Sticky high idle issues

[Slimvest]

'87 manual w/ 2.2 wbx.

I've been dealing with sticky idle over about a year and half. It originally was mostly when the van was cold, but has transitioned to all temps as of late.

I'll start the van cold and it idles up a bit to 1500 or so, then eventually settles to 950/1k. Once I start driving, the idle won't drop between shifts very consistently or it's very slow to do so. I feel it sticking when letting off the gas too, leading to a lack of proper deceleration.

Backstory:
July 2017. After having some trouble with emissions testing, I replaced my throttle body with a new one from GW in hopes of being able to tune my idle a little better. It seemed to work well, I passed, but I began to notice the cold start idle issues as soon as the weather started to get cold in the NW. As I said above, it's now transitioned to warm operating temps. Assumed it was the TPS and have tried adjusting it multiple times. It does click in both positions.

I swapped in a good ISCU too and still have the same symptoms. The idle control valve has power, vibrates with key in the on position, and the motor will drop in idle if it's unplugged. I haven't tried driving with the valve unplugged yet. I could try backing out the idle screw on the TB, but then I'll be left with a higher than normal idle. (GW suggested this)

What am I missing?
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'87 GL w/ Reimo top

[Howesight]

Besides the Vanagon, many other Volkswagen and Audi vehicles from the early 1980's right to the late 1990's used the vibrating Idle Stabilizer Valve system. Those valves do wear out and then cease doing their job properly. They contain a solenoid that rapidly opens and closes a path for the idle air. When they wear mechanically, they stick, often open, and sometimes on the shut side.

I have stretched the life of them in some instances by cleaning and then lubricating with "Moovit" brand penetrating oil or WD-40 (which is less effective), but this tends in most cases to be a temporary fix.

The idle stabilizer control unit and its wiring can sometimes cause the kinds of symptoms you have, but more frequently, the ISV itself is the problem.
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'86 Syncro Westy SVX

[Slimvest]

Thanks, Howesight. I blasted some carb cleaner into the valve last night, but haven't taken it for a drive yet. Will do so tonight.

Conveniently (not), a friend was visiting from Hawaii whose ICV failed on him. I thought I'd be a nice guy and give him my spare. Three weeks later, mine seems to be on the way out. Wife says, "I told you not to give that to him!"
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'87 GL w/ Reimo top

[Zeitgeist 13]

You should blast some lubricant in there before reinstalling.
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Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[Howesight]

A Samba member, Tencentlife, who knows a lot more than I ever will about the WBX engine, posted on sticky idle control valves a long time ago in this helpful thread:

https://www.thesamba.com/vw/forum/viewtopic.php?t=338699
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'86 Syncro Westy SVX

[MarkWard]

If the accel cable/ linkage is hanging up, that should be easy to isolate. When the engine idle is high, go back and see if the throttle plate is against the idle stop.

I'm not familiar with the GW throttle body, but on digifant systems, the idle switch adjustment is very particular.

It's also possible your base idle is set just at the edge of what the idle system can control.
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☮️

[Slimvest]

[MarkWard]

If the throttle plate is on the stop, its not the cable etc. I'd look at the manual for adjusting the idle switch on the throttle body. The method is probably different with the GW unit, but it's still critical for the ECU to know when and when not the throttle is closed.
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[Slimvest]

It was the idle control/stabilization valve sticking. Took it for a drive last night and the idle would drop off a lot quicker when shifting between gears and deceleration was also a lot better.

Carb cleaner fixed it and the idle is now behaving as it should. Just for diligence, I also put 12V to the valve and it snapped crisply. I may still track down a spare for good measure.

Classic situation of putting in a new part (throttle body) only to have another one start to fail that's part of the same engine management system. Really tests the diagnostic skills!

Thanks everyone!
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'87 GL w/ Reimo top