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  1. #1
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    Symtoms of bad Coolant Temp Sensor

    My 1989 325i has some intermittant drivability issues. It sometimes gets a bit of a hesitation/stumble under moderate acceleration. It also has been getting crappy mileage (sometimes under 15 mpg by the computer). When I have this problem, the CEL does not always come on. I have, however, checked the codes and got 1223 (Coolant Temp Sensor). What would you expect the symptoms of a bad Coolant Temp Sensor to be? Could this cause my engine managagement chip to pump too much gas into my cylinders leading to the drivability problems (too rich?) and the bad mileage? Any other symptoms I should expect?

    Thanks!


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    The ECU adjusts mix based on coolant signal

    These cars are very sensitive to this signal. Your car could be stuck in cold start mode with a bad sensor (or connection) and running very rich. You should just replace it as they are cheap about $20 or less. Also clean the contacts and check the wires to make sure you have a good connection as the ECR senses resistance on the circuit.

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    Bad connection = high resistance

    High resistance on the CTS is telling the ECU that the engine is cold, enriching the mixture. Check the wiring first. If it is good, check the CTS. It should have a resistance of 2200 to 2700 ohms at 68 degrees F. It should be 300 to 360 ohms at engine operating temp (temp gauge centered).John
    88 ///M3 Cinnabar
    84 318i Black

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    BJSlagle
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    Maybe you can help me as well

    I've been having problems with my coolant temp as well. When the car is idling, the temp will rise to almost normal temperatures, always a little bit cooler than normal. Whenever in normal driving conditions it remains only a little above the blue, or even sometimes lower. Without any other information could you tell me something? I recently just drove some 60 highway miles and really noticed it, before that its just been short trips.

    Brian
    88 325is

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    Re: Maybe you can help me as well

    Unfortuantely, I won't be able to provide much help on your problem. I think the sensor that I'm getting a code about is different than the sensor that feeds the temp meter in the car.

  6. #6
    Neil
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    Re: Maybe you can help me as well

    BJSlagle -
    Your problem (which I understand to be that the engine seems to be running cold) sounds more like a problem with the thermostat (broken or worn or removed) than one involving the coolant temperature sensor. Try replacing the thermostat with a new unit - it's one of the least expensive parts under a BMW hood.
    Neil

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