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89 200 Intermittent Miss, was 3 -Wire O2 sensor


If your 89 200TQ has the early MC engine with a single
knock sensor  (before VIN # KN038262) with the MAC11 ECU
then it is possible that the ECU is detecting a fault in
the system (defective knock sensor possibly?) and retarding
the timing. This can make the car stumble or hesitate on
acceleration. The MAC11 ECU does not remember fault codes
after you turn off the ignition which may explain why it
works ok after re-start.

The later dual knock sensor MC engine with the MAC14 ECU
has a static RAM that is used to store fault codes even
after the ignition is shut off. 

When the car begins running poorly, you may want to leave
it running and then pull out the fault codes (if any) as
outlined in the Bentley Manual. You could have other faults
that are causing the poor running, i.e. air temp sensor,
coolant temp sensor, throttle switch, RPM or TDC sensor
etc. Code 4444 indicates that no faults  were detected. 

Regarding the 3 wire O2 sensor question:
John Karasaki at johkar@teleport.com replaced the O2 sensor
in his V8 Audi by using  (I believe) a VW 3 wire O2 sensor
and then splicing the connector/wiring from the V8 harness,
you may want to check with him.

Scott M.