Is this theory correct?
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  1. #1
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    Default Is this theory correct?

    OK techinical gurus

    Here's one I want run by you . It relates to a slightly lean running condition that results in missing at idle and when revved, but not noticable under load.

    In modern engines, the ERG valve does not operate when an engine is cold, or at idle, but starts to operate (open) as engine temperature rises, admitting some exhaust gas back into the intake manifold to 'cool' the intake mixture. The ERG is controlled by the engine management system via a solenoid arrangement that 'clacks' away, combined with a vaccuum hose attached to the EGR.

    Now here's the issue. As the ERG opens the engine starts to 'lean miss', but also at idle.

    Now one could jump to the conclusion that the EGR is faulty, but the miss occurs at idle, when ERG is not open. if the EGR is disabled, the engine 'lean miss' is there still at idle, but stops as the engine is revved. This would mean the lean running condition is not there at engine speed; ie when ERG is disabled (ie running richer).

    With no obviouisly signs of a vaccum leak, I wonder if the CAT is slightly blocked, increasing exhaust back pressure and leading to more exhaust being forced through the ERG at a given engine speed, therefore leading to leaner running condition than it should be. Or could the oxygen sensor be responding with erractic readings leading to a lean running condition if a CAT is slightly blocked.

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    This assumes all ignition components, injectors not blocked, and no fault coses registered, including oxygen sensor.

    In essence, a slight surge and stabble at idle, and at engine speed. But when the EGR is disables, it runs bloody great when revved.

    Hope you are not affended as this relates to my german vehcle and not the french machine.

    What you you think?

    Thanks,

    Scott

  2. #2
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    Anybody?? Need to explore all options for a lean running condition.
    Thanks Scott

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    Hi Scott,

    What injection system are we talking about? EGR is generally not used on later engine management as emissions are finely enough controlled by the system plus a three way cat. so I guess it's a late 80's or first half of 90's car?

    I might be able to give you some guidance if I knew which version of, I assume Bosch, injection it is.

    Stuey


    2003 PEUGEOT 206 GTi

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    Quote Originally Posted by Stuey
    Hi Scott,

    What injection system are we talking about? EGR is generally not used on later engine management as emissions are finely enough controlled by the system plus a three way cat. so I guess it's a late 80's or first half of 90's car?

    I might be able to give you some guidance if I knew which version of, I assume Bosch, injection it is.

    Stuey
    Stuey.
    Intially I though the VW caravelle had Bosch Montronic.

    But perusing further it has a Siemens SIMOS fuel injection Management system. It's a 2000 model with 2.5 5 cylinder petrol (audi motor). Definately has an ERG on top of the engine, that opens as stated. It has the usual MAF sensor, various ECU temperature sensors, oxygen sensor, knock sensor etc etc.

    It appears to be a lean running condition. No faults codes were detected. I am not sure though that would rule out vaccum leaks.....but nothing so far detected. Unlikely to be a blocked injector for a 60K engine...(but then I have stated such presumptious things before!!!

    Many thanks,

    Scott

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    Gee, Scott, that is weird, for two reasons. I thought VW would have had either Bosch or VW Digijet/Digifant, which around 2000 is essentialy the same as the contemporaneous Motronic.

    I can't think of anything - I'll consult my engine management bible.

    Stuey
    Last edited by Stuey; 17th September 2005 at 10:29 AM.


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  6. #6
    1000+ Posts Wildebeest's Avatar
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    Default Theory ?

    Quote Originally Posted by Stuey
    Gee, Scott, that is weird, for two reasons. I thought VW would have had either Bosch or VW Digijet/Digifant, which around 2000 is essentialy the same as the contemporaneous Motronic.

    I can't think of anything - I'll consult my engine management bible.

    Stuey
    Scott, Stuey,
    If the system has an EGR set up, [as we know it Jim] could the plumbing from the exh manifold have a hole burnt through it? This would in effect be a vacuum leak when the valve is open.

    Have the injectors been cleaned, tested and refitted with new seals?

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    Scott, I've been thinking too...wouldn't you get better advice on VW Vortex rather than is having a stab at what might be the case?


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    Stuey and Wildbeast,

    Thanks for your replies.

    No Vacuum leaks or ERG pipe leak detected.

    I will now head down the path of fuel pressure, MAF sensor tests. It is difficult when no fault codes are detected. Even a dodgy MAF sensor doesn't always throw a fault code.

    I also learnt that many late model AUDI and VW's have SIMOS engine management. Presumably this supersedes VW Digijet/Digifant and Bosch in some cases. I am sure there is not a lot of difference in the overall inputs.

    In terms of VW Vortex, I do look at the US and AUS sites.....not much in the way detailed techinical discussion!!!............. In fact, a lot of diatribe.

    Really just trying to establish as techincal theory.

    Much Appreciated.

    Regards,

    Scott

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    Stuey and Wildbeast,

    Thanks for your replies.

    No Vacuum leaks or ERG pipe leak detected.

    I will now head down the path of fuel pressure, MAF sensor tests. It is difficult when no fault codes are detected. Even a dodgy MAF sensor doesn't always throw a fault code.

    I also learnt that many late model AUDI and VW's have SIMOS engine management. Presumably this supersedes VW Digijet/Digifant and Bosch in some cases. I am sure there is not a lot of difference in the overall inputs.

    In terms of VW Vortex, I do look at the US and AUS sites.....not much in the way detailed techinical discussion!!!............. In fact, a lot of diatribe.

    Really just trying to establish a techincal theory.

    Much Appreciated.

    Regards,

    Scott

  10. #10
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    Default erg egr fault?

    If a fault exist with egr or erg my first thought would be to disconnect both. Reset the engine management system. Then attempt to determine which is damaged. The reason i suggest resetting is so there is nothing the computer has learned of the engine.

    The computer often will compensate if one item is stuffed.

    Otherwise rip both devices out and check there function on the bench.

    Als

  11. #11
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    Quote Originally Posted by AlsPug504
    If a fault exist with egr or erg my first thought would be to disconnect both. Reset the engine management system. Then attempt to determine which is damaged. The reason i suggest resetting is so there is nothing the computer has learned of the engine.

    The computer often will compensate if one item is stuffed.

    Otherwise rip both devices out and check there function on the bench.

    Als
    Alan, thanks for info. I have already reset. I don't think there is a problem with the EGR as such. But by isolating (disconnecting the EGR) it caused the car to run fine (in effect a little richer running) accept at idle....but no vaccuum leaks found. MAF sensor might be next attack/and or fuel pressure checks. But I will reset again just to be sure.

    All ignition components have checked out fine, the CAT is not blocked. Intially though it might have partially been blocked.

    Bloody difficult to isolate with no faults codes detected.

    I know this is not a french car, but might serve as general technical interest in any case.

    ERG??? Are you referring to the EGR relay? It works fine.

    Regards,

    Scott

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