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Idling problem on Corsa B. 1.2 16v automatic.

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  • [Corsa B 1993-2000] Idling problem on Corsa B. 1.2 16v automatic.


  • #2
    Welcome to the Forum.

    With cases like this, I find that it always pays to start with the basics. For example, is it anything like due for a FULL service? - If so, that MIGHT be enough to overcome the problem.
    It is also worth buying a can of 'Carb Cleaner' (Halfords) and use that, together with a small brush (old toothbrush?) to give the throttle body a good clean.
    You could also do worse than check for clean and tight electrical connections, particularly earth connections which may have corroded.

    Regards

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    • #3
      Firstly - to agree with the above, start with the basics.

      It's also worth asking if it does this from cold or does it happen more when it's warmed up? The reason being that a failing coolant temperature sensor (CTS) will give you exactly these symptoms. At idle the engine is running too rich so you get a lumpy idle and then eventually it cuts out. It will also make it hard to start when warm unless you floor the throttle.

      If you've ever driven an older car with a failed automatic choke (they usually fail in the on position) you'll know the symptoms.

      The ECU sets the fuel mix for a cold engine by default, as the engine warms up the CTS tells the ECU so the fuel mix is leaned out. A failing CTS will often not throw a fault code, the only sign you get is trouble on idle and starting problems. Since it is throwing the fuel mix out that can also show up as a Lambda problem, with many (so called) mechanics forgetting that since the Lambda is a feedback system most Lambda 'faults' are really just an indication of a problem elsewhere.

      They are cheap and you can fit one from any factors. The CTS is bolted into the top of the water pump so it's a simple thing to replace.

      Other thoughts - make sure the AFM they fitted is a genuine Bosch one, cheap ones are very unreliable. If you've got the original keep hold of it as it sounds like there's nothing wrong with it. (Any suspected issue with an AFM - just unplug it to force the engine into a default mode - no need to buy a new one to check.)

      The other common issue with these engines is the EGR valve, it that sticks it can cause starting and idle problems, also misfires, just depends how it's stuck. The thing to do there is to blank it off rather than replace it.

      If you want to clean throttle bodies the best thing I have ever found is a brew made for powerboat engines - QuickSilver Powertune. From a chandlers or ebay. It will clean things carb cleaner won't touch.
      1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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      • #4
        Corsa B idling problem.years

        Thank you Walksall and Taurus for your prompt and Kind replies. The car is now in my own garage but I had to have it transported from the local garage.
        The car is regularly serviced although I notice that the inside of the throttle body has some carbon deposits .I intend today to get some carb cleaner and scrub this off.The earth connection are good -I replaced the ECU myself and made sure that the seperate earh lead was replaced and then checked it with a test lamp to the battery.The observation about the temp sensor is interesting and I inend to replace this forthwith.
        I have heard that there is an idle adjustment screw beiow the throttle body but one needs to remove the 4.torqx setscews and lift up the body an inch or so to gain access to this screw.However I will do the cleaning bit and replace the temp sensor before I try this.
        It may be worth stating that the original problem and the reason it went into the garage for diagnosis was not an idling problem but rather a sudden loss of power when at some speed on the road accompanied by the "fault " light coming on. Clearly this was very dangerous if one was overtaking.The idle or starting was never a problem since this has only occurred since the local garage have attempted repairs. Now I am unable to find out if this original problem has now been fixed consequent on all the replacement parts since I cannot get the car on the road due to the idling cutout problem.

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        • #5
          Do you know what code the original fault was showing? It sounds like they have mucked something up trying to repair the original problem.
          1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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          • #6

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            • #7
              Just wondering if the new Lambda sensor was a genuine one - I've been led astray in the past by, "Oh, it's just had a new sensor fitted!" sort of comment. Some of these spurious aftermarket ones work OK (for a time at least) - Most don't!

              Regards

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              • #8

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                • #9
                  Reporting back after fitting yet another part namely the temp.sensor. Result no change -engine starts and idles erratically and roughly for a short while, sometimes maybe a few minutes, then revs drop to about 400 rpm and engine stops. The car can be revved above 1500 rpm right up to Max without a flat spot but when dropped to idle it again runs roughly and finally stops. So to recap : parts fitted: ECU, air mass meter,lamda sensor,throttle idle solonoid, temp sensor. Tried leaving battery earth lead off overnight,including turning on the ign.for 20.secs then off and repeating 5. times. All of the above with absolutely no effect on the idle problem. It is,of course,not really possible nor safe, to take the car out for a run. Any further suggestions would be gratefully received --I don't want to give up at this stage having spent more than I should have and I,m really loathe to scrap my wife's pride and joy!
                  Last edited by cambox; 24-10-2015, 12:06 AM.

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                  • #10
                    I never like guessing at answers to problems .....but -
                    The original problem sounds to me very much like a problem with the Hall sender in the distributor, when these are on their way out, the engine tends to just cuts out and won't re-start - leave it for a short while and it's OK again.
                    By the time you get round to actually checking for a spark etc, the thing is back to normal, so you don't find a problem at all - 'till the next time!
                    The Hall sender unit can be replaced, but it is a bit 'fiddly' and most people fit a new distributor.

                    Is there any chance that the garage who had the car may have disturbed a vacuum connection (to the brake servo, for example) air getting into the inlet manifold below the throttle body will cause idling problems.

                    Regards

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                    • #11
                      The Hall type dizzy was only fitted to the 8v engines up to 1996, the 16valve dohc engine doesn't use that system.

                      Disconnecting the battery won't clear the ECU, in theory it should ignore old codes but they don't always do that. Next thing to check is the egr valve, if that's stuck it can cause problems. Do check the vacuum pipes as suggested.

                      Check the state of the plugs to see if one is oiled up or showing signs of not firing right. It's worth checking the compressions just to make sure there's no mechanical issue.
                      1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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                      • #12
                        Hi Walsall. Thank you for your continuing helpful insights.
                        Regarding the EGR : when you say "blank it off--" do you mean disconnect it ? alternatively how does one blank it off?
                        Concerning the original problem the engine did not cut out completely rather it was a sudden marked loss of power and therefore speed particularly when the engine was working hard such as diving uphill .This was accompanied by the engine fault light ; the power would return for a time and then fall again ---this clearly was dangerous in traffic.
                        Regarding the vacuum connection these I will carefully check tomorrow .
                        Thank you again. Kind Regards. Mike.

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                        • #13
                          Hi. Taurus. Thank you for your kind reply and helpful suggestions. The EGR valve is now to be next on my list -- do I just disconnect it?
                          Best Regards. Mike.

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                          • #14
                            Originally posted by cambox View Post
                            Hi. Taurus. Thank you for your kind reply and helpful suggestions. The EGR valve is now to be next on my list -- do I just disconnect it?
                            Best Regards. Mike.
                            Sorry - been away and then my laptop died. You can just disconnect the EGR (it will show a fault code of course) but unless you know it is able to return to the closed position that may not help. If it is stuck open then disconnecting it won't help. To blank it off you need to remove it and fit a new blanking gasket between the EGR and the cylinder head. It's the same as the usual gasket but with part of the port area closed off.
                            1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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                            • #15
                              Thank you Taurus for your kind reply.

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