Simi rough idle

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  • SterlingMetE30
    Wrencher
    • Mar 2014
    • 229

    #1

    Simi rough idle

    Hey guys. I have had my car for a while now I have done new plugs, wires, cap and rotor. Cold or warmed up it has a rough idle. From the exhaust end it seems like a cylinder or two aren't firing completely. I haven't done compression tests. I was told the car had a 75k b27. Although I think I might be clogged injectors or o2 sensor. I doubt either were change with the engine swap.
  • NoM54me
    Advanced Member
    • Feb 2014
    • 158

    #2
    Coolant temp sensor? Check the CTS connector too, if it has the inline resistor, it may be bad. Just pull it out.

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    • SterlingMetE30
      Wrencher
      • Mar 2014
      • 229

      #3
      Originally posted by NoM54me
      Coolant temp sensor? Check the CTS connector too, if it has the inline resistor, it may be bad. Just pull it out.
      Perhaps the cts? My temp never reaches half ever. But idk how it would effect idle? Lay some light on me please.

      Comment

      • NoM54me
        Advanced Member
        • Feb 2014
        • 158

        #4
        Coolant temp sensor--not to be confused with temp sender, that goes to gauge cluster. The CTS essentially tells the ecu how much fuel to inject based on the engine's operating temp at any given time. If it's bad, the engine will run a little rich and rough like a misfire. Some, but not all, have a dealer-installed resistor in the CTS connector which was intended to cause the engine to run a bit rich anyways. These go bad too, making the CTS basically functionless. When replacing your CTS, pull back the rubber sheath on the connector to see if you have one, it may be a bit further up on the harness too. Cut it out, and just splice the wires together. Your gauge should indicate full operating temp as exactly halfway, or it it's like mine, "normal" is midway between the middle line and the one to its left, so a bit cool.

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        • SterlingMetE30
          Wrencher
          • Mar 2014
          • 229

          #5
          Gotcha. I will check it out when it gets light out again. I wouldn't mind getting better better injectors. Besides I want to do the I conversion on my car.

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