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  • Hi Marc,
    If it was me I would solder a small jump wire between the damage circuit gap, since the ohm readings are within spec no need to replace the ICV, if the ohm reading are good from the ecu plug to the ICV I see no reason to install a fuse.
    After you have replaced the transistors a key on buzz check and then see if the idle is behaving as it should. Everything you have listed seems logical and in correct order for setting the base tuning.
    Finding someone with a CO meter is not so easy so I would not worry about that if one is not available where you live.

    E30 M3 1987
    Mini Clubman GT
    BMW E36 323 Msport
    Toyota Corona
    KTM 200EXC
    Honda CB50 (1979)

    Comment


    • Hi Dave,
      thanks for the quick feedback. The idea of the fuse was to avoid damage to the ECU if someday the ICV should fail. Does this make sense?

      Are you saying that the fuel mixture setting is good enough when I set it to 0,5V on the O2 sensor? Do I understand correctly that the AFM adjustment screw only adjusts the idle fuel mixture and not the fuel mixture at part or full throttle?

      thanks
      Marc

      Comment


      • Hi Marc,
        For piece of mind a fuse mounted somewhere near the ECU may well be good idea like you say incase of wiring/ICV future failure.
        Yes .5v close enough unless someone else has other thoughts/experience on the subject.
        My understanding is any fuel mixture above idle is set within the eprom programming and only idle mixture is adjustable when the idle switch wires bridged.
        I think the only exception would be the ignition/fuel calibration position switch inside of the ECU

        E30 M3 1987
        Mini Clubman GT
        BMW E36 323 Msport
        Toyota Corona
        KTM 200EXC
        Honda CB50 (1979)

        Comment


        • Thanks for your help Dave. As soon as I have the parts I will repair this and send some photos of the result.

          Comment


          • I read some more about the idle fuel mixture adjustment and basically found two different methods:

            - testing in open loop: disconnect the O2 sensor, connect the voltmeter to the signal contact of the O2 sensor, and adjust the AFM bypass screw until the voltmeter shows 0.4-0.5 V. I have seen this procedure described in several threads, for example here in one of Dave’s posts: https://s14net.vbulletin.net/forum/s...080#post737080

            - another approach for testing in closed loop is described here: https://s14net.vbulletin.net/forum/s...24#post1125324
            In this procedure, the O2 sensor remains connected and you measure the voltage between pin 5 on the diagnostic connector (which comes from pin 12 on the ECU) and ground while adjusting the AFM bypass screw. With an averaging multimeter the target average voltage is 6V, or alternatively a cycling of the voltage between 0 and 12V on an analogue multimeter with 50% duty cycle.
            A similar procedure is also described in this factory documentation (unfortunately only German): https://www.s14motorsport.de/0007/0007.htm
            in chapter 2.3 they describe the AFM adjustment by connecting a ‘"Lambdaintegratorgerät’" (Lambda Integrator Device) to the diagnostic port and to adjust the AFM bypass screw until you reach a regular blinking of an LED on this device.

            Is one of the two above described methods preferrable over the other, or are they completely equivalent?

            Thank you

            Comment


            • The open loop method works. The problem with the closed loop is that the S14 in the M3 does not have pin 5 wired to the Diagnostic Connector.

              Comment


              • That‘s interesting. Are you sure that it is valid until the end of the manufacturing period? The 1990 Electrical Troubleshooting Manual shows pin 12 of the ECU wired to pin 5 of the diagnostic port. I can check this tonight on my car.

                Even if it should not be wired to the diagnostic connector, would the method still work by using port 12 of the ECU? I think it would be interesting to validate that the engine is actually working in closed loop.

                Comment


                • I just checked the E30 M3 Electric troubleshooting manual from 1987 and also there the connection to the diagnostic port is shown: http://bimmertips.com/wp-content/upl...4/e30m3_87.pdf (Page 1364-0)
                  maybe it‘s a mistake in the document.

                  Comment


                  • On my car, pin 12 of the ECU is wired to pin 5 of the diagnostic port according to the schematics. Did anybody ever try out this closed loop method on this contact?
                    As soon as I’ll have the ECU repaired, I will try both methods for the setting of the idle mixture, and will report if both are equivalent.

                    Comment


                    • Interesting, the 1990 electrical manual does not show a pin 5 but the schematic on 1364-6 shows it wired to pin 5. Looking forward to your test.
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                      • I have checked today my 87 Euro spec has a terminal in the #5 position.
                        0v with key off, battery voltage in on and run positions using digital meter so not sure what that means.

                        E30 M3 1987
                        Mini Clubman GT
                        BMW E36 323 Msport
                        Toyota Corona
                        KTM 200EXC
                        Honda CB50 (1979)

                        Comment


                        • @jwbavalon: this must be a mistake in the BMW documentationthen. In the 1987 manual, the same „connector view“, page 8500-0, shows pin 5 as a „white/green“ wire, described as „motronic control unit“

                          @Dave: thanks for taking the time to test this. If I understand this signal output of the ECU correctly, it can have the following conditions:
                          • Stuck at 12V (or 0V?), which means that the ECU is operating in open loop for some reason.
                          • Oscillating between 0V and 12V. The oscillation shows that the ECU is running in closed loop. If this oscillation is perfectly regular between 0V and 12V, with a 50% duty cycle, then this means that the mixture is correctly set. If the oscillating signal does not have 50% duty cycle, but stays longer on the 12V side than on the 0V side, or vice-versa, this means that you’re either on the rich or on the lean side.
                          However, if I understand the requirements for measuring equipment to perform this test correctly, then this test cannot be done with a normal digital voltmeter. You either need an analogue voltmeter, on which you can physically see the needle oscillating and set the AFM bypass screw so that you have a regular oscillation by “visual judgement” (which should be close enough to 50% duty cycle), or you can use a digital voltmeter with averaging function, which calculates an average voltage when an oscillating signal is present. For a signal oscillating between 0V and 12V with a 50% duty cycle, these meters would show an average of 6V. If the duty cycle is slightly off, it would show e.g. 5V or 7V. According to the link posted above, the tolerance range for this signal is 5-7V.

                          I don’t know what happens when you measure the signal with a normal digital multimeter. I imagine that due to the oscillation, the display digits would simply change all the time, not allowing to make any sense of the reading. I cannot imagine that the oscillation is so fast, that the normal voltmeter would simply be stuck on either 12V or 0v, but I could be wrong.

                          Dave, was your engine cold when you measured the signal, or was it at operating temperature? In case it was still cold, I could imagine that you got the 12V reading because the closed loop control was not active on the cold engine? But this is just an assumption.

                          The description above is just the understanding I gathered from reading up on this topic. I’m not an electrician and it would be great if someone more knowledgeable in this topic would confirm or complete/correct the information above.

                          I will in any case perform both tests and compare the results and post it here.


                          Comment


                          • Okay I seen my error yesterday I had the oxygen sensor disconnected when I measured what was happening at pin 5. My engine was hot both days.
                            With everything connected up my cheap digital V meter reads at idle, 13.00 volts then it changes fluctuates down to as low as approx 2v then 7v and so forth if the revs are lifted it fluctuates quicker so something going on unfortunately beyond my measuring ability.

                            What we need is someone to make a diagnostic box which connects to the 101 and and has all the various test buttons and lights to suit all models of E30 series, it would be interesting to see what the service departments used when the M3 was new.

                            E30 M3 1987
                            Mini Clubman GT
                            BMW E36 323 Msport
                            Toyota Corona
                            KTM 200EXC
                            Honda CB50 (1979)

                            Comment


                            • That’s great news, I think that shows that the signal described in the closed loop procedure is actually there.

                              When I do my adjustments, I will try to get a hold of an oscilliscope, so that we get a better understanding of what that signal looks like and how it reacts to AFM adjustments. Also we will see how the 0.45V on the disconnected O2 sensor correlates with the 50% duty cycle / 6V average on the diagnostic port.

                              This document https://www.s14motorsport.de/0007/0007_03.htm references the tool that BMW used at the time, called Gemischkontrolladapter (Mixture verification adapter), part reference 130183. Unfortunately google doesn’t seem to know this tool.

                              Comment


                              • Hi Marc,
                                I have not checked previous posts regarding your rebuild but I presume you've at least honed your block and fitted new piston rings if not gone oversized pistons. As such I would break in the engine via the routine as outlined on http://mototuneusa.com/break_in_secrets.htm (or any other routine you're convinced of) and not run the engine without load or idling to check out the mixture.
                                You'll waste the window of opportunity to break in the engine properly IMHO.

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