Kroon Harness for 944 Turbo

[Latitude48]

...
If my line of thinking is somewhat correct, the issue would have to be one or some of the following:

1) Vacuum system component that has remained untouched before or after the engine replacement
2) I forgot to tighten a clamp somewhere, each and every time I have worked on the car
3) Timing actually being off, despite what the timing marks being correct
4) Something in the valvetrain being off or not working?
-Head was rebuilt about 2 years ago, but I'm still using original lifters (170K miles and 40 years old)
5) I'm not destined to have this car running correctly

Anyone that owns a 944 Turbo knows that #5 is the only correct answer

[Tom]

My guess would be #6 -- something you've touched a dozen time without realizing it was leaking and/or wasn't installed correctly. Nearly every time I'm convinced I have a physics-defying, one-in-a-million problem, it turns out to be something predictable and common. It's human nature to overlook the ordinary when on a quest to find the extraordinary.

Philosophy aside, check for hidden cracks/slits in the couplers, hoses, and j-boot. They can be sneaky.

[chrischrischris]

To OP: Did you fix it?

[NCGermerican]

To OP: Did you fix it?

........sort of. My next video will post tomorrow or Wednesday. Bottom line, I'm an idiot and was able to find one issue, but it didn't solve all the problems.

[chrischrischris]

Didn't Brent (Edredas) mention in a livestream he had an issue with a car that had a new wiring harness? I think he couldn't find anything actually wrong with the harness but since troubleshooting was going nowhere he had no choice but to go back to a stock harness.

[NCGermerican]

Didn't Brent (Edredas) mention in a livestream he had an issue with a car that had a new wiring harness? I think he couldn't find anything actually wrong with the harness but since troubleshooting was going nowhere he had no choice but to go back to a stock harness.

As a matter of fact, he did and I actually know the owner of that 86 944 turbo. Turns out there was a short in the harness and Kroon sent a new one.

My issues are the following:

1) Low manifold vacuum
-cold start at 10 in HG
-when engine reaches operating temp, vacuum increases to about 15 in HG
-normal should be around 18-20 in HG
-This has been an issue for over 2 years and there was a stretch when the car ran just fine with those vacuum readings

2) Lean condition at all times
-I found the source of this issue and it was my fault/mistake. I go into more detail in my upcoming video to be posted in the next few days.

3) Lean condition during warm start, open loop only
-This issue started happening about 2 months AFTER I replaced the short block in August of 2025
-AFM readings of 18+ on warm start, but resolves when entering closed loop (o2 sensor corrects fuel mixture)

[AudiSport]

What's your idle speed? I found that a slightly high idle also doesn't produce a lot of vac when tuning my MaxxECU.

[Tom]

Didn't Brent (Edredas) mention in a livestream he had an issue with a car that had a new wiring harness? I think he couldn't find anything actually wrong with the harness but since troubleshooting was going nowhere he had no choice but to go back to a stock harness.

As a matter of fact, he did and I actually know the owner of that 86 944 turbo. Turns out there was a short in the harness and Kroon sent a new one.

My issues are the following:

1) Low manifold vacuum
-cold start at 10 in HG
-when engine reaches operating temp, vacuum increases to about 15 in HG
-normal should be around 18-20 in HG
-This has been an issue for over 2 years and there was a stretch when the car ran just fine with those vacuum readings

2) Lean condition at all times
-I found the source of this issue and it was my fault/mistake. I go into more detail in my upcoming video to be posted in the next few days.

3) Lean condition during warm start, open loop only
-This issue started happening about 2 months AFTER I replaced the short block in August of 2025
-AFM readings of 18+ on warm start, but resolves when entering closed loop (o2 sensor corrects fuel mixture)

1. Starting at 10 cold and going to 15 warm is low, but not terribly so. Stock cam? Pretty hard to get 18+ at stock idle levels. What is your idle rpm? On my car, the vacuum goes down at lower idle rpm levels. I bumped my idle to 880 (see chip tuning guide) and the motor is just happier in every way and I now see vacuum of 18+ when fully warm. I'd start capping things off to see if something bumps the vacuum... Do you have a cat? Or collapsed downpipe? Head, valves, and cam all in good shape? Probably something simple but worth considering those other things that can prevent the creation of vacuum, and not just things that prevent the retention of vacuum.


2. Sounds like I was right with my #6 option.


3. Did you test the DME temp sensor? Any other changes leading up to this, like new chips?

[Tom]

What's your idle speed? I found that a slightly high idle also doesn't produce a lot of vac when tuning my MaxxECU.

Interesting, that's not my experience with the factory (and F9) DME, at least within a narrow 100rpm range. That said, the stock DME uses timing for small quick rpm changes which might explain the difference.

[NCGermerican]

What's your idle speed? I found that a slightly high idle also doesn't produce a lot of vac when tuning my MaxxECU.

My idle is pretty spot on (840-900) as per the ODB+ app from Focus 9.