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  • #76
    Originally posted by TekTac View Post
    Lago Blue has given some top notch suggestions and solutions for this lifelong problem. Amazing how into detail you are willing to go just to help a lost friend out. This thread is ready to be the "go-to" thread when 20v NA owners experience idle issues. lol

    I had a funny solution to my idle issues with my 2.0-20V NM motor (lil brother of 7A). I had bought the car with a bad cold idle and after exploring countless hours in the engine bay, replacing all kinds of stuff and READING a sh** ton of info about 7A motors I finally noticed something that wasn't supposed to be where it was.

    The PO had put a fuse on top of the fuel pump relay.

    explanation to the unaware... a fuse is placed on top of the relay ONLY when setting the idle speed and CO-value. It locks the timing to 14? degrees advance and probably something else i can't remember right away..

    The best part is i drove the car easily over 10 000km with the fuse in place and basically the car always in "idle setting mode". IIRC the symptoms were (1.) faulty idle most of the time (only not when engine was fully hot(of course, because the idle setting is supposed to be done with a warm engine)), and (2.) I think I felt the timing lock dissapearing and changing to normal upwards 2000rpm. The change was noticeable as the car was stuttering at around 2000rpm.

    But that's all.. do check that you don't have a fuse in there... on the fuel pump relay...
    Thanks for youre reaction, i checking the fuse and there was a fuse inside the relay. I remove it and test it again. The idle is now higher. But also fluctuated at warm engine.

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    • #77
      Your car will have fuel mixture and Idle speed values all over the place now - if you or a previous owner has been attempting to get it right with the fuse still in the relay - it will never be right!

      If you have eliminated vacuum leaks, crank case breather leaks, MAF function, injector problems, ISV problems and spark plug leads, coolant temperature sensor, lambda function then; there is nothing else for it but pay someone to set the idle mixture to 0.5 - 0.7% CO with the fuse in the relay then take it out and let the computer take over.

      With the fuse in the relay, your lambda probe is 'disconnected' so your computer isn't trying to trim the fuel while you are adjusting it. Once warm and driving in normal service, your lambda should always bring or at least try to bring the fuel air ratio to be 14.7:1. With it 'disconnected' the who knows what is going on??!!

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      • #78
        Hi TekTak,

        - You are too kind sir, certainly this could do with being about 5 pages shorter so that one could simply go to; rather than having to go through!

        - In all the years of seeing that NM engine designation in various catalogs, until today, I had no idea what it meant, fascinating:

        Check out this S2 forum link.

        That there are naturally aspirated 2.0 20v 5-pots out there raises some interesting questions (such as possible tuning ideas, comparison of various component specs and dimensions, possible parts-swapping and perhaps even ways to rev higher and burn less fuel) for another day. It also reinforces the need for - doing things to lighten the car.

        Hi Steve, Mike and TekTak,

        - Q: I had thought fuel-pump relays with those single fuse-holders on top (see photo) were just on the earlier CIS cars to pull codes and do that fixed idle thing; and on later 7A's to do the idle speed/CO. Are you guys saying they may have been installed at the factory on some early B3 20v's like what Mike's is now? My early 7A does not have the relay w/fuse holder (and I thought the proceeding was why), but I suppose it could have originally? Perhaps that a fuse installed thusly (as on Mike's car?) has some effect is evidence that such was the case?



        That the fuse's presence is for diagnostic purposes only and that this fuse-holder should otherwise remain empty (and that an unaware owner might just think it likely best needs a fuse installed) are good simple checks one could do, thanks for that.

        Meanwhile and back to the future with the still fluctuating idle, at this point I'm tempted to say, and perhaps some would agree; it may then be the flux capacitor (sorry couldn't resist!).

        Haynes DeLorean Wrkshp Manual.png

        But seriously, Mike, were you able to see if you could "move" the non-firing cylinder to another by switching two entire ignition leads (if length allows, label and remove them from the loom) around and/or perhaps eliminate the non-firing cylinder by replacing the old leads with new ones? Note this one lead end (your photo below) in foreground shows dirt and boot end damage (the ends harden then crumble with age, and with exposure to heat and oil), both of which could cause spark to bleed off (and possibly do so intermittently) before reaching the spark-plug.

        Mikes HT lead ends 2.png

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        • #79
          I've got a few relevant pages of the factory repair manual that covers the relay / fuse set up and both early and late ecus seem to have it...

          It is indeed for set up mode and putting the fuse onto the relay removes ecu control of mixture and idle (ISV) it sets the timing to a figure I forget, takes away lambda control of fuel which is the most important as mixture needed to Idle is very different to mixture needed for driving and assumes the coolant temp sensor is at 80deg c. All of those things are other wise involved in the running of the engine when no fuse is in the relay.

          I thought diagnostics was more to do with the plugs under the dashboard, led and counting flashes. That doesn't need the fuse installed to work (well at least on European models at least)
          ​​​​​​
          What I found to be causing the problem with my bouncing Idle was that the settings had been adjusted so much that the computer was always trying to compensate and bring either Idle or mixture back to what it is expecting. The bounce I put down to it just not being quick enough sometimes! The idle control at least is an electro mechanical device and physically moving a valve is never going to be as quick as modern ecu only control of Idle, roll into the mix either a tired or sticky / dirty ISV and the boincing Idle is the result.

          You HAVE to set the baselines to what the manual says so the computer and ISV have the least amount of work to do and stand the best chance of doing it!

          Analogy: Imagine adjusting the volume on your stereo to be 5 but you start at either 1 or 10 on the dial. That takes longer to do than if you started at 4 or 6 doesn't it? That's the theory behind setting baseline figures using proper kit. ​​​​​​​

          Comment


          • #80
            Originally posted by steve briance View Post
            I've got a few relevant pages of the factory repair manual that covers the relay / fuse set up and both early and late ecus seem to have it...

            It is indeed for set up mode and putting the fuse onto the relay removes ecu control of mixture and idle (ISV) it sets the timing to a figure I forget, takes away lambda control of fuel which is the most important as mixture needed to Idle is very different to mixture needed for driving and assumes the coolant temp sensor is at 80deg c. All of those things are other wise involved in the running of the engine when no fuse is in the relay.

            I thought diagnostics was more to do with the plugs under the dashboard, led and counting flashes. That doesn't need the fuse installed to work (well at least on European models at least)
            ​​​​​​
            What I found to be causing the problem with my bouncing Idle was that the settings had been adjusted so much that the computer was always trying to compensate and bring either Idle or mixture back to what it is expecting. The bounce I put down to it just not being quick enough sometimes! The idle control at least is an electro mechanical device and physically moving a valve is never going to be as quick as modern ecu only control of Idle, roll into the mix either a tired or sticky / dirty ISV and the boincing Idle is the result.

            You HAVE to set the baselines to what the manual says so the computer and ISV have the least amount of work to do and stand the best chance of doing it!

            Analogy: Imagine adjusting the volume on your stereo to be 5 but you start at either 1 or 10 on the dial. That takes longer to do than if you started at 4 or 6 doesn't it? That's the theory behind setting baseline figures using proper kit. ​​​​​​​
            thanks all for the good support and reactions, i read all of it and i thinks you are all right about the fuel mixture so high. but how can i put the mixture back at orginal settings. is there a way to get it back or does i need to drive and wait long time to i set back to normal? i hope that someone know how to set is back.

            Comment


            • #81
              Put fuse in fuel pump relay and turn the screw on the MAF! It will be under the round black plastic cap and IF it has never been adjusted, it will have a red tamper proof plastic cap over it.

              Adjusting mixture usually affects the idle speed and vice versa. You need to make small adjustments to each in turn as they affect each other.

              First thing to do of course is find someone with the CO gas tester and knows how to use it (unless you have your own) don't adjust anything until you know it is wrong!

              If you end up making adjustments, once finished take fuse out of relay and rev engine to 2500-3000rpm once and let it settle down. That quick rev takes it out of set up mode.

              As far as I know, the 7a ECU doesn't have a learning function so taking it for a drive won't help. I could be wrong of course but think self learning on such an early car is a myth.
              ​​​​


              ​​​​

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              • #82
                Not sure about mixture, but it does self learn the ISV current.

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                • #83
                  Originally posted by steve briance View Post
                  Put fuse in fuel pump relay and turn the screw on the MAF! It will be under the round black plastic cap and IF it has never been adjusted, it will have a red tamper proof plastic cap over it.

                  Adjusting mixture usually affects the idle speed and vice versa. You need to make small adjustments to each in turn as they affect each other.

                  First thing to do of course is find someone with the CO gas tester and knows how to use it (unless you have your own) don't adjust anything until you know it is wrong!

                  If you end up making adjustments, once finished take fuse out of relay and rev engine to 2500-3000rpm once and let it settle down. That quick rev takes it out of set up mode.

                  As far as I know, the 7a ECU doesn't have a learning function so taking it for a drive won't help. I could be wrong of course but think self learning on such an early car is a myth.
                  ​​​​


                  ​​​​
                  I have tried to change the MAF with the screw but no prehaps that red plastic cap was in it. I removed it and change it. But there is no difference. The Sparks wet. Or do I change it with engine not running ?

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                  • #84
                    The adjustments need to be done with the engine running so you know what effect it is having.

                    What figures did you see at the exhaust pipe when testing? Most cars of this era seem to have lost their catalytic convertor by now and in the UK at least; pre 1993 cars don't need one for the mot. If your country means the catalytic convertor has to be on the car - there is a exhaust gas sample pipe under the bonnet which comes off the exhaust manifold. This is PRE cat which means you can see what effect adjustment have without the cat' affecting emissions.

                    If your plugs are wet after running, that suggests quite a lot of excess fuel. I don't know if your engine management could be adjusted rich by that much.

                    Excuse me if you've already said so in this thread but, have you tested the injectors? The Hitachi units are all very old now and could quite easily not be closing off properly...
                    ​​​

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                    • #85
                      Originally posted by steve briance View Post
                      The adjustments need to be done with the engine running so you know what effect it is having.

                      What figures did you see at the exhaust pipe when testing? Most cars of this era seem to have lost their catalytic convertor by now and in the UK at least; pre 1993 cars don't need one for the mot. If your country means the catalytic convertor has to be on the car - there is a exhaust gas sample pipe under the bonnet which comes off the exhaust manifold. This is PRE cat which means you can see what effect adjustment have without the cat' affecting emissions.

                      If your plugs are wet after running, that suggests quite a lot of excess fuel. I don't know if your engine management could be adjusted rich by that much.

                      Excuse me if you've already said so in this thread but, have you tested the injectors? The Hitachi units are all very old now and could quite easily not be closing off properly...
                      ​​​
                      you set it while you running 2000 rpm or first at idle set and than to 2000 rpm ? How much does I turn it the screw? A little bit or 2 turns? What direction left for møre fuel or right ? When do I removing the fuse on the Relay

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                      • #86

                        Not sure about mixture, but it does self learn the ISV current.
                        Cheers.
                        turbo1

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