924Board.org

[ideola]

I have the S1 factory manual, but the 941 has an S2 TPS. I need to know what to check and how to adjust the TPS. I'm continuing to investigate a super-rich condition from part-throttle to WOT on the 941, trying to determine if it's merely the S1 WUR, or if something else is going on in the enrichment circuit. I'm currently running with the stock narrowband O2 sensor disconnected. I have a UTCIS-PT that I am planning to install, but I want to eliminate as many potential issues with other parts of the CIS before installing it.
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erstwhile owner of just about every 924 variant ever made

[Cedric]

[ideola]

The S2 has the big single TPS arrangement very similar (if not identical) to the early 2.5L motors (the throttle body core itself is identical), whereas the S1 had dual microswitches. I earlier confirmed that the wiring was redone correctly to convert from the dual microswitch to the single TPS setup, but what I haven't checked is whether the TPS itself is oriented correctly, and what the voltage outputs should be at various positions.

The S2 TPS has elongated slots in its mounting bracket that would allow the switch to be activated a bit differently relative to the throttle butterfly. But you can't adjust this without completely removing the throttle body, as the TPS is mounted with two small flat head screws that face the intake runners. No room to get under there. I want to make sure I have the TPS physically oriented correctly, and I also want to confirm that the electrical function is doing what it should. I don't have any indication of what the electrical readings should be, so I was hoping someone would have this information so I can test it's function.

I currently have the mixture adjusted so that the car idles at 14.0 AFR with the narrowband lead to the Lambda system disconnected. If I set the mixture any leaner, it backfires on decel, and won't hold idle correctly especially for the first 10-15 minutes of running, so I don't think I can go any leaner on the mixture. While driving, I am getting somewhere between 11.5-12 AFR on light throttle (like cruising on a flat road at 50-70 MPH, for example, no boost, ~5 Hg vac). As soon as I press the throttle, even slight, it goes to 10.5, and by 60-70% throttle, the AFR displays full rich. On off-throttle full vac decel, I'm getting somewhere between 12.5-13.5 AFR. Fuel economy is horrible, like 15 MPG (I always run Mobil 93 Octane). All this tells me I'm running way too rich.

I will also be testing the control and system pressures again on the WUR, but the last time I did this (last year), it was within spec. Will be double checking, of course. I just want to eliminate any variables possible before introducing the UTCIS into the mix (pardon the pun).
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erstwhile owner of just about every 924 variant ever made

[ideola]

Maybe this is what I'm looking for re: the electrical part of the question?
http://www.924board.org/viewtopic.php?t=25098

[Joes924Racer]

Dan, Cedric this is a good
post to print off. Say -
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[Rasta Monsta]

Take a closer look at the materials I sent you a while back. . .the procedure is in there. IIRC, it is accurately described by Paul in your link. If you look at the wiring diagram, you should be able to test the idle switch continuity with the TB installed. . .find which of the two wires leads to Term 2, and check it against any ground (should be white with either black or blue stripe, IIRC).
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Joes924Racer]

- I dont have to worry of s-2 issues. Though good
stuff 4 a rookie like me to read.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.