Automotive Manual PDF

The following actions were taken in order of time needed to perform them…
Verified that the plug wire was transferring energy to the #1 plug by removing (from the spark plug, not the distributor) it and holding it close to the engine block. The presence of a spark at regular intervals demonstrated that the wire was acceptable. Also the ignitor and distributor were OK because the other 5 cylinders were firing normally. After changing the #1 spark plug, the symptom remained. This verifies the presence of a spark in the cylinder.
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850 turbo uses a Motronic 4.3 control system, which has a single Electronic Control Module (ECM) to control fuel injection and ignition systems. In addition, Motronic 4.3 control system incorporates an on-board diagnostic function. Signals from various sensors are monitored continuously. If certain signals are lost or become faulty, ECM will adopt fixed substitute values (limp-home mode) to enable vehicle to be driven for certain failures. Substitute values can be adopted for Engine Coolant Temperature (ECT) sensor signal, Throttle Position (TP) sensor signal, Mass Airflow (MAF) sensor signal, and oxygen sensor (HO2S) signal. See Fig. 1.
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