CVambience

I can't figure this out. My S2 is a 1991 German model. I bought it used a year ago. The car has a 1989 S2 ECU #944.618.124.02 on board (It looked like someone replaced it. Isn't it so that the 1991 S2 should be equipped w/ a #944.618.124.05 ECU? Are there any exceptions?). Anyway, I recently bought a 1991 S2 ECU, but I am having hard time starting the car w/ it. Anyone have any clue what should be the cause? I bought it from Porsch-Apart in UK; they said that unit was tested OK prior to shipping. Isn't it strange that a 1991 S2 ECU doesn't work on a 1991 S2 car; instead, a 1989 S2 ECU works.

Eric
P.s. I bought the 1991 S2 ECU because I want to chip the car in the future. Most chips for the S2 are made for 90-91 cars.

AZS2

How do you know your car should have that "91" ECU? Are you getting your part numbers from US Specifications? I mean, your car is Euro-Spec and transplatted to Taiwan. Who knows what the history is? It could have a completely different motor, it could have been stolen and retitled. You should probably start by making sure the engine is 91 also. I would guess there is a serial number somewhere on the block that will date it.

CVambience

Good point. I will check. Thanks.

Eric

Ken D

The engine serial number should start with '42M' if it is a MY 1991 engine. An '89 engine will have a serial number starting with '42K'. All S2 engines are type M44.41.
It appears all S2s shared the same AFM, but had different fuel injectors and intake manifolds that changed over in MY 1991.
All this applies to ROW S2s.

CVambience

I just checked the engine#. It's 42MO4165; so, it should be a 1991 S2 engine. The VIN is WPOZZZ94ZMN401982. What else should I check? W/ this info, can someone explain to me why a 944.618.124.05 ECU not working on my 1991 S2?

Eric

Ken D

Have you opened the ECU? Did you install the EPROM chip (Promax)? If so, first ensure it is seated properly in the socket. That has caused issues before.

If you opened the box to replace the chip, did you run the car with the replacement ECU before you changed the chip (i.e. with the factory chip)? Did it start ok then?
You can always eliminate the chip as a problem by 1) ensuring it is properly installed & seated; if yes, then 2) switching it with the factory version and attempting to restart.

CVambience

I haven't open the ECU box. And it looks like it has never been open before; these metal pieces on the sides of the ECU box seem brand new. So I was testing the replacement ECU w/ supposedly stock chip.

Eric

manu4jc

This is an old thread but I had a similar problem so I will post the solution here in case it helps someone in the future.
The OP had a 1991 S2 engine running fine with a 89' S2 computer and when he used a 91' S2 computer it would not run.
I would bet the previous owner not only changed the DME to an 89' but also the injectors. 89' injectors (BOSCH 0280150811) are low impedance (2.4ohm), 91' injectors (BOSCH 0280155003) are high impedance (15.4ohm).
If you were to swap in a 91' DME and a set of 91' Bosch injectors you should be back in business.

jhowell371

I think you are right on target.

aussie944cab

As far as I've worked out that 89 use low impedance injectors but have resistors in series bringing the total impedance to around that of high impedance injectors, while i was playing with injectors in my 89 cab, I accidentally put low impedance injector in without the resistors and drove it around the block, didn't blow up the DME but ran rich, testimant that they are built tough, not like todays stuff

Arominus

There are a few other wiring changes in 91 as well, the way the A/C gets activated changes. We had to correct this to get the 968 swap working in my 89 S2 as the 968 carries forward the changes that happened in 91

sweetskillsrk

Good to know, thanks manu4jc. Can you just Ohm them out between the terminals to check and see which injectors they are? I pulled a set out of a 89 951 for a spare set for my 88 944, but after reading this I'm not sure they'll work. I know there's a lot of differences of course to the 951 engine, but I figured the injectors would be the same just tuned differently.

KEVIN ANDERSON

I have a 1991 944S2 Coupe. The 1991 version got the most advanced version of Bosch Motronic software of the time. The DME has 3 stacked chip boards. Yes it has completely different fuel injectors. They are very, very expensive as they were only used on the 1991 944S2. I had to get a performance chip made in Germany because I could not find one for a 1991 anywhere else. DMEShop24 was the shop, but he has since taken his website down. I also bought 944 Turbo Cup chips from him for my 1987 951. They are suppose to be the tune used in the Turbo Cup cars. A 50 HP increase above the 220 HP and the 250 HP Turbo S cars. They have been the best chips I have ever used in my 951 and I have used them all. A-Tune, M-Tune, Autothority, 951MAX and another MAF system that is claimed to be the best MAF system and the first to back engineer the software. My 951 runs the best with the AFM and the Turbo Cup chips. I'm not saying it has the most power with these chips, I'm just saying that starting, idling and driving, they are the smoothest and the engine runs without a stutter. A 1991 S2 engine can run fine with a 1989 DME and fuel injection system that matches the DME. I don't know if there is more to the picture than just using resistors for the injectors. The entire pulse loop can be slightly different. I know that I can't afford new fuel injectors, so until I get a DME from Peep, I can only send my injectors to Witch Hunter to get tested and cleaned. To me the S2 runs fine, but it could run a lot better, I just don't know it yet. My car was missing the stock air box when I bought it. It has an aluminum pipe and a cone air filter. I deleted the cat with a straight pipe. So with the chip, cone air filter and cat delete, it is a very fun car to drive and it is way more dependable and less moody than my 951. So that is my experience so far if it helps.