Carpokes Porsche Forum

Hi y'all

I recently picked up a smoke tester to help in diagnosing a friend's 190e 2.3-16 that most certainly has vacuum leaks. I figured I may as well try it on my 951 to see if there are any hidden boost leaks that I wasn't aware of. Sure enough, I have at least 2 vacuum/boost leaks!

I need some input on figuring out if the leak I have on the idle control valve is supposed to be there. With the car off, I am getting smoke coming out of what I suspect are the ports for the controlled vacuum leak when the ICV is open. See the port (?) circled in red below. I am guessing the ICV circuit opens to let in additional air when the car is cold, and shuts once the car is warmed up. Is the ICV supposed to be in the closed position or open position with the car off?

A little backstory, I had my local Porsche shop install the venturi delete kit from Lindsey about a year and a half ago. Before I brought the car in, it idled when warm at around 850 rpm (if memory serves me right). After they did the work, it's been idling around 1050-1100. I tried doing the idle adjustment procedure listed below, but wasn't able to get the idle to change. https://www.clarks-garage.com/shop-manual/fuel-08.htm Assuming that the ICV is supposed to stay in the closed position when the ignition is off, based on my findings today and my inability to adjust the idle with the process in the link, I am guessing my ICV is bad? Are there any other systems that would cause the ICV to be open or have this vacuum leak when the car is off?

Re-seal your stabilizer.

Here is the McMaster link for the 3mm x 33mm ID

https://www.mcmaster.com/#5233T201

I believe the ICV never fully closes when the car is running. It is constantly compensating between fully open and closed.

Here are pics of mine I took apart a few years ago.

I measured the O-ring and I get 38mm outside diameter x 3mm thick approx.
The seat where the O-ring sits is 33mm.

I cleaned it with isopropyl alcohol. The alcohol worked very well and it is safe for use on the electrical parts.
If you look at photos 1 and 2 you see a round thing in the bottom where the long center pin/shaft sits into.

That piece floats loose in the bottom and sits under the six brushes you see. The brushes are very delicate and easy to bend or damage.

They can be straightened, if bent, using very long skinny needle nose pliers. I bent one with my finger by accident trying to straighten out the round cup part.

The cup part will rattle around in there like a dice in a cup. You just have to shake the housing to get it back to center where it is supposed to sit and the shaft will go back together properly.

Be very careful when pushing the winding back into the upper unit because it only goes in one way. If you are off by 90 deg the unit will not sit all the way up inside the upper portion "the section with the hose barbs" That part as seen in the photos secured in place by the clip.

There are two synthetic washers. One site at the top of the shaft. The other synthetic washer sits underneath the metal washer and then secured in place by the clip. You can see the groove where the clip goes.

Be sure to make note of the orientation of the unit when you take it apart. The center winding/upper hose barb section can go into the bottom section 180 degrees apart so make sure you get the correct orientation for that also.

I created a post April 3, 2017 on RL. This pretty much sums up my posts.

https://rennlist.com/forums/944-turbo-a ... lizer.html

I hope RL doesn't ban me for reposting my stuff

Great post! It's probably clear to @TurboD based on that write-up, but to drive it home, the area you circled is just a crimp point -- no air is designed to get in or out there. Most ISV's leak a little at this point. I wouldn't necessarily conclude a little leak there is the cause of a 1100rpm idle, especially if that started immediately after a shop did a venturi delete. I'd probably check their work pretty closely and see if the idle stays high even if you block off the ISV hoses.

If helpful, here's a video I did a long time ago showing a simple test for the ISV. With PWM, I'm sure you could come up with a more nuanced test to confirm it is opening and closing as much as commanded, but this all or nothing test at least tells you if it's alive or dead.




p.s., No joke, RL banned someone after trying to post a helpful link to Carpokes.

If my limited searching is correct RL is owned by a Canadian company in Toronto. If true I would consider stopping by their location with a CIWS mounted on a truck bed

Tom wrote: Thu Jan 23, 2025 10:49 am Great post! It's probably clear to @TurboD based on that write-up, but to drive it home, the area you circled is just a crimp point -- no air is designed to get in or out there. Most ISV's leak a little at this point. I wouldn't necessarily conclude a little leak there is the cause of a 1100rpm idle, especially if that started immediately after a shop did a venturi delete. I'd probably check their work pretty closely and see if the idle stays high even if you block off the ISV hoses.

If helpful, here's a video I did a long time ago showing a simple test for the ISV. With PWM, I'm sure you could come up with a more nuanced test to confirm it is opening and closing as much as commanded, but this all or nothing test at least tells you if it's alive or dead.




p.s., No joke, RL banned someone after trying to post a helpful link to Carpokes.

gruhsy wrote: Thu Jan 23, 2025 11:02 am If my limited searching is correct RL is owned by a Canadian company in Toronto. If true I would consider stopping by their location with a CIWS mounted on a truck bed

Tom wrote: Thu Jan 23, 2025 10:49 am Great post! It's probably clear to @TurboD based on that write-up, but to drive it home, the area you circled is just a crimp point -- no air is designed to get in or out there. Most ISV's leak a little at this point. I wouldn't necessarily conclude a little leak there is the cause of a 1100rpm idle, especially if that started immediately after a shop did a venturi delete. I'd probably check their work pretty closely and see if the idle stays high even if you block off the ISV hoses.

If helpful, here's a video I did a long time ago showing a simple test for the ISV. With PWM, I'm sure you could come up with a more nuanced test to confirm it is opening and closing as much as commanded, but this all or nothing test at least tells you if it's alive or dead.




p.s., No joke, RL banned someone after trying to post a helpful link to Carpokes.

Rennlist is now owned by Internet Brands in Los Angeles, which in turn is own by KKR, the huge private equity firm. Suffice to say the auto forums are not their highest priority. You are thinking of Vertical Scopes in Toronto, which owns big forums like BenzWorld and Planet 9, among many others. Vertical Scopes' main business is forums, and it shows.

Thanks for the very detailed write-up. Definitely sounds like I need to reseal or replace my ISV.

I tried to block off the feed back into the intake manifold from the ISV to see if that would drop the idle down, but was not able to get the car to run with said feed blocked off.

I suspect the high idle could be from this leak on the ISV and the leak I have on the throttle plate shaft. Thanks for the info and help!

TurboD wrote: Mon Jan 27, 2025 9:43 am Thanks for the very detailed write-up. Definitely sounds like I need to reseal or replace my ISV.

I tried to block off the feed back into the intake manifold from the ISV to see if that would drop the idle down, but was not able to get the car to run with said feed blocked off.

I suspect the high idle could be from this leak on the ISV and the leak I have on the throttle plate shaft. Thanks for the info and help!

Sounds like you need to start by resetting your base idle. There is a procedure for doing that where you deactivate the ISV via the diagnostic port and then set the idle with the screw on top of the TB. If the car won't run without the ISV blocked off, the base idle is probably way off. If you need details on setting the base idle, let us know and we can post the details.

Tom wrote: Mon Jan 27, 2025 10:43 am

TurboD wrote: Mon Jan 27, 2025 9:43 am Thanks for the very detailed write-up. Definitely sounds like I need to reseal or replace my ISV.

I tried to block off the feed back into the intake manifold from the ISV to see if that would drop the idle down, but was not able to get the car to run with said feed blocked off.

I suspect the high idle could be from this leak on the ISV and the leak I have on the throttle plate shaft. Thanks for the info and help!

Sounds like you need to start by resetting your base idle. There is a procedure for doing that where you deactivate the ISV via the diagnostic port and then set the idle with the screw on top of the TB. If the car won't run without the ISV blocked off, the base idle is probably way off. If you need details on setting the base idle, let us know and we can post the details.

Thanks Tom — if the idle adjustment procedure is the one in the link below, I did this a while ago when the issue first came up and was not able to get the idle lower than where it is now. If my memory is right, I needed to bring the idle screw down to the lowest setting just to get it to this 1,050-1,100 idle speed. If it's possible the car will not run with the idle screw at the lowest setting, my best guess is that's what would stop it from running with the ISV blocked off.

https://www.clarks-garage.com/shop-manual/fuel-08.htm

Yes, that's the test. Your tests all point to a leak somewhere. If the motor doesn't run at all with the ISV hose blocked off, then it stands to reason that's the source of the leak. But I'm still skeptical about that since it all started after the venturi delete. As a shade tree test, you could wrap packing tape around the ISV to seal it temporarily and see if that changes anything -- I'm kind of doubting it will, but easier and quicker than trying to pull the ISV apart to change the o-ring.

Haven't heard the term "shade tree mechanic" in a while! Thanks for the chuckle...

I'll seal the ISV with some tape when I have the chance to and report back. I did get a video of the smoke billowing out of the ISV and coming out of the throttle body shaft, but wasn't able to upload do to file size. But, judging by the amount of smoke during the smoke test and the strong hiss from the ISV when running, it's my strong suspicion!