climbing idle

Microbusdeluxe · Posted: Thu Apr 23, 2009 2:19 pm Post subject: climbing idle

'81 California ignition aircooled Westy, manual trans. Starts easily, runs great, pulls strong (for 67 thundering hp). Does get crappy gas mileage (12 mpg around town). Tuned up, no help.

Problem is after a couple of minutes the idle will slowly increase to about 2000-2500rpm (no tach but I've got the time!). If I shut it off, I hear a click, restart and idle is nice and smooth at proper rpms. It does not hunt/rove around like a vacuum leak. After full warm up (20 miles) it usually goes away.

Thought it was a hanging up accelerator cable, but it's not. Clues??

Microbusdeluxe · Posted: Sat Apr 25, 2009 6:07 pm Post subject:

I'm bringing this back up to the top in hopes of getting some advice. If that doesn't work I'm gonna retitle it "Naked women" or something to get me some attention!!

jcrofford · Posted: Sat Apr 25, 2009 6:18 pm Post subject:

Idle Stabilizing Unit (ISV?)? Supposed to control idle. There are checks for this in Bentley, but I don't remember specifics off hand.
Maybe...
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'83 AirCooled Vanagon L, CA

Randy in Maine · Posted: Sun Apr 26, 2009 5:12 am Post subject:

Is this a Federal set up or a CA one?

I would start by looking for a vacuum leak. The S boot and anything going to it (like the AAR) or coming from it are likely suspects as is the brake booster side or the air plenum.

Duct tape, some corks, "shoe goo" for the S boot, and Gum Out carb cleaner are your friends here.

Keep in mind that vacuum leaks = lean running = hot cylinder head temperatures = dropped valve seats

When was the last time you did a proper compression test or a leakdown test to see what you have? If you are not going to do it correctly, take it to a shop and have it done.

Microbusdeluxe · Posted: Mon Apr 27, 2009 12:25 pm Post subject:

My 81 is California emissions. Compression is fine, recently checked. While I haven't done a leak down test I have pulled off a vacuum line as it is running, which causes the revs to climb and hunt around. That is not the problem, the idle is smooth, there is no backfiring or hesitations just this maddening and occasional increase in the engine speed as I sit at a traffic light.

Yesterday we took it for a long drive, it did the climbing idle thing, then it didn't. Pulling into the house (engine nice and warm) it did it again, high revs. I shut down the engine, heard a loud "click" then restarted it. Idle was spot on about 800 rpm. I then shut it off again and there was NO CLICK sound. So I'm thinking the problem is not a vacuum leak but something electrical that's tripping when the power is shut off.

Thanks for your input, but I don't think we're at a solution yet.

RCB · Posted: Mon Apr 27, 2009 1:00 pm Post subject:

I had this exact same problem...drive awhile on the freeway and when I got off the exit and came to a stop sign the idle would go crazy high.
I replaced the decelleration valve and no more problem..

Microbusdeluxe · Posted: Tue Apr 28, 2009 4:45 pm Post subject:

I've got a NOS deceleration valve coming to me, fingers crossed, I'll post results, thanks for the input.


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