924Board.org

[Roger]

While practially rebuilding my CIS system I had to replace the TECU (Throttle Enrichment Control Unit). I got a used OSCU (Oxygen Sensor Control Unit) that came with the TECU still attached. The original TECU would not richen the fuel mixture as the throttle was opened. Now the 2nd TECU has failed. Now the car runs extremly rich. The car runs the same with or with out the TECU connected.

I have a third TECU that I pulled from a junkyard. I installed it and the fuel mixture leans out and the car runs fine. I disconected it because I dont want to blow the only remaing one I have.

Any ideas. Is this just bad luck that the 22 year old used part failed within 4 months? Or is this a larger electrial issue.

I'm thinking that I need to open up all three and trouble shoot the circuit boards. All I have is a multimeeter I am hoping that I will be able to figure it out. Dad was an electrical engineer I will talk to him about it also.
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[Roger]

Turns out I did not have the wires correctly attached. The WOT TPS was conected to pin 6 not pin 7. I corrected this and now neither TECU works properly.

Can any one give me the pin out for the 12 pin connector on the TECU from the factory manual? Mine does not match the haynes. The most currious thing is that the WOT TPS is connected to a constant ground on the TECU. I found a 924 at the local junkyard that had the same wiring so I am confused.
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[Roger]

This is from a PM I got on Pelican. I thought that some of you might find it interesting. Any ideas or thoughts? Also my thanks to drew1.

Roger wrote;

The connector is numbered so it is easy to identify the connections. The actual pin out on my car has the following exceptions.

Pin 5 is a brown ground wire that is jumped from pin 11
Pin 7 is wt/bk going to the full load TS. I posted that it was previously connected to pin 6. I was wrong it was actually connected to pin 8.

If I pull the brown jumper from pin 5 and connect the wt/bk from the full load TS my wiring will match the factory manual. I knew the wiring was strange and I have played with it, but interestingly I found another 924 with the same strange wiring. I would like to check the part number on the oxygen sensor control unit and the throttle enrichment control unit. Do you have a PET?

[Roger]

Well this is the fourth time I have responed to my post. I may just let this one die but I have one last update.

I stoped by the mechanics today and he lets me look at the factory manual's. The 12 pin conector on my TECU my car is wired for the 81 turbo however the 8 pin connector has the wireing for the 81 N/A. Instead of the three TPS switches the 81 turbo used a potentionmeeter (sorry spelling probably wrong). With the potentionmeeter The full load TPS connection seemed to be used as the ground.

I rewired the car and the throttle resopnse is much better especially above 5000 RPM's.

It still runs rich but that may be a problem with the fuel distributor. I had rebuilt it and I noticed tha it is leaking. I spent tonight rebuilding a spare I got from the junkyard. I am starting to think that mechanical fuel injection was Fuzzy Logic from the beginning.
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[endwrench]

Keep us Posted Roger!
Seriously, this will make great info for the archives. Thanks

Todd

[924 turbo]

The 1981-1982 turbo doesn't use a potentiometer, but a three position switch encased in one unit. It functions very similarly to the three separate switches in the 1981-1982 n/a.

Also, if your car is experiencing poor throttle response above 3500rpm while warm, it's probably a mechanical problem, your O2 sensor control unit has failed, or the full throttle enrichment circuit in the TECU has failed.

The acceleration enrichment (not full throttle enrichment) unit only operates when the car is cold.
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Jon Furst

[coconutcowboy]

I am buying a set of parts cars if you need pparts let me know and i'll let you know if it is the correct part I can get for you.


look at my thread under general discusions. The thread is group purchase of 924's for parts.
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84 944 2.5l NA for sale.

80 924 w/ turbo nose/ m471 option/ ac and Pasha Interior. w/ bursch header and exhaust, stage 2 cam, Audi wur and tb

ricer's shall kneel before the mighty Porsche or unforgivable harm shall befall their engine blocks.

[Roger]

coconutcowboy
I really appreciate the offer, I will let you know.

924 turbo
Thanks for all the help on both threads. You have helped me make sense of the electronics. The mechanic told me it was a potentionmeeter, but your explanation makes more sense looking at the current flow diagrams. It does appear the full load sensor pin on the N/A is jumped to ground on the turbo and not on the N/A. I have rewired the pin out on the 12 pin connector to match the N/A. I basically disconnected the jumper from pin 11 and connected the full load TPS to pin 5.

I installed the rebuilt fuel distributor and it ran OK. No leaks however I had problems getting the car to idle correctly. I have three separate OSCU and three TECU. I will try each of them and see if the problem improves.

I think I have another problem though After I replaced the fuel distributor with the rebuilt unit durring warm up the air/fuel mix responded properly. After the engine warmed up it went full rich. I need to make sure that the air/fuel mix is correct, and sort out this wiring problem. I also need a CIS pressure test to rule out the WUR. It could also be an injector problem, but that is doubtfull.

In addition the car has run hot three times. It has reached the red zone for three or four miniutes. It has never boiled over though. I had to add a little less than 1/2 gallon of distilled water today. I am thinking head gasket (probably not), sticking thermostat, bad water pump, or possible leak. The fans are running properly. I am going to flush, refill and bleed the cooling system Saturday.
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[coconutcowboy]

part of keeping the 924 engine alive is periodically retourqing the head gaskets.

you may need to replace it if the PO hasn't.

when doing head gaskets first flush out system good then disassemble motor.

now is the time to replace all those obscure little coolant hoses and sensors / switches and thermo vac valves.

also a good time to replace water outlet gaskets, waterpump and t- stat.

also a good time to do timing belt and tensioner.

while head is off have it trued valves ground and guides knurled and new stem seals and cam seals installed. also replace injector inserts and orings.

If you have a dremel a little port matching to the gaskets on the head, intake and exhaust manifold would be a wise move for a little hp boost.

ONE other thing. replace fan switch and t stat with coooler units to start removing heat from the system early. an aftermarket hd radiator might also be in order. and don't forget to get a new radiator cap of the proper specs.

Sean Ross
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84 944 2.5l NA for sale.

80 924 w/ turbo nose/ m471 option/ ac and Pasha Interior. w/ bursch header and exhaust, stage 2 cam, Audi wur and tb

ricer's shall kneel before the mighty Porsche or unforgivable harm shall befall their engine blocks.

[positivesale]

Have you bled the system, and you just keep getting the same result? (still overheats)

If the car is running hot according to the gauge, be careful. Do you know the true temperature of the coolant, ,since the gauge could be wrong...If you keep bleeding the system, and the problem comes back over and over again, you may have a leak in the upper part of the system. This leak will not show, as since it is in the upper part there is no fluid there. I had a bleeder leak, but I did not know this until I poured water on it and saw bubbles. There's a possibility that the bleeder is bad on your car, but since they are plastic on the 924, I doubt it. Or there is a hole in the upper part of the system (a hose or the bleeder, or even porous metal somewhere).
Also the gauges can be bad or the temp sender can be bad. So if you think you are overheating when it's going into the red.. the real nightmare is that it may have already overheated before reaching the red! I don't know if this is a rare problem, but I did have this problem. Car overheated in the white section of the gauge. I thought the car was running cool, since it was in the white, and the internal heater core was blocked (stuck valve)! Good test (which I did think of at the time), is a meat thermometer to verify that the car really is overheating, and WHEN it really is overheating (so you can compare to your gauge, for verification)It could be that the car isn't overheating at all.. I've heard of people see the gauge go to red, but it doesn't actually overheat when they verify it with a meat thermo, or a new sender.. (meat thermo obviosly the cheaper route- plus even a new sender could be bad, have a bad ground, etc., you never know)
I still have to try my meat thermometer out, to see how accurate it is.. But I'm pretty sure they are if people use them to test meat!

The car can blow a headgasket without overboiling. It will overboil after you've blown the gasket sometimes. Sometimes it will overboil before you've blown. It can also blow, and never overboil or appear to be blown. Also another possibility as suggested to me by Nummbers once, was that a rag was still stuck in one of the hoses or joints, or the rad, if you were cleaning it or the PO did.
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82 931