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HOMESERVICE MANUALSSAAB1987900 BASE, 2D HATCHBACK, 2.0 J, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMFUEL INJECTION SYSTEM - CIS (8-VALVE)PREPARATION FOR LAMBDA SYSTEM CHECKSLAMBDA SYSTEM OPERATIONAL CHECK & ADJUSTMENTNOTES
1987 Saab 900 Base, 2D Hatchback, 2.0 J, Automatic

Lambda System Operational Check & Adjustment: Notes

1987 Saab 900 Base, 2D Hatchback, 2.0 J, AutomaticSECTION Notes
  1. Remove fuel pump relay and connect jumper wire across sockets corresponding to terminals No. 30 and 87. Remove plug at airflow sensor (if equipped). Turn ignition on.
  2. Frequency valve should operate, making buzzing noise. Dwell meter should indicate 45-65 degrees. Disconnect wire from oxygen sensor and touch wire end to ground. Readings on dwell meter should rise. Ground one end of 1.5-volt flashlight battery. Touch positive end to sensor wire. Readings should drop to less than 15 degrees.
  3. On models with throttle enrichment switch, operate throttle. Readings should be higher at idle or wide open throttle.
  4. If engine is cold, enrichment switches will be closed. Disconnect lead at temperature sender. Readings should drop slightly. If engine is hot, connect temperature sender lead to ground. Reading should rise.
  5. If starter enrichment relay is used, disconnect high tension lead at coil and crank engine. Readings should rise above normal level. If vacuum switches are used, apply vacuum to switch and note readings. Level should be higher with switch closed, and lower with switch open.
  6. Connect oxygen sensor and start engine. With cold engine, dwell reading should be stable. When engine warms up, meter needle should fluctuate 10-20 degrees. It may be necessary to run engine faster than idle to heat oxygen sensor to create needle fluctuation.
  7. Connect CO meter to exhaust test point. With oxygen sensor disconnected, reading should be stable on dwell meter. Note CO reading. With sensor lead grounded, reading should rise and CO should increase. With lead connected to flashlight battery, reading and CO should decrease.
  8. If dwell reading does not rise with sensor grounded, check sensor wiring. See ELECTRICAL TESTING in this article. If wiring is good, replace control unit. If dwell rises, but CO does not, check frequency valve and wiring. See ELECTRICAL TESTING. Replace if needed.
  9. If dwell does not decrease with battery connected to sensor lead, check sensor wiring and replace control unit if wires are good. If dwell decreases but CO does not, check frequency valve wiring and replace valve if wiring is good.
  10. Adjust CO to rich level (3%) with oxygen sensor still disconnected. Reconnect sensor. Reading should drop at least 1%. If not, replace oxygen sensor.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.