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

[TAJ56]

I am the new owner of a 1990 Vanagon Westfalia camper. I bought the van in northern California. The first day I drove it to Bend, OR and the following day to Port Townsend, WA.

On the first day, the engine idled normally. On the second day, I noticed that when I was stopped and the engine was idling, it repeatedly surged up and down. When I put it in gear and drove it, the engine did not continue to surge. But, when it was in neutral it did resume surging up and down.

I informally asked a local mechanic who commented that sometimes engines "get used to" a certain elevation and when they are relocated to a different elevation that this surging could occur. The van had been housed at an elevation of 3,500 feet. My second day of driving I crossed a pass over 5,000 feet. I live at sea level.

Has anyone ever heard of the elevation impacting the idling of an engine?
Does anyone have an idea of what the issue might be and how to correct it?
Thanks.

[Merian]

may be in the FAQ, if not the best search term is hunting idle (not surging)

several things can cause this so do the easiest & cheapest first
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[Ahwahnee]

[raoul mitgong]

Tough to diagnose online but some $0 places to start would be:
-Clean all grounds. Two star grounds behind fuse panel and all you can find in engine bay.
-Check for cracks or loose clamps in rubber boot from AFM (downstream from air filter)
-Check for proper adjustment of idle switch on throttle body (directions found on this site or Bentley manual).
-Run a bottle of injector cleaner through a full tank (not $0 but close enough)

Welcome to the madness! Now let's see some pictures of your new ride!

-d
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84 Westy with a 2.1 (Groover)
86 Tintop Syncro (Crow)
86 Tintop Syncro to Westy project (Tom Servo)
91 Westy (Only the top 12 inches of this van (a burn victim))

[Selsk]

Possibly the MAF sensor?

http://www.gowesty.com/product-details.php?id=23992

I second the injector cleaner...it helped calm my idle.

[Wildthings]

Adding the Vanagon Syndrome capacitor can help with obtaining a smooth idle. You may have some kind of a vacuum leak which is throwing the idle mixture off so check all your vacuum hoses, boots, and elbows over carefully. Just replacing them all and getting it all over at once is a good way to go.

I would third the use of FI cleaner.

[E1]

Vacuum leak is what I always think when this happens. In our case, it'll do it a day or so, then completely disappear for weeks or months.

My theory is it takes in too much air suddenly but hasn't enough fuel, so leans out until the mixture catches up.

It's just a theory, but it used to do it all the time until I replaced my vacuum lines. One would think the O2 sensor would negate my theory, but in our case it seems it happens faster than the sensor can adjust for.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[TAJ56]

Thanks everyone for your observations and suggestions. I'll post a note when I've got it resolved.

[danfromsyr]

anyone ever check that the diaphragm in the evaporative valve hidden behind the PS firewall/wheel well isn't ruptured and loosing a vac signal?

how tight and crisp is the throttle plate in the throttle body, if it's getting loose and sloppy it'll cause idle issues.
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[E1]

Do you mean the Space Needle-looking thingamabob just in front of the airbox?

(sorry to speak so technically)
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[danfromsyr]

yeah,

the bay bus crowd have on occasion had issues with theirs.. though the bay is easier to get ahold of.

image swiped from the internets.
http://subaruvanagon.com/tom/Getting%20Started/EB-R%20cc%20canister%20&vac%20valve%20sm.jpg
[img]http://subaruvanagon.com/tom/Getting%20Started/EB-R%20cc%20canister%20&vac%20valve%20sm.jpg[/img]

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[Merian]

rather than just use FI cleaner, if there are many miles I'd send the injectors out for a proper cleaning as it needs to be done as Long Term Maintenance anyway
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[E1]

[danfromsyr]

suck on the vacuum line and if there's no resistance then the diaphragm is busted.. all I know is it happens with the Bay guys on occasion and throws off some engine management.
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[E1]

Thanks Dan.

If I breathe or blow through the top line, it has some draw but not as if there's no resistance. Maybe half of what an open line would have.

When breathing through the bottom line, whether in or out it's almost entirely resistance -- as if clogged or valved regardless of direction.

Edit: Meaning, I'm not sure if the diapragm controls the top or bottom inlet, and what direction of vacuum is correct on both of the inlets.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[danfromsyr]

my understanding of the valve would be that
when vacuum is drawn on the small nipple
that the 2 larger ports would be open to each other..
ie. a Normally closed relay.

if the diaphragm is broken.
you would be able to draw all the free air you wanted from the small nipple.
or blow into/thru either of the larger ports and air escape out the little nipple.

not saying it's your problem, but it's not on the normal vanagon problem checklists. and I have to check mine on my new to me van re: an idle stumble..
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[E1]

Yep, mine's clogged on the bottom (larger) port. Sounds like toast.

Thanks for that! Shop replacing our oil breather tower said it wasn't working anyway, so re-routed the vac line directly to the front-side engine port, instead of to the T and then to the charcoal filter valve. They called the valve an "inconsequential California smog thing."

I've routed it back as an original T setup, we'll see if that hurts on next fire up. Van runs very good but not as snappy as a couple months ago, so always on a mission.

Appreciate it, Dan.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[TAJ56]

Folks, thanks for all your suggestions and input. It turned out to be the oxygen sensor. The engine surging/hunting/loping ended immediately after replacing it. By the way, I learned you can get the oxygen sensor on Amazon for quite a bit less than on Go Westy or Van-Café.

[HackAl]

Having the same issue on the road right now and don't really have too much ability to research. Is the oxygen sensor something that I can easily replace with basic tools? how do I get to it?

I had also recently replaced my IAC and disconnected it and the problem has not happened again. I'm wondering if the new IAC may be defective.
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91 Westy.

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[HackAl]

When I plug the IAC back in, I noticed my idle was around 1500 RPM. Usually 900. As soon as I unplugged it, idle was normal again.

This is leading me to suspect that the new IAC that I purchased from Bus Depot is the culprit. I replaced my stock IAC in the hopes that it would solve the occasional stalling that happens when the van sits unused for a while.

I understand that my oscillating, unexpected revving could be associated with a vacuum leak. Does anybody suspect that the IAC could have somehow caused the unexpected revving issue?
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