Cold Driveaway Diagnosis For 1981-83 900, 900S, Turbo
COLD DRIVEAWAY COMPLAINT DIAGNOSISModel Years: 1981-83 900, 900S, Turbo (see p. 9 for 1984-85 cars)
Symptoms: Tendency to stall when first put into gear, particularly 900 and 900S. Hesitation on acceleration for the first minute or two of operation, possibly accompanied by backfiring into the intake manifold.
Diagnostic and Repair Details
1. Perform the steps required to check for a Cold Start Complaint. Do not skip any of these steps. Cold engine only.
- Check rest position of air flow sensor plate.
- Check for intake air leaks.
- Check auxiliary air valve (cold engine only).
- Measure and adjust the line pressure, if necessary.
- Check the cold control pressure and correct, if necessary.
- Check the cold start circuit.
2. Check for acceleration enrichment during warm-up (cold engine only).
- Connect a test light between the cold start injector plug (brown wire) and ground. Do this through the back of the plug, do not remove the plug from the cold start valve. The engine must be below 113~ F.
- Start the engine. Every time the throttle is opened rapidly the test light should flash briefly. If inoperative check:
a. Power to the pressure impulse contact.
b. Vacuum at the impulse contact.
c. Mechanical function of the pressure impulse contact. Connect a vacuum pump and a pressure gauge (Turbo boost gauge 83-93-514) in series with the impulse switch. Attach a continuity tester to the electrical contacts of the switch.
Draw vacuum until you reach at least 0.3 bar and release it rapidly and note if there was a brief moment of continuity at the electrical contacts. Repeat the test several times. If continuity cannot be obtained, replace the switch.*
Impulse Switch P/N 93-15-953
3. Install the service kit to improve driveability on certain M82 and M83 naturally aspirated vehicles.
Driveability Kit P/N 85-46-921
The service kit may be fitted to specific naturally aspirated M82 engines and all M83 naturally aspirated engines having Lambda Electronic Control unit P/N 93-62-617 (Bosch No. 0280-800 054).
This kit cannot be used on M82 vehicles with alternate "M81" Lambda systems identified by Lambda Control Unit P/N 93-37-718 (Bosch No. 0280-800 035), produced within VIN Serial No. ranges C1012287-29974 and C2006539-10800.
Complete installation instructions are supplied with the Service Kit. Instructions were also supplied in S.I. 06/84-692 (Bound Supplement No. 4).
4. Check the PVS valve of the EGR system (all M81 vehicles, all M82 naturally aspirated, all M82 Turbos without APC). A defective PVS valve can cause poor driveability as the engine is warming up.
Check the PVS valve by blowing through it. Below approx. 112~F the valve will be closed. Above this temperature the valve will be open.
Replace the valve if defective.*
PVS Valve P/N 93-14-162
5. Connect a Saab Pulse Relation Meter (83-93-597).
Start the engine and allow the car to fully warm up (radiator fan should cycle on a few times). Note the pulse relation reading. The pulse ratio should be 45-55% for optimum driveability. Adjust if necessary.
Pulse Ratio (engine warm): Checking and Setting - 45-55%
(Note: Any reading from 10-90% is accceptable for exhaust emission compliance.)