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Discussion Starter · #21 · (Edited)
eBay & eBay in Europe is the best place for ISV. Shop for them by the Bosch part number not the VW part # and save a few $100


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What is the Bosch part number sir?

I copied this from your old thread from 2013:
  • HELLA: 6NW009141161
  • OEM: 408202011002 247319
  • STANDARD: AC406
  • VAG: 037906457C
  • VDO: 408202011002Z or 408 202 011 003Z
I am finding one on FCP Euro that is part number 037906457E. Most of these cars are 93 and up used on ABA cars. What is the difference between - functionally - this one and the C? They seem to both be dual pin, just a little difference in appearance. I figured best idea would be to get a fresh one from a place like FCP Euro if possible but am just curious if this one would actually work.
 

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For testing purposes you can simply unplug it. Every time the ignition is switched OFF the ISV’s jacking piston moves to the warm engine position. If you unplug it with the ignition OFF it’ll remain in that position indefinitely, eliminating fluctuations.

There’s a performance bypass and then a diagnostic one. I’m talking about the latter.

The ISV is wired to the ECU and if you unplug it while the car is running it’s possible you’ll fry the ECU. It’s not a big deal, though, just disconnect and reconnect with it OFF.

P.S. make sure the ignition is OFF
 

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Discussion Starter · #24 ·
For testing purposes you can simply unplug it. Every time the ignition is switched OFF the ISV’s jacking piston moves to the warm engine position. If you unplug it with the ignition OFF it’ll remain in that position indefinitely, eliminating fluctuations.

There’s a performance bypass and then a diagnostic one. I’m talking about the latter.

The ISV is wired to the ECU and if you unplug it while the car is running it’s possible you’ll fry the ECU. It’s not a big deal, though, just disconnect and reconnect with it OFF.

P.S. make sure the ignition is OFF
Hi sir, i disconnected it with the ignition off when i disconnected it. When i turned the car back on it was perfectly fine. Which is leading me to believe my ISV is dirty and sticking shut, or going bad. It resistance tested just fine so i started by cleaning it. Cleaning it actually helped a lot. It still did it a little on the first start the next day but not one time after that. I’m thinking this ISV may need a little more cleaning or may be going bad


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Hey Matt, what’s the consensus on cleaning ISV’s. There were posts in the past that carburetor cleaner would kill them. Any truth to this you’re aware of?


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Discussion Starter · #26 ·
Hey Matt, what’s the consensus on cleaning ISV’s. There were posts in the past that carburetor cleaner would kill them. Any truth to this you’re aware of?


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Im curious on the same thing. I cleaned mine with MAF cleaner because i read carb cleaner hurts them


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I’ve cleaned them and had success, but it’s usually short lived. The problem is rust. The ones I’ve cut open looked like they’d come from a Corrado sitting on the sea bottom, which one could argue is where they belong.
 

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Discussion Starter · #28 ·
I’ve cleaned them and had success, but it’s usually short lived. The problem is rust. The ones I’ve cut open looked like they’d come from a Corrado sitting on the sea bottom, which one could argue is where they belong.
So, in your opinion would it be better to just cut them out as a whole? Or just keep getting a new one off eBay - or wherever you can find one now - every time one dies on you?
 

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K, good info, ty. They’re plentiful and inexpensive because so many other vehicles still use them. So, get a new, aftermarket unit off eBay and enjoy for another decade. Resolved

I’ve cleaned them and had success, but it’s usually short lived. The problem is rust.

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A new one should last you a decade, at least. Part of the stigma surrounding ISV’s is that crappy used ones keep getting passed around. I get that they’re expensive and people seek used ones as relief, but it’s likely already rusted.

There’s no preventing the rust because it comes from the moisture in the air and it doesn’t help that the ISV itself isn’t sealed. I posted pictures of one years ago that I cut open to show the rust carnage.

The rust will compromise the connections behind the black connector first. That’ll result in voltage fluctuations to the electromagnet and make the idle hunt. Not a Corrado specific problem by any means, it affected all VW’s from that era. I diagnosed and replaced so many that I wanted to know what the hell was going on - rust.

- VW was well aware of the issue and took no action. Surprised?
 

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Discussion Starter · #32 ·
This one i got seemed to have only lasted a year. I bought this one about a year ago when the original one seemed to have crapped out. The cleaning i did seemed to have only lasted about a week or so because its back to doing the same thing. Im almost positive it is ISV because when i unplug it and start the car, it doesnt give me that issue. After i had cleaned it last time it also was fine. Maybe i just drew the short straw when i bought this ISV since it only seemed to have lasted me a year haha


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Discussion Starter · #33 ·
Cleaned the one that I have more thoroughly and it started up just fine with the valve plugged in. I am going to see if I can last a little bit on this one until I get a new one. I found one on eBay for $40 coming from China. Way better reviews than the one that is currently on the car. I will order this bad boy up soon.
 

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Discussion Starter · #34 ·
Hey all, here’s an update on the starting situation. I have a new ISV ordered - estimated delivery on November 5th I think - but here is the cold start of the day. This is the FIRST startup in a couple of days. The blips are not me touching anything. Also the AFR started at an 11.2 which to me seems way rich to start? Maybe turn the CO Pot up in ohm some more?


https://youtu.be/ExxSwmFInEU


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I was having an issue with my idle (VR6) 2 summers ago where the idle would go high and stay high after starting, but then settle down a while later. I assumed it was the throttle body, since I had a similar issue with a Scirocco I once owned, so gave it a good cleaning and lubrication, but it looked fine, and that didn't solve the issue. I ended up taking the ISV off and thoroughly cleaning it with brake parts cleaner and then something else I can't recall now, perhaps Triflow. So far that fixed the issue. Can't say that's what's going on with your car, but it's a relatively easy task to do so worth a try before spending money on new parts. 2 years later, still no reoccurrence. I checked the hoses for cracks and used new ear clamps just to make sure there were no leaks.
 

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Discussion Starter · #36 ·
I was having an issue with my idle (VR6) 2 summers ago where the idle would go high and stay high after starting, but then settle down a while later. I assumed it was the throttle body, since I had a similar issue with a Scirocco I once owned, so gave it a good cleaning and lubrication, but it looked fine, and that didn't solve the issue. I ended up taking the ISV off and thoroughly cleaning it with brake parts cleaner and then something else I can't recall now, perhaps Triflow. So far that fixed the issue. Can't say that's what's going on with your car, but it's a relatively easy task to do so worth a try before spending money on new parts. 2 years later, still no reoccurrence. I checked the hoses for cracks and used new ear clamps just to make sure there were no leaks.
The first time that I cleaned the ISV it helped a lot but I have cleaned it a second time since then, and it hasn't really done much to help anymore. I ordered a better quality one this time in hopes that helps haha
 
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