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Runs rough when started warm, but runs well when started cold 200 1992

I have a 1992 Volvo 240 Wagon 5-Speed that when I start it first time every day when it is warm outside it runs rough, but smoothes out some when engine is hot. When it is cold outside and I start it up it runs fine.








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    Runs rough when started warm, but runs well when started cold 200 1992

    Hi,

    My first guess would be the coolant sensor is a little off on calibration if you had the opposite symptoms.

    The next one would be the fuel pressure regulator leaking by it diaphragm.
    The fuel lays in the intake manifold or the line to it from the FPR.

    Rich in coldness is ok but not warmed up or up to operating temperature.

    Phil








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      Runs rough when started warm, but runs well when started cold 200 1992

      I agree with Phil. If the ECT is incorrectly telling the ECU that the engine is stone cold then you may be getting excess fuel during warm cranking. Like Phil says, suspect the ECT, rearmost of the two temp sensors under the intake manifold. Do you have a cold start injector? If so, before beginning an attempt to start warm, disconnect the injector first. If it now starts normally then that would help confirm this theory. If you don't have a cold start injector then you'll have to start with normal diagnosis of the sensor. There's tips in the FAQ here and a number of recent posts with resistance readings for testing at the ECU connector. Note that if you're checking at the connector then yours will likely be the later, two sided temp sensor that uses the block for ground. If it was fuel starvation, it would more likely be a cold start problem.
      --
      Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now







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