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  • lambda control issues

    my daily driver URS6 avant needed a clutch recently so i installed one. did not touch anything else in the car. car ran perfect before i took it apart. now since i put it back together the lambda control decides to either turn itself off or when it does become active it will stay around 14.7 for a short period than the requested AFR strays way off to like 25AFR and wont recover from it unless shut off and restart the car than the process starts over. when the requested AFR strays off the car is not drivable at all till shut off and restarted. never seen this problem before even and i've been fighting with it for 4 days now.

    for more detailed info my load is around 19-20 at idle with the engine at operating temp. injector constant is set to 632 at 3bar fuel pressure though i have 630cc injectors but close enough. when lambda control is shut off by setting that map to 0 requested AFR goes to 14.6-14.7AFR and car idles at 14.4-14.7AFR. no vacuum leaks in the intake as vacuum in reads perfect in the ECU and it was smoked tested. im using zeitronix ZT-3 wideband controller with the simulated 0-1V output for my lambda sensor. i tried disconnecting the wideband and putting an OEM bosch sensor in its place with the same end result. not sure what to do here and any input would help.
    "The really good drivers got the bugs on the side windows." Walter Röhrl

  • #2
    looked at the basic function of both basic lambda control and adaptive lambda control and as a test i disabled all access to read or write to TRADTV (RAM 61) along with flag byte 2A.1 in RAM and it seems doing that speeds up the drifting of the lambda and the lean condition almost instantly. normally it took it a while for it to happen. still not sure what is causing it to drift like this though. I also removed pin 28 on the ECU connector for the lambda wire and installed my own allowing me to tie the zeitronix controller directly into the ECU in case there was an issue with the stock shielded lambda wire. still didnt help.
    "The really good drivers got the bugs on the side windows." Walter Röhrl

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    • #3
      Check RAM_2 (lambda input) and then check your code what happens when - integrator resets etc. pp.

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      • #4
        Originally posted by Acki View Post
        Check RAM_2 (lambda input) and then check your code what happens when - integrator resets etc. pp.
        RAM_2 or X_RAM_2?

        not sure if this might indicate anything but in 2 out of my 3 cars the check engine light flickers when the high speed logging is running. the 2 cars with the flicker issue had VEMS on them previously. im starting to wonder if VEMS my have broke something grounding control related? also in the swapped car the tach not only reads till 1500RPM than drops dead but its lambda control works fine. tested the tach issue with a second known working cluster and it does the same thing. checked tach signal with oscilloscope and above 1500RPM there is still a noticeable pattern but it seems to have some sort of interference. not really worried about the tach not working, but just throwing that out there for reference, the lambda control is a real problem though.
        Last edited by vwnut8392; 10th July 2019, 19:39.
        "The really good drivers got the bugs on the side windows." Walter Röhrl

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        • #5
          Heres's a winlog file that i took that shows the problem. car is sitting there idling and the AFR just simply strays off as soon as the lambda control comes on.
          Attached Files
          "The really good drivers got the bugs on the side windows." Walter Röhrl

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          • #6
            There is something wrong in your settings or in code.
            On beginning even in hot engine 77C the AFR Req is straight line. Lambda control is on after 62 degree Celsius on ECT. This means that for some reason lambda control is not working correct or it's working, but code is wrong and calculation of AFR req is wrong. This if you checked lambda sensor signal and lambda controller.

            Then mixture quickly becomes lean - this mean that "AFR calculation" working i.e. calculates something, but input parameters is wrong or missing or some code is wrong also.

            on WOT AFR req going back to "normal" - this is a signal that values from lambda control for some reason are wrong. Even on "normal" you have big difference between AFR req and AFR actual. Bit this is different case.

            In WOT the "AFR calculation" resets the values for IPW to "stoich" 80 hex and add only values from AFR map and ECT/ IAT correction maps, without lambda calculation values.

            This is your direction where can be the problem.

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            • #7
              Lambda controller don't get the power from the lambda heater relay?

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              • #8
                Originally posted by Acki View Post
                Lambda controller don't get the power from the lambda heater relay?
                28/55- Input from G39 Heated Oxygen (O2) Sensor - G/G- This is the single black wire coming out of the O2 sensor to a single spade connector in the harness at the connector rack. The two white O2 wires are for the heater and are not run through the ECU.

                For lambda controller - it's should be on ECU main board showed on pic's in other topics or... the owner should tell
                Last edited by d_anev; 11th July 2019, 09:00.

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                • #9
                  thanks d_anev! i will look it over more. like i said in my initial post i changed the cars clutch and this problem developed. one thing that did show up is a 00525 fault which is short to + with the lambda controller but i find it strange because im using simulated wideband from zeitronix ZT-2. i hard wired the controller straight to the ECU removing the stock lambda wire and pinning my own right into the ECU connector. i also swapped the controllers with a brand new one right out of the box and i still got the same end result. its such a strange problem i have never encountered before.
                  "The really good drivers got the bugs on the side windows." Walter Röhrl

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                  • #10
                    Originally posted by vwnut8392 View Post
                    ....like i said in my initial post i changed the cars clutch and this problem developed. one thing that did show up is a 00525 fault which is short to + with the lambda controller but i find it strange because im using simulated wideband from zeitronix ZT-2..
                    Then here maybe is your problem.

                    A clamping or interruption of the lambda cable with the gearbox and the problem is present. You are not the first with that problem after swap of clutch.

                    Check the signals from the lambda probe to the controller i.e. the integrity of the lines and then the correctness of the signal. Then check if something has been burned on the controller as a result of a cable short circuit.


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                    • #11
                      Originally posted by d_anev View Post
                      The two white O2 wires are for the heater and are not run through the ECU.[/FONT]
                      Ok - at my V8 its controlled by the ECM

                      I had a short to + DTC and it's caused by the voltage DTC limit for the lambda signal. Standard is ~1.1V for lean and some wideband controllers send out a little bit more. I raised the limit to 1.2V, no DTC set again.

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                      • #12
                        Originally posted by Acki View Post
                        Ok - at my V8 its controlled by the ECM
                        I'm not sure about that. If your V8 is with M2.4.1 the lambda heater is powered by contact of relay J208 which is controlled by ECU.

                        DTC is only signal/direction that there is a problem with input signal from lambda sensor or controller in that case. You can adjust FR min/max values or 5 levels of lambda signal to avoid DTC, but in that case there is more complicated problem. The settings of lambda controller can be resets by short to + or clamping between wires. Even stock lambda sensor will send wrong signal if cable is clamped or short to +.


                        V8_ECU_Wiring.jpg

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                        • #13
                          Simulated output does not work right, it does not react like a normal narrowband sensor. There is more than just rich/lean switch in the ADC.
                          http://tuner.ee - http://www.facebook.com/tuner.ee

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                          • #14
                            @d_anev: I don't use the relais - I have installed a LC-1. But I know some guys use the relais and don't modify the table to have always power at the relais No "heater" function anymore.
                            During coast down I have sometimes rich mixture short before the fuel cut kicks in and this caused the DTC sometimes - I modified the DTC limit (VSRMX I think was it) a little bit and not DTC again.

                            Somewhere I had found the Bosch patent about the switch, it's a little bit more yes.

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                            • #15
                              well just to let you guys know that i found the root of the problem. the problem was a grounding issue with the strap that goes from the passenger side engine mount under the turbo to the frame rail. it had a lot of gunk and corrosion on it. removed it, cleaned everything and lightly sanded the contact surfaces and everything is good to go. so of the things i seen aside from the lambda control issue is my oil pressure gauge would not function properly, my coolant gauge would creep up higher than normal operating temperature but the logging displayed proper temp, also when headlights where on battery voltage on both the dash and the logger showed low 12v. that ground strap is obviously very important so if anyone has any similar problems in the future check that strap to make sure its clean and making good contact.
                              "The really good drivers got the bugs on the side windows." Walter Röhrl

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