My 440 GLT auto (1991/1992) runs badly after the engine is started. This is worse when the engine is warm, but is always present. For a minute or so there is no power and the engine backfires slightly (a popping noise rather than an explosion). I have monitored the Lamda Sond O2 sensor signal and the poor running occurs before the meter needle starts to swing. Once the sensor is feeding back the car runs fine.

This might point to an failure of the car to run in open-loop mode and disconnecting the O2 sensor confirms this possibility by producing the same symptoms, no accel and popping noises!

The voltage on the ECU lead for the Lamda sensor signal, when the sensor is disconnected and when it is connected but not yet up to operating temperature is 1.8v. I expected this to be 0.45 - 0.5 volts from the theory books I have read, but I do not know what it should really be on the Siemens Fenix 3B system fitted to this car. If anybody knows what the voltage should be I would appreciate knowing. At present it appears to be set at a seriously rich value that might be causing the injection system to run weak open loop.

The Haynes manual says that the B18FP engine has no adjustments and suggests I check for air leaks/gaskets etc. I have checked the connections to the inlet manifold and all seem OK. If anybody has any ideas how I can get the engine running smoothly in open loop mode, so the O2 sensor does not have to work as hard, I would appreciate hearing from them.

The car is dangerous to use in its present state as it crawls along at 10mph for the first minute or so after starting the engine!

Philip