FredR

I think the best thing you can do with the ISV is remove it from the car and inspect the shuttle valve. This should move smoothly side to side with light pressure from a finger. If it does this and the ISV does not work then the chances are it is shot assuming the connector was making contact. The ISV can be tested but you need something along the lines of an oscilloscope/signal generator to derive the appropriate actuation signal.

I had a problem with my ISV many years ago & was told I needed a new ISV. I just took the bull by the horns and removed the inlet manifold [for the first time] and pulled the ISV. What I found in the ISV was what looked like a black powdery substance- I expected to see something oily but surprisingly it was dryish and the shuttle was "sticky". I used a cotton rag on the end of a wooden spoon to clean the deposition up and that seemed to free up the shuttle. I dare say you could use a carb cleaner spray to clean it up at this stage although I tend to be a bit careful about where I use that stuff. Once the shuttle was moving freely I did not see any point in trying anything else- boxed it all up and it worked nicely.

If and when I remove the inlet manifold I usually pull the ISV, take a look in the port and if the shuttle is clean and it moves freely I just put it back again. 14 or whatever years on the same item still works nicely.

I am completely with Sean on not squirting stuff into the inlet tract- there is a very sensitive/expensive piece of kit in there that may not react too nicely to a backfire. I can get the manifold off and back on again in a good afternoon's work providing nothing much else needs doing or goes wrong. The worst bit is dealing with the ISV connector I do not have the tool] - nowadays I install it with the spring clip removed to make removal easy- why Porsche did not supply an external connector is beyond me. If the connector loses contact you just push it back and that has only happened once and most likely becuase I did not push it back on fully. I have a couple of connectors I purchased from Roger to make an extension of the wiring such that I can break the connection external to the manifold- I might even make it and fit one of these days when I next remove the manifold!

Rgds

Fred

worf928

ISV can be tested in the car without a Bosch Hammer. Instructions are in my inspection guide.

928mac

Thank you all.
I have an electromotive system. I can see and demand on/off or set my perfered idle rpm from my laptop.
The car idles when warm but not so well when first starting cold as its low.
The system is asking for higher idle but its not happening. Its never worked in my opinion, its just my fuel enrichment that I have setup according to engine temp that keeps it running.
So, as per my original post I was just wondering if it can be tested off the car and how it could be done to verify that it works correctly.

From what I gather from the post above, The Idle valve operates on a square signal and not variable voltage and I don't have an oscilloscope so I guess I'm hooped.

Thank you all for your help.

Brad

worf928

Are you asking how to test your ISV or how to see the signal going to the ISV? The first question has been answered: you can test it in the car or on a bench without a Bosch Hammer. If you want to see what's going to it then you need a 'scope. If you want to generate a square wave you'll need a signal generator.