Greetings fellow Bricksters, I'v been working on this '89 240 (235.00 miles) with a rich running problem.
The car is definitely running rich, the o2 sensor read .55v at cold start then climbs to approx. .9v and then stays there. After a short while it throws the CEL.
The coolant sensor checks out OK as does all the connections at the ECU (power, ground, voltage and resistances.
I tried swapping the fuel pressure regulator with one from an "88 240 (lower pressure) with no difference.
I have two codes that I think are false: #312, missing knock sensor signal and #213, throttle SW full-throttle contacts misadjusted or shorted to ground.
I swapped the knock sensor with a used one and measured the .7v at ECU pin #28 ;then same code, installed NEW knock sensor and no change.
Tested the throttle switch and wiring and all is good but still get the code #213
Still get random fuel codes #231, 113, 221
Tried swapping the AMM with an #007 from an "88 volvo, did not idle at first then ran rich.
So I'm down to leaky injectors, bad AMM or bad ECU. I have rarely seen a problem with injectors which makes me lean to the ECU.
Have I missed anything else ??
Thanks
peter