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Cold start, rough idle

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  • Cold start, rough idle

    I've been looking all over for vacuum leaks and haven't found any. When it starts up, sometimes will die right away if it's been a real cold night and the garage is around 40-45 degrees. My temp. gauge doesn't read for a few seconds, them jumps into the blue, but it used to kick right on no matter what. Thermostat going bad, sending the wrong info or ???
    58k miles and change

  • #2
    You did look through the FAQ on rough idle, right? Maybe your ECU temp sensor (not the one for the dash gauge, the other one) is bad or disconnected?

    Does the car run OK when warmed up?


    • #3
      Mine used to have a real crap idle, it was just the CO was way too rich, now she is sweet, a cheap fix.

      '90 M3
      '58 Austin Healey Sprite
      '02 Suzuki SV650S


      • #4
        Mileage on cap& rotor?
        Mileage on Plugs?
        Mileage on Plug wires?
        Mileage on Lambda sensor?
        Last time it had a tune up?



        • #5
          Not the T-stat. It stays closed untill the engine is warm then opens to let the colder coolant into the engine. Possibly stuck open. Does it take a long time to warm up? This should not effect cold start up idle issues.

          "Never lift"


          • #6
            All ignition components are less that a year old, and have about 1,000 miles on them. Was tuned at the same time everything else was replaced including a valve adjustment.

            It doesn't take long to warm up, atleast nothing which seems out of the ordinary.
            58k miles and change


            • #7
              If you have a helper turn the ign to "ON" and you have your ear close to the ICV or a finger on one of its hoses, can you hear/feel a buzzing?


              • #8
                The sender for the coolant gauge and the temp input to the ECU are two different sensors.

                Sounds to me an awful lot like the temp sensor for the ECU, or the wiring. That is the one with the blue on the passenger side of the motor at the front. The sensors go bad or the wiring going to the sensor shorts. That would cause poor running when cold.

                As for the temp gauge . . . does it jump around at any other time? The screw on the back comes loose causing it to jump around sporadically.
                "E30 M3 . . . it's the perfect toy for an upscale closet wild man." Car and Driver, 1988 M3 Road Test