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1986 Austin Montego EFi with cold start issues

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  • #16
    Fuel ECU wiring details
    Attached Files
    1958 Ford Consul Convertible. I love this car
    1965 Ford Zodiac Executive. Fab cruiser being restored
    1997 Jaguar Xk8 Convertible. Such a fab car
    2004 MGZT cdti. Great workhorse
    2004 MGZT V8. Black now with new engine and gearbox

    Comment


    • #17
      Thanks Jeff. Here's another update from the mechanic. Sounds like it could be the ECU?


      I have had some more time on the car, a bit at the end of last week and some today. What I did and what I found out:

      1. The cold start on Friday morning, whilst initially making me think it was better, once warm it seemed to be worse.
      2. I found the ballast resistor that is in the coil to ECU wire, removed it, cleaned the contacts, made sure it wasn’t
      open circuit, hooked it back up
      3. I refitted the black stepper this morning & fired the engine up with my stethoscope on the stepper:
      Ignition on - stepper operated
      Fire up, Initial idle was low (600RPM), slowly climbed 700, after about 2 minutes the stepper
      operated and idle dropped back to 600, after around 3 minutes more the revs were again
      around 700 and the stepper operated again dropping the idle to 650 (approx)
      Now warm I followed instructions to close stepper, disconnected it & tried to fire up but it
      wouldn’t until I’d screwed in the throttle stop screw - when running set base idle to 650,
      reconnected the stepper but it did nothing at all
      4. I found an article online about ECU issues with dry solder joints so I removed it, took it out of
      it’s case and examined it under a my magnifying lamp - no apparent dry joints or blown components

      I have these questions regarding the operation:

      1. When the stepper operates on ignition on how does it decide where to position the pintle? I am assuming this is just a basic setting unrelated to anything on the input as you can close the stepper by disconnecting it and reconnecting it with ignition turned on and off.
      2. Once the engine is running how does the ECU set the position of the stepper? The stepper only has an effect on the idle speed, I am guessing the main source of this would be the input from the coil, fine tuning would then be done using the inputs from the temperature sensor & air flow sensor. This detail information is hard to find so I can't confirm.

      In an ideal world I’d like to swap the ECU, I spent a bit of time looking and came up with this:

      https://www.johnrichardssurplus.co.u...u-auu1051.html

      The only issue with this is the part number, it’s listed as AUU1051, yours is AUU1051E, I have no way of finding out what the difference is.

      I will have time to talk this through tomorrow if you want to give me a call when you are free.

      Best regards,

      Chris

      Comment


      • #18
        Will, E means exchange on the part number. That ECU isn't available on his link
        You would be better buying these manuals to help Chris your mechanic as the bottom one covers everything for you car Chris is asking information on. It's available on Facebook selling pages. Just look up Austin montego
        I'm away ATM enjoying London but will look up what Chris has asked for on my return as I've forgotten and need to look it up
        Attached Files
        1958 Ford Consul Convertible. I love this car
        1965 Ford Zodiac Executive. Fab cruiser being restored
        1997 Jaguar Xk8 Convertible. Such a fab car
        2004 MGZT cdti. Great workhorse
        2004 MGZT V8. Black now with new engine and gearbox

        Comment


        • #19
          Cheers Jeff. I will see if I can find on FB. Any pointers appreciated

          Comment


          • #20
            The mechanic has now fitted a new ECU and seems to think he's got the car running as well as he can and said it drove well from cold today. Starts without throttle at about 850rpm and idles down to about 750-800rpm when hot. Says you can here the stepper motor now working, which you couldn't hear before. Sounds like he's had enough now, so guess I just have to go and collect it and see how it drives.

            Comment


            • #21
              Collected the car. Started OK from cold but needed a few seconds to fire. Sounded a little bit spluttery for a minute and idled about 850rpm. Drove well. When hot it probably idled about 750rpm. Stepper is doing something but not convinced its working properly and may even be the incorrect one as its like its not operating to its full range. I think I need to get with someone who's runs bang on and see if they will let me borrow their stepper to test

              Comment


              • #22
                Originally posted by Wild Bill View Post
                Collected the car. Started OK from cold but needed a few seconds to fire. Sounded a little bit spluttery for a minute and idled about 850rpm. Drove well. When hot it probably idled about 750rpm. Stepper is doing something but not convinced its working properly and may even be the incorrect one as its like its not operating to its full range. I think I need to get with someone who's runs bang on and see if they will let me borrow their stepper to test
                I'm a bit far behind due to work. holiday, working on my MGZT V8, diesel and Chris etc but seems you're about 90 percent there then. you could try changing it? https://www.ebay.co.uk/itm/321450124...2FHYT4HCVN6MZJ
                Last edited by Jeff Turbo; 31st August 2024, 12:04.
                1958 Ford Consul Convertible. I love this car
                1965 Ford Zodiac Executive. Fab cruiser being restored
                1997 Jaguar Xk8 Convertible. Such a fab car
                2004 MGZT cdti. Great workhorse
                2004 MGZT V8. Black now with new engine and gearbox

                Comment


                • #23
                  Cheers Jeff. I think I will look at getting one but want to be 100 it's the correct one. From experience, are there different types or all pretty much the same?

                  Comment


                  • #24
                    Decided to change the stepper again. Unfortunately no improvement. It appears that it doesn't do anything beyond initial instructions at ignition. I plugged the old one in and held it in a bottle whilst my Mrs to started the car. With ignition on the stepper pushed out. When starter engaged it moved very slightly outwards. With the engine running it didn't move, including when revved. Stepper contracted when engine switched off

                    Comment


                    • #25
                      As the car smells quite strongly of petrol when started, I am thinking the mixture screw isn't quite right. I am going to see if a local garage can test the CO2 and adjust to 2.5% and see if this improves things

                      Comment


                      • #26
                        You either have a leak or it's running very rich. On early cars there is a mixture adjustment screw but that was discontinued
                        1958 Ford Consul Convertible. I love this car
                        1965 Ford Zodiac Executive. Fab cruiser being restored
                        1997 Jaguar Xk8 Convertible. Such a fab car
                        2004 MGZT cdti. Great workhorse
                        2004 MGZT V8. Black now with new engine and gearbox

                        Comment


                        • #27

                          Comment


                          • #28
                            As I said, it was on early cars only and was discontinued in later models. You maybe lucky in that yours has the mixture screw
                            1958 Ford Consul Convertible. I love this car
                            1965 Ford Zodiac Executive. Fab cruiser being restored
                            1997 Jaguar Xk8 Convertible. Such a fab car
                            2004 MGZT cdti. Great workhorse
                            2004 MGZT V8. Black now with new engine and gearbox

                            Comment


                            • #29
                              I got an email from the mechanic today and he seems to think the speed sensor could be playing a part in the low idle:

                              Hi Will,


                              Sorry for taking so long to reply, have had a few things in the workshop to sort.

                              There is a chance that the mixture adjust is incorrect but I don’t think it is that which is causing the low idle. I do not have a CO analyser but my pal runs a garage with an MoT station, he sometimes will let me check and set this if I pay him for the time.

                              Today I called Roger Bywater at AJ6 Engineering, he’s written a book on fuel injection so the main reason for speaking to him was to buy this but it also allowed me to make a contact and start a discussion about the issue. One thing he mentioned, other than that he hadn’t done much with the Lucas system for many years, was that the vehicle speed sensor can cause idle problems if the ECU thinks the car is moving when it is not. I’ve downloaded the book this evening and will be reading through it over the next few days, I will see if anything comes to light that will point me in the right direction and be in touch after the weekend.

                              Best regards,

                              Comment

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