Date: Thu, 28 Jan 1999 15:58:58 +0000 From: Mark Sempers <mark_sempersnopsamorg.com> Subject: Re: 1989 9000S problem - really stumped!
Tom, I'm assuming that your car has the Bosch LH system given the vintage, I assume your saab guru has the ability to pull the check codes from the engine? If you have the later (v2.4) LH system, you can do this yourself with a bit of wire - again, I'm not sure if you have the 2.2 or 2.4 LH, I think it would be 2.4 on that year. If the injection time is so long, I'd assume that the ECU is registering some error codes - internally if not displaying the CheckEngine light. It would be interesting to see what they are - is it only too rich at idle, elsewhere in the range, or at WOT? Do you have any flat spots etc on throttle? It would also be very interesting to know exactly what your mech has tried to fix this. (side question occurs to me - does yours have the lambda(O2) sensor in the exhaust (screwed into the pipe, roughly under the steering rack) - this is (AFAIK) what is used to detect too rich conditions etc, and is also used as a trim - pre lambda cars just use a uncompensated MAF/Fuel mapping. It's likely (I think) that your car is running rich across the whole range, it's just a lot more noticable / unsustainable at low revs. I'm guessing that you don't have lambda, 'cos your mech says there are no faults - lambda would scream blue murder under those circumstances (if you do have lambda, I'd suspect / check that) This leads me to think the Mass Air Flow meter (MAF) is providing incorrect readings.. this can be for a few reasons : 1) MAF sensors (some?) have a compensating screw for adjusting the mixture in the side of the housing. Doubt this... 2) Wire goes high resistance (w/o breaking) - you can imagine the effect, again, this will probably be evident across the whole range. 3) Contact to the MAF goes poorly - the ECU seems somewhat reluctant to log a "MAF is missing" error, mostly you see mixture errors - too lean at idle, too rich at idle, too lean, too rich (general running) etc. (assuming you have lambda to detect it), I'd suggest a can of contact cleaner on this as the first move - it's cheap, and easy to try! Other things to try beside a close inspection of MAF and the wiring to it, moving farther afield, I'd check out the throttle position sensor with a multimeter - make sure that the throttle closed switch is operating properly, it should open just as the throttle hits the stop. HTH, feel free to come back with more details... - Mark. > > 1989 9000S 140000 miles > Stalls under no throttle, such as when coasting up to a stop sign, > etc. Under constant throttle, runs fine. On the highway when you > allow it to coast and then accelerate, there is a short jerk, then the > car accelerates OK. > Running very rich, injection time is 12ms instead of around 3 ms. > My SAAB guru and I are both stumped since he has run all the > diagnostics he can and they all say the car is running fine. Switched > controller units, same problem. Can't believe that 2 units would > produce the same fault. All mechanicals, such as timing, plugs, > compression, are OK. Could find no shorts, etc. in the wiring > harnesses. All suggestions welcomed because we are stumped. > TIA, Tom