Vanagon Engine Surging when in Idle ..... SOLVED

[zoti]

[djkeev]

[HackAl]

Zoti, Dave, thanks for the replies.

Just drove it 100 miles home with the IAC disconnected and no issues.

This is what I bought: https://www.busdepot.com/025906457a

Not returnable apparently, but why would this cause unexpected revving and high idle unless it was defective?

I'll plug my old one back in tomorrow and see what happens. Again, the only reason I replaced it is because I thought it might solve my occasional stalling problem when the van sits for a while.

I may just change the oxygen sensor for good measure if I can easily get it out.
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91 Westy.

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[Wildthings]

[zoti]

[HackAl]

Thanks. I found somebody in Oregon on the Samba selling a rebuilt idle control unit for $180. I reached out.

Just to be clear, my idle returned to normal when I unplugged the IAC. I did not have this problem with my stock IAC.
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91 Westy.

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[4Gears4Tires]

I'm waiting on Zoti's new IAC control module. Needs to be out sooner.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[Wildthings]

[HackAl]

I'll go back and see if the new IAC vibrates, I don't believe the old one did. However, when I hooked up the connectors to a 12v battery, I could clearly hear the valve open and shut (on the old one).

I'm inclined to try a new control unit to rule it out, though I hate chasing a problem with parts I can't return.
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91 Westy.

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[HackAl]

Seeing a very similar fact pattern in this FB thread which I am studying now: https://www.facebook.com/groups/vanagontech/permalink/1611624529014451/
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91 Westy.

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[HackAl]

So this is probably a lesson in "leave well enough alone" . I just set out to solve the issue where the van occasionally stalls at cold startup.

I got my hands on a rebuilt control module from a Samba user for $260, with $100 back when I return the core. I tried that with the recently purchased idle air control valve from bus depot which I think is defective. When the new IAC is connected, the idle runs high and fluctuates. This happens with both control modules.

I put both my stock control module and IAC back in and I will live with that for now. Wondering what I should do with these two parts now. I may return the module and just get my core deposit back but I will be eating $160 plus the $125 for the IAC, which is not returnable as an electric part.

Thoughts? Thanks.
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91 Westy.

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[Wildthings]

If you are getting different results with different parts then one or more parts are not operating as per the book. Maybe try to find someone with a Vanagon with the same FI system and use his parts to see it that makes it work correctly.

I know when I was first trying to get my '87 Syncro to run correctly I changed out every part of the FI and Ignition systems with my '91 without solving the problem excepting the spark plug wires as they were obviously almost brand new and ohmed out fine. When I finally changed out the wires the engine ran perfectly, apparently there was something in the inductance of the wires that messed up the ECU somehow. The moral of the story is some minor glitz that you wouldn't think could have an effect can mess up other parts of the FI system.

[HackAl]

Thanks Wildthings. Agree with everything you said.

But the plot thickens. I just blew into both the original and replacement IAC. On the old IAC, I cannot blow through it all when the valve is closed (with the spring piston extended inside). On the new one, the piston does not close all the way and a little air gets through,- which I'm assuming is what is causing high idle with the new IAC.

The new IAC is made by Lowe automobil. Does anybody have any experience with this part or brand? Will contact Bus Depot and see what they say.

It's still not clear to me whether there is anything wrong with my original IAC but I can't rule it out relying on a defective part to diagnose. Very few van owners within 50 mi of me, so I can't swap it out with one I know works.

Using my meter, I get continuity on both units.
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91 Westy.

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[HackAl]

10 minutes after my last post I discovered that I am a bit of a dumbass. Apparently when I changed my plugs and wires a couple months ago, I had not adequately secured the air cleaner filter housing. The c-clamp was not tight and air was apparently getting into the system. I'm sure that was contributing to the problem somehow. But the new IAC is still defective as far as I can tell. I contacted Bus Depot and will let you know what they say.

But my old IAC may have been working just fine. Air was just getting at the c-clamp connection. That's my new hypothesis anyway.
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91 Westy.

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[HackAl]

As far as parts, I was able to return the module without issue. And it turns out that Bus Depot got a few defective IAC valves and will let me return that too.
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