Announcement

Collapse
No announcement yet.

325 eta surging idle (I've done a smoke test)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    325 eta surging idle (I've done a smoke test)

    I have had a fluctuating high idle for a couple months now. It wasn't that bad after I changed the o2 sensor. It mainly just idled around 1100 with an occasional bouncing. The other day I tried cleaning the ICV out real good and that made the surging idle more pronounced (constantly bounces between 900 and 1500 when warm). When I unplug the ICV, the idle goes even higher.

    Of course, I thought of vacuum leaks, but the shop I took it to said the smoke test yielded nothing.

    So, my question is, what are the chances of my ICM being the culprit? Are there other things I should be looking into?

    EDIT: 1986 325
    Last edited by Saeulf; 04-14-2013, 03:26 PM.

    #2
    have you tried useing another icv? it could be a combination of your icv, maf, tps. our cars are old and these idle things drive us all a little nuts. mine was the combination of all i mentioned.
    sigpic

    Comment


      #3
      The first item in what follows has been done (assuming the smoke test was done properly). Now work through the other possibilities.


      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


        #4
        Wow Jim, that is a great write-up on intake problems!

        I'm commenting here so I can find it easily by searching for threads I've posted in.

        Comment


          #5
          What I am most curious about is why a freshly cleaned ICV would amplify the problem? The high idle wasn't bad until I cleaned it thinking I was doing the car a favor... perhaps the ICM is bad and now it has more data to misinterpret? I will attempt to get another ICV to try. Is there an easy way to tell if it is working correctly?

          What exactly would a bad ICM do?

          Thanks for the grocery list, jlevie :p
          I was slowly working thru some of that stuff when I stumbled upon my current question.

          Comment


            #6
            what i had notice about m20 is that the tps is on the bottom so any juice you throw in through the intake end will drip down to the tps, messing it up.
            Bought parts from me before? leave your feedback here

            Comment


              #7
              Idle Control Valve. Drill a quarter inch hole in a penny. Pull the hose on the AFM side of the ICV. Put the penny there and replace the hose. Your idle should even out to about 600RPM. This is a temporary fix until you buy a new ICV.

              Comment


                #8
                Thanks for the input, all.

                Currently, I am awaiting a throttle body gasket so I can do a thorough cleaning. I noticed the TPS is soaked in oil, so I think it wise to take the opportunity to clean it out.

                I haven't rulled out the ICV, yet. I want to say it works, because the idle gets worse with it unplugged, but we'll see...

                Comment


                  #9
                  When you clean the ICV's it is possible to get it to clean if that makes sense, which would cause the hunting to be worse. I bypassed the whole ICV system and left the ICV hooked up. That way I could have it idle without adjusting the throttle plate and throwing the tps sensor all to hell.
                  sigpic
                  85 swartz/metallic 325E
                  84 alpine 325E
                  85 zinnoberot 318i/R.I.P
                  84 Bronzit 318i/sold
                  purchase feed back here=http://www.r3vlimited.com/board/show...82#post3535282

                  Comment


                    #10
                    Or you can just permanently fix the ICV

                    http://www.socale30.com/theforum/vie...php?f=1&t=6029

                    1991 325iS turbo

                    Comment


                      #11
                      ^um it says it only works on i cars right at the beginning not eta, so no help buddy^
                      sigpic
                      85 swartz/metallic 325E
                      84 alpine 325E
                      85 zinnoberot 318i/R.I.P
                      84 Bronzit 318i/sold
                      purchase feed back here=http://www.r3vlimited.com/board/show...82#post3535282

                      Comment


                        #12
                        Originally posted by crazyman View Post
                        ^um it says it only works on i cars right at the beginning not eta, so no help buddy^
                        Didn't realize it was for an eta my mistake, pal.

                        1991 325iS turbo

                        Comment


                          #13
                          Originally posted by crazyman View Post
                          When you clean the ICV's it is possible to get it to clean if that makes sense, which would cause the hunting to be worse. I bypassed the whole ICV system and left the ICV hooked up. That way I could have it idle without adjusting the throttle plate and throwing the tps sensor all to hell.
                          What do you mean by 'too clean'? I sprayed it with plenty of carb cleaner and lots of brown gunk came out.

                          Comment


                            #14
                            Yeah it utilizes some of the gunk as restriction to keep the parts from moving to freely. Let me see if I can find that wright up.
                            sigpic
                            85 swartz/metallic 325E
                            84 alpine 325E
                            85 zinnoberot 318i/R.I.P
                            84 Bronzit 318i/sold
                            purchase feed back here=http://www.r3vlimited.com/board/show...82#post3535282

                            Comment


                              #15
                              Oh, I think I see. Basically, the ICV becomes more sensitive, right? I would think that this would indicate an amplification of other issues and signify a properly functioning ICV...

                              Comment

                              Working...
                              X