it off then it comes back to normal idle. It never happened before. I checked everything related to idle adjustment and seems all right. I know the ICU regulates the idle speed when A/C is turned on, can it suddenly fail, or can it be something else? Thanks

Kevin Liddell April 21, 2017

I had a high idle problem with my 85 westy causing it to not pass California smog. This van only has 320k miles on it. No matter how I adjusted it I could not get the idle below 1000 rpm, took the throttle body off and compared it to another one and the gap around the butterfly plate was noticeably larger, replaced it and all is well.

Ken Wilford February 24, 2017

OK, let's try this first. When the van is running crappy, and you are driving down the road, turn the ignition key off and then turn it back on. You don't want to turn it to engage the starter, since you are still moving down the road, the van will just restart without the starter being used. Once you restart the van, does it run better for 30 seconds to a minute and then start messing up again? Or does it make no difference? Find out and let me know. Ken

uswagonvolks February 23, 2017

Hi, Ken - First, thanks for bringing me into the fold. I have an '85 1.9L digijet. (Its got about 175,000 on it for what it's worth. One engine rebuild in 2000. One tranny rebuild in 2008 for what it's worth.) I am indeed having an idle/stall situation. Same scenario every time. I'm going to list what I've done in best order. Problem is I cannot for the life of me recall when the idle/stall kicked in. I start cold. In day it runs evenly at idle ((about 940rpm and stays that way even (idle never wavers from 940rpms meaning I DO NOT have the problem of a few years ago of leaping up to 12, 1400epms then down up down but not stalling at idle)) when engine warms up enough to drop from 940rpms to sudden drop to 500rpms at a stop. It will pull back to 940rpms once then drop almost instantly again and either cut out or pull back up one more time. Naturally, I'm flicking the throttle, working the emergency brake to prevent stall when stuck at stop/start traffic. There's a notable weirdness that happens in the same place every time after it begins the warmed up idle/stall. I go through this gate. Then must drive 5mph along a stretch of about a quarter-mile. It goes into a godforsaken mode of extremely rough spitting, throaty, gravelly, choking, halting, hollowing out, begging me to let it stall until I get to my parking space at which point it will either instantly stall or not at all as if to mock my couple minutes of foot flicking to maintain idle. When I'm on highway from warmed up engine I feel this hollow on the acceleration which suddenly goes into acceleration increase lurch and seems to hang in that seeming normal acceleration modality from say about 40mph-60mph which I never penetrate higher. Usually it's 50-55mph. When I get off highway of course it goes into idle/stall again mocking my few peaceful minutes of normalcy in the consistency of above idle. I do have throttle click at low and high. I just did it two nights ago and believe there's the chance that on low end I move it a fraction of an inch before the low click happens. There's something about the motion of the Throttle that's thick from what I recall in the past years. This may be because I recently changed both CV Axles after what was a CV Boot leak on inboard passenger tranny side with cv grease spewage second only to Texas Chain Saw Massacre. You see, in my infinite wisdom I injected quite a lot of cv grease into the boot and taped the heck around that boot with silicone tape. Alas, a couple weeks later I reluctantly looked 'under there' and lo these many months I'm still finding cv grease spin out, even around the throttle body area. Recent work done by me and others working with me: With Gowesty Tune up kit: Changed spark plugs Changed spark plug wires (no positive click with or without the tops of plugs screwed off. Changed fuel filter Gowesty rotor does not fit my original distributor. Something tells me not to use Gowesty distributor cap after the no fit with rotor. (I have a metal shield over my distributor and know why it was oem that way. I choose to leave it for now until I get to bottom of this misfit) I changed ground wire on transmission. Sanded surfaces well I believe. Changed O2 sensor. Fairly sure the ground was well done. I'm about to run out of battery on laptop so will send this one and review for what else has been done or not done leading up to and during this idle/stall dilemma. I feel bad for my engine and exhaust because it has shaken terribly during this . I even think it caused a bit of an oil leak from shaking. I hope it heals. Thanks for input, Ken Not sure if the consistent wet conditions unusual for SoCal have some play in the "conductivity" or lack thereof.

Ken Wilford February 17, 2017

I guess I would have to see some pictures of the engine bay to know what to tell you on this one. That is because some later model European Vanagons (Transporter) actually used a tweaked version of the Digijet fuel injection system which used an idle air valve on the center of the engine like the Digifant version, however it used the digijet style idle stabilizer unit and a separate ignition module on the firewall over near the coil. These models may have had a plastic unit mounted behind the passenger side rear tail light that looks like a socket for the idle stabilizer control unit, however there would be no wires actually going to it and therefore it is just a dummy connector end that was never meant to have anything plugged into it. If you could send me some pictures I should be able to tell you what is up. Ken

Devon February 5, 2017

Hi; I've been driving a 1991 transporter for 18 years, brought to Jamaica from London (right hand drive), which did not have factory a/c. I have only recently discovered that it only has the idle stabilizer unit and not the idle control unit behind the right tail light. The socket for the ICU is present. My question is; can I install the ICU with the current idle stabilizer unit, or it's either one or the other. Thanks.

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