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Bad idle e30 325 -89?

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    Bad idle e30 325 -89?

    Hello.

    Have a problem with my BMW e30 325 -89 (catalyst)
    When the car is cold so idle is very poor, it is around 500-1000 and the like skips.

    But after about a minute or so will idle a little better, does anyone know what could be wrong?

    It runs good and everything else.

    Had loose my spark plugs and they were wet (petrol) seems like the car will read a little more petrol too but am not sure when the fuel gauge is not 100%

    Grateful for help / Jimmy
    E30 325i M-Tech ll <3 :twisted:

    #2
    Are all the vacuum hoses properly attached? Mine did that when I first bought it, but then I noticed that one came loose so I fixed it and now it mostly idles normally. It's always us guys with the eta models having idle problems. :loco:

    If that's not your problem then I can't really help because I don't know anything useful about cars.

    Comment


      #3
      Yes i have checked all the vacuum hoses :/

      it may be the water temp sensor?
      have read that many have had the same problem, but that the sensor can do stuff like that worries? :/

      lambda sensor may also haunting?
      tried to disconnect the connector to my idling engine but then nothing happens?

      / jimmy
      E30 325i M-Tech ll <3 :twisted:

      Comment


        #4
        Welcome to the forum Jimmy. I'm going to bump your thread hoping someone more knowledgeable than I will help you.

        Comment


          #5
          Idle or hard starting problems are most commonly caused by intake leaks and/or
          a sticky or defective Idle Control Valve (ICV). The only reliable method of
          locating intake leaks is to have a smoke test run on the intake and crank case
          and to test the brake booster with a gage and vacuum pump. The complete list
          of possible causes of an intake leak is:

          Intake boot
          Throttle body gasket
          ICV hoses & connections
          Brake booster, hoses, and connections
          Crank case breather hose
          Evaporative control hoses, valve, and expansion tank
          Fuel pressure regulator & hose
          Injector seals
          Valve cover gaskets & bungs
          Oil filler cap
          Dip stick o-rings
          Oil return tube o-rings

          While leaks in some of those can be found by inspection or by spraying carb
          cleaner on suspect areas, not finding leaks that way doesn't eliminate the
          possibility. Only a smoke test will really work.

          Once the possibility of intake leaks is eliminated, the ICV needs to be
          removed and cleaned with carb cleaner until the vane inside moves freely. When
          the ignition is switched on you should be able to feel vibration from the
          ICV. If no vibration the ICV is bad, there's a problem with its wiring or
          connector, there's a problem with the TPS, or the DME (or Idle Control Module
          (ICM) on an ETA car) is faulty.

          For the DME (or ICM) to control idle, the idle switch in the TPS must work
          correctly. The switch should close when the throttle stop is 0.030-0.060" off
          the idle stop screw. Hearing a click doesn't mean the TPS is working. Check
          with a meter or test light.

          The fuel system should be tested via the suite of tests in the Bentley manual
          as invalid rail pressure can be a contributor to idle and starting problems. A
          simple injector check is to pull the injectors, jumper the fuel relay to run
          the pump, and see if the injectors are leaking. You can also point the
          injectors into a towel, remove the coil wire, and crank the engine to see if
          all of the injectors appear to be spraying in a similar fashion. The best
          approach to possible injector problems is to have the injectors cleaned and
          flow tested. Since raw fuel can or will be released in these tests, have a
          fire extinguisher handy.

          While a bad check valve in the high pressure pump can result in longer than
          normal cranking, if the fuel system is working as it is supposed to the rail
          will reach normal pressure in a few turns of the engine. A weak pump, clogged
          filter or leaking FPR in conjunction with a failed check valve can result in
          longer cranking and/or idle poroblems.

          The O2 sensor can be a contributor to idle problems. The O2 sensor is a
          scheduled maintenance item with a useful life of no more than 100k. If the
          sensor has that mileage or more (or is of unknown age), replace it.

          The AFM can be a contributor. If the vane doesn't move freely or the
          resistance track is worn the DME may be receiving invalid data from the
          AFM. And if someone has fiddled with the bypass air adjustment the DME may be
          unable to stabilize idle. The bypass air adjustment should only be adjusted
          per the procedure in the Bentley and with an exhaust gas analyzer. And even
          then everything else associated with engine management has to first be
          operating properly. If the AFM becomes a suspect, replacement with a good used
          unit is the best approach.

          Improperly adjusted or malfunctioning valves will affect idle and starting. As
          can compression issues from ring or cylinder wear. A valve adjustment is
          called for every 15k. A useful diagnostic is to run compression (dry and wet)
          and leak down tests on the engine. Aged ignition wires, plugs, distributor
          cap, or rotor can cause problems. Insulation does break down with time and
          heat. And since the youngest E30 is going on 20 years old, if the ignition
          system is original or the plugs are old replacement is indicated.

          Although not usually a problem, a bad DME temp sensor is a possibility. That
          generally won't cause an unstable idle, but can cause hard cold or hard hot
          starts and/or a rough idle. As can problems with the timing reference
          sensors. Although not commonly encountered, a bad harmonic balancer on an
          M20B25 or M30 engine will cause problems.

          When all other possibilities have been eliminated and idle or starting
          problems persist, replacement of the DME, or if applicable the ICM, is
          indicated.

          In many cases the cause of problems will be a combination of factors. So it is
          important to test and repair all of the possible causes.
          The car makes it possible, but the driver makes it happen.
          Jim Levie, Huntsville, AL

          Comment


            #6
            Thanks, great post! Currently troubleshooting some of this stuff so this is really helpful!

            Comment

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