Announcement

Collapse
No announcement yet.

If the black cover on the AFM goes missing...

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

  • If the black cover on the AFM goes missing...

    If the black cover on the AFM goes missing, will it affect the engine's running?

    Long story here, but the black cover on my AFM has been lost, and the car is running like crap. I have a theory that there's a vacuum leak through the AFM's body with the cap gone that's causing a lot of running issues, but there could be more to the story.

    Any ideas are greatly appreciated.

    (BTW: I'm definately on the market for a replacement cap!)

    - Mike
    The day ain't over yet....

  • #2
    Mike,

    I’m sure others will have some good suggestions, but I’d want to get the AFM covered quickly. I wouldn’t want to expose the wiper arm and the track to the environment of the engine bay any longer than I had to. I believe there is also a temperature sensor under the cap of the AFM. It shouldn’t be hard to make a quick cover while you look for a real replacement. Looking around my desk, I see CD jewel cases and old credit cards that one could cut, glue and temporarily attach to your AFM with some silicone.

    While I’ve never compared AFMs from different cars, I raced a Spec Miata that had a really similar looking AFM. I wonder if the caps are a close match?

    Good luck,
    Hank

    Comment


    • #3
      Originally posted by Hank Cohn View Post
      Mike,

      [FONT=Calibri][SIZE=3]Im sure others will have some good suggestions, but Id want to get the AFM covered quickly...
      Yep, thanks for the confirmation -- I've already done that. It's easy enough to temporarily cover the thing to give it some protection, but the running problem is still there. I did an extra-good job with the duct tape to try to seal it entirely and the engine actually ran better for a few seconds, but quickly lasped into its poor running state.

      I'm hoping the caps on Bosch AFM units are pretty much the same. Hopefully it won't be difficult to find a replacement without having to buy an entire AFM.
      The day ain't over yet....

      Comment


      • #4
        PM me I have one of those cover caps. They are glued pretty well from the factory but I believe it's to contain water from getting in, and not to prevent a vacuum leak. Although it may happen. I why is the cover missing? That little board is kinda sensitive specially after it gets tampered with.

        Comment


        • #5
          I don't believe there would be a vacuum leak problem, just a corrosion and grit problem. You could probably test it by taping off most of the surface and holding a cigarette near the unsealed area and seeing whether smoke is drawn into the cover as the engine idles.

          Comment


          • #6
            If your AFM cap has been removed for some time, then it does not surprise me that your car is running poorly. Under that cap is in effect a large potentiometer. The round dial carries voltage that completes a circuit when the AFM barndoor is in various positions. This in turn is the feedback to the Montronics to tell the car what spark and fuel maps to utilize.

            Without the cap, the circuit board is likely very dirty and the dial also. Go to radio shack, buy some electrical contact cleaner spray. Use a Q tip and carefully, gently clean all the electrical goodies under that cap. It may take a couple cleanings / applications. Also, be sure to check that the round dial's contact is making a uniform connection as it rotates across the circuit board. you may need to 'adjust' it slightly by subtly bending it. Let it sit out over night to dry/evaporate. Then seal it up with a new cap, air tight. Next, use some brake cleaner and carefully clean the airflow portion of the AFM, checking the barndoor for smooth operation and clean the air temp sensor carefully.

            Mark M
            Last edited by ///Empowered; 07-28-2008, 06:55 AM.
            E30 M3 / E46 M3 / E83 X3

            Comment


            • #7
              Originally posted by ///Empowered View Post
              If your AFM cap has been removed for some time, then it does not surprise me that your car is running poorly....
              That's all good advice, but the cap has only been gone a couple of days. It was "lost" at the shop where I'm having the car painted. Apparently the lummox who uses compressed air to blow loose stuff off the engine when they're through painting was unconscious as he blew off the engine. It appears that the cap lifted right off and flew away somewhere.

              I only noticed it was gone when I lifted the hood to check fuses (the windows wouldn't roll down, but that turned out to be a popped circuit breaker).

              Fabricating a temporary cover hasn't helped the running issue -- my concern is that the idiot also hurt the temp sensor or something else under the cap. What a jerk. The shop's owner said he'll make it right, but I don't believe he has any idea what a replacement AFM costs for these cars.
              The day ain't over yet....

              Comment


              • #8
                Not good. The dust cover is really important for the sensitive electronics. Also I believe it can be prone to air leaks in the system.
                Fully Restored 1985 Corolla GT-S
                1987 328ci SR20DET Drift Car (Will Convert to M3 Spec soon)
                1989 Honda Civic Si-R Current Project
                2002 Corolla CE Daily Driver

                www.TheTunerSource.com

                Comment


                • #9
                  Originally posted by F0Bman View Post
                  Not good. The dust cover is really important for the sensitive electronics. Also I believe it can be prone to air leaks in the system.
                  That's exactly my concern. The car runs as though there's an air leak in the system, and until I can get the cap replaced I can't be sure the running problem is because of the cap missing or some other issue.

                  I'm not a happy guy at the moment -- the car is painted and ready to go, but doesn't run well enough to take on the road. What a drag.


                  - - - - - - - - - - - - - - - - - - - - - - - - - AUTOMERGED! There's no thread "bumping" or "double posting" within a 24hr period. - - - - - - - - - - - - - - - - - - - - - - -


                  Update on this issue -- the paint shop was able to arrange a replacement cover for the AFM (brand-new Bosch part, from a Mercedes shop -- must be that Mercedes lists these as a replacement part).

                  My car is running perfectly with the new AFM cover on. There must be a really bad air leak, or something that keeps the AFM from properly signalling with the cover off.

                  Moral of the story is to take care of that dang thing. If, for any reason, you find it necessary to pop that lid, be sure to get it back on securely as soon as possible.

                  Thanks for all the input! Obviously it's not something to let go missing.
                  Last edited by ///mike; 07-29-2008, 03:20 AM. Reason: Automerged Doublepost
                  The day ain't over yet....

                  Comment


                  • #10
                    Originally posted by ///mike View Post
                    It was "lost" at the shop where I'm having the car painted. Apparently the lummox who uses compressed air to blow loose stuff off the engine when they're through painting was unconscious as he blew off the engine. It appears that the cap lifted right off and flew away somewhere.
                    Well, in that case, have that f*ker go and find it! Apart from that helpful word of advice: any other AFM cap will fit only the BOSCH number will be different which will make it look like you're running the wrong AFM. Get ready for questions at meets and once selling time comes :-)

                    Comment


                    • #11
                      Did you check around in the engine bay? When I bought my car I was missing the cover to the barometric sensor so I went and bought a new one. About a month later I was detailing the bay and ended up finding the cover wedged in stuck where I wasnt able to see it before. Look hard it might be in there!

                      Comment


                      • #12
                        Originally posted by hardtailer View Post
                        ...any other AFM cap will fit only the BOSCH number will be different which will make it look like you're running the wrong AFM. Get ready for questions at meets and once selling time comes :-)
                        Hadn't thought of that. The one the shop found for me is from a Mercedes. I bet the part number on it is not what you'd expect. The new cover also has "BOSCH" in big letters on the cap -- I don't recall that on the original. I believe the original was just plain without any logo.


                        - - - - - - - - - - - - - - - - - - - - - - - - - AUTOMERGED! There's no thread "bumping" or "double posting" within a 24hr period. - - - - - - - - - - - - - - - - - - - - - - -


                        Originally posted by 4bangr12 View Post
                        Did you check around in the engine bay? ...
                        Yep, did that as best I could in the bright (and really hot! down here in Florida) sun. I had hoped it just fell down in all that mess under the plenum, but no luck. It may be there yet, but I'm okay with the replacement the shop arranged.
                        Last edited by ///mike; 07-29-2008, 04:41 AM. Reason: Automerged Doublepost
                        The day ain't over yet....

                        Comment

                        Working...
                        X