Big loss of power w/ A/C on

[Howesight]

Audi and VW both used the pulse-width-modulated idle stabilizer valve (ISV)for years. Both exhibited the same behaviour when they were old. Remember that the ISV operates by rapidly moving a piston back and forth, varying the amount of time it is held "forth".

They wear and also get gummed up and when that happens, they get sticky. The intermittent high idle is a classic symptom of a stuck or sticky ISV. Engine compartment heat can make the ISV stick since some parts are steel and some are aluminum. ISV's can be cleaned and lubricated, but that is really just a Hail Mary fix to allow you to finish a long trip. Substitute it for new or known good ISV and you may find a dramatic improvement.

As for GoWesty's EFI, I am not sold, but then again, I am a born do it yourselfer. The main items that trouble the Digifant system due to wear are the throttle body, the cam that operates the TPS, and the AFM, in that order of priority. You have to do some pretty crazy shit to ruin a factory VW fuel injector. They clean up nicely with any commercial injector cleaning system. There are a number of throttle body rebuilders now. Ditto for the AFM. (Or, you can buy mine, new with only 5,000 miles.)

I have done standalone EFI on several vehicles, so I am not impressed with the price of the GoWesty system considering how little benefit it will deliver. Replacing the above-mentioned items, if testing proves replacement is needed, will give excellent results. The one thing that every Vanagon over 100,000 miles absolutely needs is a rebuilt or aftermarket throttle body since they do wear out causing poor idle, emissions failures, etc.

The only thing about the GW system that actually improves on the Digifant system is knock control. You can add a very high quality knock control system for only $595.

Here is a link to the J&S Electronics website:

http://www.jandssafeguard.com/index.html

With knock control, you can run maximum spark advance to achieve maximum MBT and high compression without fear of destructive knock. These are two things that can give a decent power increase.
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'86 Syncro Westy SVX

[RBEmerson]

Wowsers! I'm beginning to feel enlightened.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[ohhorob]

[RBEmerson]

I think at this point the issue of the throttle body is resolved. I have no confirmation that the existing one is the original, but I suspect it is. At least I can find no record of the EFI being repaired or updated in connection with putting the 2.2L engine in, and before that, definitely no record of changes. So, call it a throttle body with 200K on it. Ditto for the ICV. Changing the throttle body fixes the TPS-related issues - that's a two-fer. And I get the idea of engine bay heat raising havoc with a varnish-gummed ICV that's hummed away for 200K.

Right now all I know about for sourcing these pieces is GW has throttle bodies, Van Cafe has Jetta ICV's. If I can trim some money off the project, that's a good thing. Alternate vendors for these items?
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[RBEmerson]

Basta! I ordered a throttle body from GW, and the ICV from Van Cafe (no TB's from VC, no ICV from GW). It's spendy(!!) but I have no faith in the original parts. All that's left is to replace them.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[Gizmoman]

[RBEmerson]

"Hope springs eternal..." and all that. When I look at all of the Westy's records, it's a puzzle that the PO and I don't hold a controlling interest in GW. [/LOL]
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[Terry Kay]

I don't hink the premature odering of any parts was necessary--yet.

It's yet to be determined.

Is there a big wobble in the throttle shaft?
The plate or the bore is wore off or hogged out so bad it isn't sealing?

I wpuld have held on for a few more days till you get the TPS ironed out first--prior to ordering anything.
You already mentioned that the switch is clicking--that is the first good sign.
It just may be outa wack a hair, and causing the problems.

Been there, seen it--and done it many times to iron out an off idle or high idle issue.
Poor fuel economy is another problem associtated with the switch being outa wack--
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T.K.

[RBEmerson]

I'm running out of time. It's drastic overkill to replace the parts first and ask questions later, but I gotta cut to the chase.

FWIW, the aCar app (tracks mileage, costs, etc.) reports a 3-month average of 19.2 MPG. I think that's on par with most Vanagon mileage reports.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[RBEmerson]

An update to close this thread. I replaced the throttle body (lots of wear in the throat, the shaft slides up and down as it's rotated) and ICV (new ICV buzzes loudly). So far, so good. I'm still seeing the racing engine while standing with A/C on. I'll start a new thread to deal with a couple of questions on this issue.
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.

[hecbom]

RB I have same issues as you described. I also have a 2.2L with the original FI but three years ago, I replaced the ICV with a new one. I also replaced the TB with a rebuilt one from Van Café. It still idles high around 1800 to 2000 rpm when the air comes on. Last I also rebuilt my A/C just like you did, with a new compressor, hoses, EV and dryer. I would be interested in knowing what you find out, likewise if I hit on a fix, I will post.
Thanks
Hector

[Howesight]

Hey RB:

You might now find that the IS control unit is the culprit for your remaining symptom of high idle while AC is on. Here's what I have gleaned from Bentley, Pro-Training and a bit of experience and intuition:

1. The ISCU has a base idle speed for no-load when the engine is warm.

2. It also has a set of programmed values/outputs for different engine coolant temperatures while the engine warms up.

3. For power steering switch input, it senses either "on" or "off" from the pressure sensor and raises the duty cycle of the ISV a given amount. You can check this by short-circuiting the PS pressure switch wiring.

4. What I do not know, (but I have my theories), is what happens when the "AC on" signal from the AC compressor clutch goes to the ISCU. Did VW program this signal to output the exact same duty-cycle change as for the other "on/off" input - - the PS pressure input - - or did they set up a separate algorithm for the AC input?

5. Both the PS idle-up and the AC idle-up features are, so far as I can tell, triggered by simple "on/off" inputs. This means that faulty wiring (eg corroded with added resistance, bad grounds) will not likely be the culprit.

6. This is why, by process of elimination, I reckon you might have an ISCU that is dying.

The trouble-shooting tests for the whole idle stabilization system are in the Vanagon Digifant Pro-Training manual. Here's a link to a PDF of the manual:

http://www.vanagonauts.com/files/Vanagon%20Digifant%20Fuel%20Injection%20System.pdf

Here's what Van Café says about the ISCU:

"Idle Stabilizer Control Unit (rebuilt) ICU
251.907.393DX

This part is mounted in the cavity behind the passenger side tail light housing (you remove the tail light for access)- When mounted correctly, these are supposed to plug in downward, but occasionally people remount them so that the control unit faces upward- If you find yours mounted with unit facing upward, correct it as moisture tends to collect in them when installed incorrectly. New ones disappeared a few years ago. We are pleased to be offering these rebuilt units. These rebuilt units have been inspected to determine if they are a suitable candidate for rebuild, disassembled, repaired, "hardened", assembled, and re-tested. The folks rebuilding these use new components as needed - and they have added a silicone coating to the rebuilding process to reduce the likelihood of future water damage."

They wouldn't be selling any (nor insisting on cores) if the ISCU units weren't failing. Classic case, I suspect, of capacitor failures, but that's just my speculation.

If you don't like spending $189 at Van Café, grab a low-tech electro-mechanical Dijijet idle-up switch from a pick-n-pull and install. Or get an adjustable Toyota pick-up/4runner (1985 to 1997) unit and install. Disconnect the compressor clutch wiring from the ISCU if you do this. If you find your AC performance at idle is poor, then raising the idle speed (although not to the 2,500 rpm you now have) can be helpful.
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'86 Syncro Westy SVX

[jberger]

Throwing parts at something is not the answer. Especially when those parts are controlled or adjusted by other components.

1, Throttle body\switch adjustment is .002-.004" from closed. IIRC the stop screw adjustment is purely to make sure the EVAP purge valve vacuum circuit is closed off at idle. That can be verified by a vac guage attached to the throttle body nipple.

2, The aux air control valve must be set at its mid span per the pro training manual by using a Milli Amp meter. VW has a special tool for it, but you can run a milli amp meter in series with the harness connector and valve. The Amps are adjusted by turning the idle bypass screw in or out to attain the proper range.

If these items are not set correctly you will not achieve proper throttle response or idle speed control.

[Howesight]

[jberger]

My terminology was incorrect. I am talking about the buzzing valve in the digifant system. The iav or whatever the proper name is, is essentially an aux air valve. It allows metered air to bypass the throttle body. Acting exactly the same as if you were resting your foot on the throttle.

[RBEmerson]

This is, in great measure, a "throw enough spaghetti on the wall until something sticks" approach to the issue. However, I'm using Bentley, the Digifant manual, as well as insights here, to select what seems the spaghetti most likely to stick.

As I wrote earlier, I'm hard up against a time crunch; it's faster to replace the obvious culprits than to spend tons of time, something I just don't have, troubleshooting.

There's no doubt the throttle body was in trouble. The throttle plate was worn, there's a groove in the throat left by the plate as the shaft moved up and down. The idle control valve, at the very least, didn't buzz loudly, if at all (my hearing isn't that great). The new valve's buzz or hum is hard to miss. In short: they were broke, I fixed them.

The Temp II sensor is another strong contender for causing the racing engine problem, so that will be replaced outright.

The air flow meter looks pretty good on the ohmmeter, so I think that can be left alone. "All" thats left is to re-check for vacuum leaks, poor connections (although any connector I've played with recently has been doused with contact cleaner), and check the oil breather.

On the TPS, TerryK sent a video on a detailed setup. The new GW TPS will not set up as per Bentley. That is, no way can I get down to the .003" gap called for. Frankly, I'm surprised at how lame this assembly is. NTL, I dialed it in as close to spec as possible. The overall drivability is much better than their setup. Their setup has a gap of 4-5/32"!!!
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Lord, give me coffee to change the things I can change, and wine to accept the things I can't change.