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Anyone tuning afm?

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    #1

    Anyone tuning afm?

    Ive been having idle problems lately and there has been no fix, so ive found a few adjustments to compensate for it. Now im trying to tune the afm to get maximum efficiency out of my old motor. To take care of the idle problem I (supposedly) leaned the idle mixture by using the hex screw adjustment on the outside of the afm. That has fixed my idle a bit.

    the other adjustments regarding the fuel mixture (spring dial) and the 'sweeper' have been giving me some trouble. For the longest time I was running to rich, based on the mpg gage, and the extra power the car had. I estimate about 22-24mpg when i normally get around 27-28. What can I do to get my fuel mixture set stoich and retain my current lack of power? I should be able to read outputs with a voltmeter correct? If anyone out there can give me some clues I'd appreciate it. I will be investing in a bosch injection book in the future.
    Old and improved:
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    #2
    Instead of adjusting the AFM, you need to find out why you are running rich.
    Causes:
    Vacuum leak
    Bad coolant tenperature sensor or wiring
    Bad fuel pressure regulator
    Leaky injector(s)...verify by inspecting spark plugs.
    Bad O2 sensor.
    John
    88 ///M3 Cinnabar
    84 318i Black

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      #3
      My idle problems started when my intake manifold gasket blew and i had a distinct vacuum leak. I removed the intake and put new gaskets on, reinstalled everything and my idle still wasnt fixed. The ICV is adjusted all the way in and before it would idle fine at 750, after it was around 1300. I know my o2 sensor is bad. When it is plugged in the idle surges up and down but the rest of the car runs okay. When its unplugged it will idle around 1100 and not surge.

      I have heard that a new o2 sensor can make a world of difference, and I think its time to bite the bullet and get one. I dont think its ever been replaced in my car because it is usually unhooked. The only thing that I have yet to check are the coolant sensors. Other than that everything checks out okay, and the kicker is that my plugs all burn fine. There is no sign of carbon or oil. I am going to try and set the afm back to stock settings and get myself a new o2 sensor.
      Old and improved:

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        #4
        If your idle problem occurs when the engine is cold, then a new O2 sensor won't help
        Originally posted by Jarvis
        Originally posted by Brew
        Guys, the O2 sensor doesn't function until the car is warmed up.
        :idea:
        True story. We were talking about it earlier and found this:
        "The signal from the oxygen sensor is ignored by the fuel injection control unit until the engine reaches a specified temperature. Therefore, when troubleshooting cold engine driveability problems, the oxygen sensor can be ruled out as a possible cause." - Bentley manual 3:8
        Also, do you have a spare ECU or is there anyone in your area that you can borrow one from? Last year in my old 325is I had a problem with it idling very low and stalling. A new ECU fixed that.

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          #5
          You know, that is the best news i have had all day. I dont have an idle problem when the car is cold. runs perfect when cold. its only bad when at normal operating temperature.

          Normally i dont run the sensor at all, but when it gets cold out (say under 45 degrees) i really had a problem with high idle, so i plug in the sensor and the idle goes to normal. Now its not doing that, so I am going to speculate that my o2 sensor is crap. If I cant get my afm back to normal i will just buy another used one and get the o2 sensor. I think thats my plan of attack.
          Old and improved:

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            #6
            buy an AFR meter or a Pyrometer an get some readings, cause if your running rich, your plugs will show.

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              #7
              I checked the price on a new e30 O2 sensor, damn near shit myself...a 3 wire Bosch sensor is HOW MUCH? Not like Bosch says, "OK guys, we need to recalibrate our productiuon line to make these sensors, so shut down while we make some changes" it is the same sensor with a different harness. I used to buy generic sensors, no one seems to have them anymore. Not enough profit, I guess.
              I bought a sensor from a Ford F150, like a '98 or so, was same number stamped on the body of the sensor. I soldered the BMW harness on, and carefully shrinktubed it. Was like $45 or so, vs $130 for "BMW part". All good for several months and more than 10K miles.
              HTH,
              Luke

              Closing SOON!
              "LAST CHANCE FOR G.A.S." DEAL IS ON NOW

              Luke AT germanaudiospecialties DOT com or text 425-761-6450, or for quickest answers, call me at the shop 360-669-0398

              Thanks for 10 years of fun!

              Comment

                #8
                Originally posted by StereoInstaller1
                I checked the price on a new e30 O2 sensor, damn near shit myself...a 3 wire Bosch sensor is HOW MUCH? Not like Bosch says, "OK guys, we need to recalibrate our productiuon line to make these sensors, so shut down while we make some changes" it is the same sensor with a different harness. I used to buy generic sensors, no one seems to have them anymore. Not enough profit, I guess.
                I bought a sensor from a Ford F150, like a '98 or so, was same number stamped on the body of the sensor. I soldered the BMW harness on, and carefully shrinktubed it. Was like $45 or so, vs $130 for "BMW part". All good for several months and more than 10K miles.
                HTH,
                Luke
                no kidding, i just bought one for a fraction of the price from someone off the board. Im pretty sure this problem will finally be coming to an end.
                Old and improved:

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