Carpokes Porsche Forum

Tom wrote: Wed Nov 05, 2025 7:16 pm Can you log engine parameters with th le F9 DME?

I dont think so, I didnt get the ODB DME, it was out of stock at the time.

Have you tested the TPS signal at the DME connector, to make sure the idle switch signal is making it to the DME? I'd also cap off the ISV ports to see if that's were the air is getting in...

Tom wrote: Wed Nov 05, 2025 7:37 pm Have you tested the TPS signal at the DME connector, to make sure the idle switch signal is making it to the DME? I'd also cap off the ISV ports to see if that's were the air is getting in...

I have tested the TPS, the thing that keeps me up at night is if the TPS tests fine at the DME while sitting parked, but gets stuck while driving...

The ISV and hoses are all new, didn't see any smoke from them. You think it could be leaking just enough?

spacecad3t wrote: Wed Nov 05, 2025 8:16 pm

Tom wrote: Wed Nov 05, 2025 7:37 pm Have you tested the TPS signal at the DME connector, to make sure the idle switch signal is making it to the DME? I'd also cap off the ISV ports to see if that's were the air is getting in...

I have tested the TPS, the thing that keeps me up at night is if the TPS tests fine at the DME while sitting parked, but gets stuck while driving...

The ISV and hoses are all new, didn't see any smoke from them. You think it could be leaking just enough?

Once it is warmed up and running fast you can pull the TPS connector and short out the idle contacts to rule it out. For the ISV, blocking the ports will just eliminate (or reveal) a source of extra air...

Tom wrote: Wed Nov 05, 2025 8:30 pm

spacecad3t wrote: Wed Nov 05, 2025 8:16 pm

Tom wrote: Wed Nov 05, 2025 7:37 pm Have you tested the TPS signal at the DME connector, to make sure the idle switch signal is making it to the DME? I'd also cap off the ISV ports to see if that's were the air is getting in...

I have tested the TPS, the thing that keeps me up at night is if the TPS tests fine at the DME while sitting parked, but gets stuck while driving...

The ISV and hoses are all new, didn't see any smoke from them. You think it could be leaking just enough?

Once it is warmed up and running fast you can pull the TPS connector and short out the idle contacts to rule it out. For the ISV, blocking the ports will just eliminate (or reveal) a source of extra air...

I have tried shorting the TPS at temp, I didnt observe a change, but for all I can tell, my TPS is doing its job, in a NA at least which is binary switching between idle and WOT. I think only the turbo has "off idle" and "partial throttle" relative to knock detection I assume.

I can blip the throttle, or more importantly enter decel from higher RPM and I can hear/feel the engine switch to decel/fuel cut off. Wouldnt a non-working TPS, say one that is stuck open, not trigger decel and stay in WOT the whole time?

I had not thought of blocking the ICV, is there a simple way you do this? Pinch the ICV intake hose? I have some fuel line clamps that might work.

Short list of things to try:
- Unplug O2 while idling high at temp.
- Plug/block ICV hose while idling high at temp.
- Continue to check engine harness...

Here is the testing procedure for the TPS, if not seen already:
https://clarks-garage.com/shop-manual/fuel-06.htm

The NA 8V (and 16V) actually has three fuel maps in the DME: idle, part throttle and WOT. So when testing the TPS we test for idle connection and WOT, knowing that when the DME doesnt read either of those states, its using the part throttle maps. So its important that the TPS is working correctly to identify idle and WOT or the DME will be defaulting to the part throttle map.

walfreyydo wrote: Thu Nov 06, 2025 5:38 am Here is the testing procedure for the TPS, if not seen already:
https://clarks-garage.com/shop-manual/fuel-06.htm

The NA 8V (and 16V) actually has three fuel maps in the DME: idle, part throttle and WOT. So when testing the TPS we test for idle connection and WOT, knowing that when the DME doesnt read either of those states, its using the part throttle maps. So its important that the TPS is working correctly to identify idle and WOT or the DME will be defaulting to the part throttle map.

I think you are correct. I retested the TPS at the throttle body following Clarks. I made some videos:

Pin 2, Idle "With the throttle closed, the ohmmeter should read zero (0) ohms. With the throttle open, the ohmmeter should read infinite (∞)."
https://vimeo.com/manage/videos/1134255056

Pin 3, Open "With the throttle closed, the ohmmeter should read infinite (∞). With the throttle wide open the ohmmeter should read zero (0) ohms."
https://vimeo.com/manage/videos/1134255113

So from what I see, Pin 2 is stuck saying "open throttle", even when closed, and even with an audible click.
And, Pin 3 is working as intended. So... the car starts and warms up and idles fine. First blip of throttle puts into a stuck "open throttle at idle" situation?

For what it's worth now, here is a video of it running warmed up and idling at ~1100, given the vac gauge reading, it does appear to be "off idle" to me. I show how my cable has slack and the throttle plate does not need to close further.
https://vimeo.com/manage/videos/1134243746

Or I don't know because I just performed the same test on another throttle body and TPS and got the same outcome.

Edit/update: I have a throttle body and several salvaged position switches. Swapping them out and testing them, all the same. Pin 3 seems to test as the procedure says, Pin 2, infinite only. I can hear all the switches double click... I must have something wrong.

Update/update: Am I crazy, watching my videos again the resistance measurements seem flipped, no? Testing terminal 3, I see 0ohms closed and infinity when open..,

I have my pins backwards like a goon

I think I solved it...

So measuring resistance correctly... My WOT was correct, but my idle was not going to infinity consistently.

I stepped back and loosened everything... I mean the cable and the stop set screw. Assuming it was untouched, that turned out to be it. I was able to back it off and readjust it. TPS now switches idle correctly and car is idling as it should be.

Thank you all.

Glad to hear to got this resolved! I had the same issue when first going over mine. If the idle was set where it wouldn't make the switch at idle, it would idle a little high. Which wasn't so bad. The problem was that it stumbled when coming off idle and also dropped RPM low with a quick let off the throttle. Adjusted idle speed and the TPS. All good.