306 erratic idling
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  1. #1
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    Default 306 erratic idling

    Bought a 2 litre 306 ST recently and it has a very erratic idling problem, cold or hot. So far I've tried replacing plugs and the air filter, which hasn't changed the problem. The problem can occur at any time but not every time. For example, arrive at the traffic lights, and the engine speed will start to drop, and unless one keeps the revs up, it'll stall. Same thing sometimes on start up from cold.

    It's done 206,000 km. I dont know whether the oxy sensor is the original one or not, or whether this will make any difference at all to the problem. Fuel economy is about the same as the 1.8 litre 306s in the family, so I guess it's not running rich. Power is fine - it certainly goes much better than the 1-8 litre cars.

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  2. #2
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by pugnut1 View Post
    I dont know whether the oxy sensor is the original one or not, or whether this will make any difference at all to the problem. Fuel economy is about the same as the 1.8 litre 306s in the family, so I guess it's not running rich. Power is fine - it certainly goes much better than the 1-8 litre cars.
    I dont think that matters much.
    YOur o2 sensor needs time to warm up from a cold start, so its reading should not be part of the parameters the ecu uses for cold start idle.
    I'd start by inspecting and cleaning/lubing the idle valve.
    If that was sticking, it could cause erratic idle with no other signs.

    Everything else like temp sensor, fuel pump block injectors, intermittent TDC sensor, busted map sensor would show up at other times, not just idle, so I'd start with the idle valve and see what happens.

    Jo
    Last edited by jo proffi; 16th January 2011 at 03:03 PM.

  3. #3
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by pugnut1 View Post
    Bought a 2 litre 306 ST recently and it has a very erratic idling problem, cold or hot. So far I've tried replacing plugs and the air filter, which hasn't changed the problem. The problem can occur at any time but not every time. For example, arrive at the traffic lights, and the engine speed will start to drop, and unless one keeps the revs up, it'll stall. Same thing sometimes on start up from cold.

    It's done 206,000 km. I dont know whether the oxy sensor is the original one or not, or whether this will make any difference at all to the problem. Fuel economy is about the same as the 1.8 litre 306s in the family, so I guess it's not running rich. Power is fine - it certainly goes much better than the 1-8 litre cars.
    I'd suggest the idler stepper motor may be sticky and dirty and tired. It may respond to pulling off and lots of cleaning but perhaps just replace ($200 or so I think).

    This is not an uncommon issue on older examples of various Peugeot/Citroen and quite a few other brands too no doubt.

    "Bought a ... recently" suggests pre-existing issue. Warranty? I guess maybe private sale, in which case no come back.

    Good luck.
    JohnW

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  4. #4
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    Quote Originally Posted by JohnW View Post
    I'd suggest the idler stepper motor may be sticky and dirty and tired. It may respond to pulling off and lots of cleaning but perhaps just replace ($200 or so I think).

    This is not an uncommon issue on older examples of various Peugeot/Citroen and quite a few other brands too no doubt.

    "Bought a ... recently" suggests pre-existing issue. Warranty? I guess maybe private sale, in which case no come back.

    Good luck.
    Well, I paid $500 for it at the auctions (still registered). Good tyres, and everything was still there, with both bumpers already taken off and lying in the cabin. $800.00 for body repairs and it's back on the road. So this problem is not considered a big cost to fix it.

    I think cleaning is the first try.
    1998 Peugeot 406 D8SV Manual
    1999 Peugeot 406 D8ST Auto
    2002 Peugeot 406 D9SV Manual
    1994 Peuegot 306 N3 Cabriolet Manual
    1994 Peugeot 306 XR N3 Hatch
    1995 Peugeot 505 GTI executive
    1976 Peugeot 504 Sedan - Now sold

    Over 60 Pugs in my time
    Gerry Mullock

  5. #5
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by pugnut1 View Post
    Well, I paid $500 for it at the auctions (still registered). Good tyres, and everything was still there, with both bumpers already taken off and lying in the cabin. $800.00 for body repairs and it's back on the road. So this problem is not considered a big cost to fix it.

    I think cleaning is the first try.
    Oh well done!!!!

    Yes, cleaning.

    Cheers
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  6. #6
    1000+ Posts jo proffi's Avatar
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    The problem can occur at any time but not every time.
    Dwelling on the randomness for a moment, I had a thought, which may be well of the mark as I dont know the 306 efi system specifically.

    IS there any chance the idle solenoid only kicks in when the Throtle Position Switch(TPS) tells the ECU that the throttle is fully closed, and that the TPS is out of adjustment somehow and not quite closing ???


    IF something like crud was causing the throttle to not close as far as fully closed but not letting air in either, a quick way to maybe bully it closed would be to slam it shut, by pressing the throttle full way and slipping of it allowing it to spring back with as much force as possible.
    It is worth a try in absence of any diagnostic computer to plug into and it'll give you something to do while you are revving.
    The great thing about the diagnostics is these things often go bling in front of you and you dont have to mess about with things that aint broke yet.
    Jo

  7. #7
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    Quote Originally Posted by jo proffi View Post
    Dwelling on the randomness for a moment, I had a thought, which may be well of the mark as I dont know the 306 efi system specifically.

    IS there any chance the idle solenoid only kicks in when the Throtle Position Switch(TPS) tells the ECU that the throttle is fully closed, and that the TPS is out of adjustment somehow and not quite closing ???


    IF something like crud was causing the throttle to not close as far as fully closed but not letting air in either, a quick way to maybe bully it closed would be to slam it shut, by pressing the throttle full way and slipping of it allowing it to spring back with as much force as possible.
    It is worth a try in absence of any diagnostic computer to plug into and it'll give you something to do while you are revving.
    The great thing about the diagnostics is these things often go bling in front of you and you dont have to mess about with things that aint broke yet.
    Jo
    Thanks. Will keep it in mind and visit this after checking out the idler stepper motor
    1998 Peugeot 406 D8SV Manual
    1999 Peugeot 406 D8ST Auto
    2002 Peugeot 406 D9SV Manual
    1994 Peuegot 306 N3 Cabriolet Manual
    1994 Peugeot 306 XR N3 Hatch
    1995 Peugeot 505 GTI executive
    1976 Peugeot 504 Sedan - Now sold

    Over 60 Pugs in my time
    Gerry Mullock

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