Re: its an 89 740 GL, has the Bosch LH2.4 control system. B230 engine, 4-cyl, gas, fuel injection.
In Park or Neutral, the engine/acceleration is just fine. But when you accelerate from a stop, usually right as it shifts into 3rd, the engine just drops down to idle speed. Pushing the gas does nothing at all, you have to release the gas pedal..then you have control of engine speed again. Also, it is getting extrememly poor gas mileage. But there is no black smoke, and all of the spark plugs look normal and identical...no heavy black soot deposit.
No codes are being set at all.
I was told that it was a bad AMM sensor, and the car is going into limp-home mode. Don't think so now! As a test, I disconnected the AMM...then with the car parked, there is no idle at all...it dies if you do not hold gas pedal. ALso, it ran roughly at idle and above. This also caused the chk engine light to come on, proving that the ECU is sensing faults.
I am going to check the fuel rail pressure. If that is OK, I don't know what it can be but a bad ECU. The car must be running extremely rich to burn gas like it is, yet the ECU isn't reading that from the o2 sensor and setting a fault code.
This is very bad if it is the ECU, as I think they cost around $400, and probably not returnalbe once used. So I pay $400 to get and sub in an ECU, and it doesn't fix the problem....I am screwed! Advice? Know of a cheap source to get a rebuilt ECU? Thanks for the advice.