Carpokes

My oh my! This is why I am reluctant to buy a second 944 unless it is totally vetted mechanically. I live in Central ORegon and the last 944 shop packed it in several years ago. There are several Porsche shops and of course the dealer but they hate our beloved transaxle cars.

07turbeaux wrote: Mon Dec 01, 2025 10:46 pm My oh my! This is why I am reluctant to buy a second 944 unless it is totally vetted mechanically. I live in Central ORegon and the last 944 shop packed it in several years ago. There are several Porsche shops and of course the dealer but they hate our beloved transaxle cars.

My cars are all project cars, I knew this going into it. However, I do not have a garage, I have some family with a garage/lift I can access but they are 8 hours away. So I research mechanics in my region (NE) for when I just cant do it myself. Or plan my big projects and include a road trip... I deleted my power steering this year, installed a manual rack kit. I drove the car for months leaking fluid, drove it the 8 hours leaking fluid. Did the work on my dads lift. Drove it 1600 more miles and returned home.

Well, it was nice out today and I decided to smoke the engine again... I think I found my leak leading to my 1100 idle. No where else is showing smoke.

spacecad3t wrote: Wed Mar 18, 2026 1:04 pm Well, it was nice out today and I decided to smoke the engine again... I think I found my leak leading to my 1100 idle. No where else is showing smoke.

Always hard to know how bad a leak is with a smoke test, but that's not screaming huge leak to me -- i.e., not a leak big enough to cause an 1100 rpm idle despite the ISV/DME doing everything it can to bring it down. If you can't find any other vacuum leaks (my first guess), then what happens when you physically block off the ISV hose? If the idle then drops to normal or below, look closely at the ISV and ISV controls. If the idle remains high with the ISV hose blocked off, then what ever happened with the throttle plate gap issue you had asked about? Air has to be getting in "somewhere" for an 1100 rpm idle -- the only question is where... Of course, first be sure to set the base idle (if you can) making sure the throttle stop, throttle cable, and cruise control cable (if present) are not holding the throttle plate open. And, if you've only looked for vacuum leaks a dozen times, I'd go back for a thirteenth look. Leaks can be tricky to find...

Damnit

Tom wrote: Wed Mar 18, 2026 1:30 pm

spacecad3t wrote: Wed Mar 18, 2026 1:04 pm Well, it was nice out today and I decided to smoke the engine again... I think I found my leak leading to my 1100 idle. No where else is showing smoke.

Always hard to know how bad a leak is with a smoke test, but that's not screaming huge leak to me -- i.e., not a leak big enough to cause an 1100 rpm idle despite the ISV/DME doing everything it can to bring it down. If you can't find any other vacuum leaks (my first guess), then what happens when you physically block off the ISV hose? If the idle then drops to normal or below, look closely at the ISV and ISV controls. If the idle remains high with the ISV hose blocked off, then what ever happened with the throttle plate gap issue you had asked about? Air has to be getting in "somewhere" for an 1100 rpm idle -- the only question is where... Of course, first be sure to set the base idle (if you can) making sure the throttle stop, throttle cable, and cruise control cable (if present) are not holding the throttle plate open. And, if you've only looked for vacuum leaks a dozen times, I'd go back for a thirteenth look. Leaks can be tricky to find...

"...then what happens when you physically block off the ISV hose?"
It does come down in RPM... I think the ICV is working as intended.

"...then what ever happened with the throttle plate gap issue you had asked about?"
That was my old throttle body. This throttle body checked out better, very little gap.

"...making sure the throttle stop, throttle cable, and cruise control cable (if present) are not holding the throttle plate open."
No cruise, but stop and cable, 4x checked. Plenty of slack and the plate is goning to smack the bore if I take the stop down any more, besides... with a running engine it doesn't change the rpm is I back the stop off.

They are tricky... I purchased a hand pump pressure tester... maybe that will help revel something.

Also @Tom, I just went back out to test the battery voltage at start and running, and the damn thing idled perfectly the entire time... Here is a video I started taking after it wasn't acting weird... just note, my tach is confirmed 150rpm off, so this would roughly be 850rpm.

At 0:35 it would actually be LOW, like 800 or 750 and the car does stumble, when I give it gas it evens out and it appears to me the ICV is pushing it back up to the target idle.



A couple of questions.

Should my fog lights cause my voltage to dip that much? I'm seeing 14v with no consumers on, 13.5 with headlights on, then down to 12.5 or less with the fog lights on.

I have cleaned all of the grounds and replaced the battery grounds- could I have a short somewhere causing a weird voltage issue translating into weird idle control at random times?

"Should my fog lights cause my voltage to dip that much? I'm seeing 14v with no consumers on, 13.5 with headlights on, then down to 12.5 or less with the fog lights on."

Are you at idle doing this? Does the voltage come back up with some throttle applied? These cars don't have the strongest alternators known to man.

""...then what happens when you physically block off the ISV hose?"
It does come down in RPM... I think the ICV is working as intended."

I wonder if the butterfly close wire to the ICV is intermittent.

@944er "...Are you at idle doing this? Does the voltage come back up with some throttle applied? These cars don't have the strongest alternators known to man."

It does, I was just surprised to see it drop so much for the fog lights, compared to the headlights...

"...I wonder if the butterfly close wire to the ICV is intermittent."

I have tried massaging the wire loom and other tests... but I also wonder if I should just get another ICV and find out... I do notice that it will sometimes idle fine, I drive a little bit, come off the throttle and return to idle, where it's now idling around 1050-1100, but I haven't been able to blip the throttle or anything to reset it. Sometimes I shut the car off to go into a store or something, and when I turn it back on, the idle is reset to normal.

I wondered if this was also a sticky TPS, but same behavior with 2 throttle bodies and 3 switches.

Im also wondering if an old reference sensor could cause incorrect RPM readings? I have no trouble starting the car, or with it remaining running and RPM's appear consistent across the range, confirmed with a timing gun. The only thing I confirmed was that my tach is off by ~150rpm.

My two cents... I agree with the alternator comment and would want to have the alternator load tested. Some voltage drop is normal when you turn on all the lights, but in that video it just keeps dropping and went as low as 12.2v -- something's not right there. If you have cleaned the terminals and all the grounds, and the battery is healthy, then the alternator is the prime suspect.

On the intermittent high idle, my hunch would be a harness issue -- specifically the wires under the rubber boot on the ISV. That connector is a classic Junior timer just like the speed and ref sensors, injectors, etc., and they all eventually suffer from frayed and cracked wires under the boot. See more than you ever wanted to know about them here:

https://www.carpokes.com/viewtopic.php?t=565

Also, have you reset the base idle? If it is close to the limit of the ISV's ability to control, there may be circumstances where the ISV is able to bring the idle down to spec, and circumstances where it is not. The fact that the idle goes down when you block if off suggests the ISV is not closing as much as it could/should when the idle is high.... My first guess is the connector though...

And I didn't mean to completely discount the throttle body. I doubt it's the cause of the high idle, but I'd still want to reseal it. 944online carries our reseal kits, and the instructions are posted here on Carpokes if you want to get a sense for what's involved.

https://www.carpokes.com/viewtopic.php?t=4972