1200-1300 RPM idle warm

[Glassmuseum]

I’m having a high idle issue on my 86 turbo when it’s up to temp

I just replaced the ISV because I was having a wandering idle issue. I did a smoke test and the ISV was leaking like crazy so I assumed it was bad and needed to be replaced. the car is idling smoother now... However, once the car is warmed up it idles between 11 and 1300 RPM. The idle adjustment screw is completely tightened all the way. It does occasionally go down to 900 to 1000 RPM after it’s warm, but it always ends up back around 12 to 1300 and never settles. It seems to start doing this after driving.

Things I’ve done:
1. Performed a smoke test after installing the new ISV and it is still leaking. No other vac leaks that I can find. Can someone clarify if the ISV should be leaking? I would assume not.
2. Tested the TPS with carpokes instructions. No issues.
3. I adjusted the stop, the TPS so it clicks when the throttle barely opens, and I’ve defeated ISV and adjusted idle.
4. Replace the 3 pin EV1 ISV connector because it was pretty eaten up
5. I did replace the larger O-ring that connects to the intake from the throttlebody a few months ago.
6. New intake gaskets
5. The car has a pretty new dme temp sensor as well.

The only clue I have right now are: if I squeeze the TPS against the throttlebody, the idle goes down to a more reasonable level. Probably about where it should be. I’m wondering if the throttlebody seals have just given out but also wondering why it would have passed the smoke test. Wouldn’t I have seen smoke coming out of the side of the throttlebody? Any other tips on how to confirm this?

The other thing I’ve noticed is when I start the car cold for the first time, it seems to idle just fine. This seems the only start coming up after I drive the car or rev it.

Could it be time to rebuild the throttlebody? Or do I still maybe still have another faulty ISV? Even though it’s brand new I didn’t see any other vacuum leaks after the smoke test so I’m a puzzled. But since I press on the ISP and I noticed a But since I press on the TPS and I noticed a difference, and it seems to happen when the throttle is pressed and the car is driven, it leads me to believe that there’s something kind of screwy happening in the throttlebody or throttle cable. Any thoughts?

[spacecad3t]

I went through much of the same experience with my NA, alot of conversation was captured here: https://www.carpokes.com/viewtopic.php?t=4557

In the end mine was a combo of Throttle Body, TPS, and ICV. My throttle body would not show much smoke during a smoke test, but installing a rebuilt TB made a difference. I also discovered in the process that my TPS didn't have an o-ring. Then, I found that my ICV was just not closing correctly. Now my car idles correctly and I can open the throttle bypass and adjust the idle.

[soxnail]

If you take a look at this thread especially the last page,
https://forums.pelicanparts.com/porsche ... valve.html
My apologies it is on another board...You should find the relationship between a ICV that was leaking past the valve and idle rpm. It was brand new. Still I could not get the idle down no mater what.
Sox

[Bergerac]

Are you doing the smoke test when its hot? Sounds like you have a vac leak that only occurs when something gets hot and expands.

[Tom]

Probably a combination of leaks. The ISV should not leak, but if pressing the TPS against the throttle body lowers the rpms, it's probably leaking unless you are also pushing the plate further closed... Smoke tests don't always show small leaks, especially low pressure smoke tests. Spray starter fluid on the suspects and see if the rpms change -- if so, it's getting sucked in through the leak.

[Glassmuseum]

I went through much of the same experience with my NA, alot of conversation was captured here: https://www.carpokes.com/viewtopic.php?t=4557

In the end mine was a combo of Throttle Body, TPS, and ICV. My throttle body would not show much smoke during a smoke test, but installing a rebuilt TB made a difference. I also discovered in the process that my TPS didn't have an o-ring. Then, I found that my ICV was just not closing correctly. Now my car idles correctly and I can open the throttle bypass and adjust the idle.

If you take a look at this thread especially the last page,
https://forums.pelicanparts.com/porsche ... valve.html
My apologies it is on another board...You should find the relationship between a ICV that was leaking past the valve and idle rpm. It was brand new. Still I could not get the idle down no mater what.
Sox

Wow these are both epic threads, thank you for posting them. going to read through them!

[Glassmuseum]

Are you doing the smoke test when its hot? Sounds like you have a vac leak that only occurs when something gets hot and expands.

Very good point. I am going to try this tomorrow.

Probably a combination of leaks. The ISV should not leak, but if pressing the TPS against the throttle body lowers the rpms, it's probably leaking unless you are also pushing the plate further closed... Smoke tests don't always show small leaks, especially low pressure smoke tests. Spray starter fluid on the suspects and see if the rpms change -- if so, it's getting sucked in through the leak.

Very weird that a new ISV was pouring smoke out of it. The old one and the new one. Same spot where those tabs are at the bottom. I got the new one from 944 online and seems like a good unit. But who knows..

Here is a video showing how squeezing the TPS changes the rpm’s. I think since the TPS checked out when I bench tested it, I am probably looking at a TB rebuild. I’ll try the starter fluid method as well