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check engine light

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Chas, Oct 29, 2012.

  1. Chas

    Chas Senior Member

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    Your Mercedes:
    S320
    S class W220 2001 S320 petrol 2001, 95k miles

    My check engine light is on and car is in limp mode ( reduced power)

    It starts ok and revs are stable ( Full MB service history)

    Any any ideas? Its petrol so no EGR valve, could it be a dirty blocked intake manifold?
    I have disconnected battery and it clears the check engine warning light temporarily, it reappears the next day !

    Thanks
     
  2. Cole@MBS

    Cole@MBS Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
    124 300 CE 24 Coupe, 209 240 CLK
    Airmass or a pair of leads to start the guessing off, you no we want fault codes Chas.......
     
  3. OP
    Chas

    Chas Senior Member

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    Thanks, taking car to MB tech this week :) Will let you know outcome ...
     
  4. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Yes the MAF is a good one to start with, this does not turn the lamp on, it is the O2 sensor when it tries to compensate.

    How is life young man
     
  5. OP
    Chas

    Chas Senior Member

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    Life is good Malcolm, took early retirement two years ago, never looked back:D

    Spend most of my time with wild life photography http://www.wildfeathers.co.uk , and enjoying the free time with my family

    Hope all is well with you too Malcolm?

    I suspect its the MAF,had a word with MB tech independent, great guy local in Ayr, Jon Thomson ex tech manager at MB dealers, he is picking the car up this week to test drive and then diagnose

    Will let you know the outcome
     
    Last edited: Oct 30, 2012
  6. OP
    Chas

    Chas Senior Member

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    Hi Malcolm

    Just a quick question if you have time. These things annoy me and I like to sort them myself :D

    I unplugged the MAF and symptoms were exactly the same as before.

    Engine starts fine from cold, revs at 1200 for 10 secs or so , then revs drop to 800

    Foot on pedal, revving up fine full power, 10 secs later back to reduced power mode

    Does this mean

    A. The MAF is faulty

    B. The MAF is ok and something else is faulty..........0 2 sensor ?

    Thanks again Malcolm

    Chas :D
     
    Last edited: Oct 30, 2012
  7. television

    television Always remembered RIP

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    Your Mercedes:
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    If there is no change with it unplugged, then I think we could say it is faulty.

    The MAF sets up the fuelling according to the temp, when the MAF fails the 02 sensor tries to compensate, now the 02 sensor is coded to the engine and works within a set + or - element, if it shifts too far from its stored setting, this turns on the warning lamp, most lamps will turn off on their own after a few hard drives and the original fault corrected.

    As always I would hate you to buy something that you did not need, so what do you do. The cheapest place to buy one is from any Bosch service center
     
  8. OP
    Chas

    Chas Senior Member

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    Thanks Malcolm

    I will let the tech guys diagnose the fault. I can get a new Bosch MAF £170 or cheaper one for £50 with 1 year gaurantee

    When did you go "CL" What happened to your wonderful SL ?
     
    Last edited: Oct 30, 2012
  9. television

    television Always remembered RIP

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    Your Mercedes:
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    I am looking after my ex now who has severe memory problems,,, and she found it too hard to get in and out of the SL, so I bought a 140 CL420 and then a 216 CL500 , but with 3 cars I am going to sell the CL420, I just cannot drive them all. The 216 is fully loaded with ever toy that you can have, so that keeps me happy:D:D

    I am pleased that you are keeping busy too enjoying what you like to do :D

    MB tech always do not like me for telling folk to change the MAF without a test
     
  10. Argus

    Argus Senior Member

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    I'd be interested in knowing the outcome of this as a pal of mine had the Check Engine Light come on today. Same model and very similar age and mileage. Doesn't mean it's the same fault of course but a good indication for a start.
    I hope yours gets fixed quickly and without too much of the folding stuff from your back pocket
     
  11. OP
    Chas

    Chas Senior Member

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    Jon Thomson, MB tech Indi, Ayr picked up the car this morning at my home, took car in to diagnose fault. Just got a call, it was the throttle potentiometer fault code. He cleared the fault, started up the car, running perfect !!
    He also got the exhaust bracket welded at the unit next door to him.

    £ 80 for the lot, that is what I call excellent service.
    http://www.automotivesolutionsayr.co.uk
     
  12. television

    television Always remembered RIP

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    Thanks and nice to know that one
     
  13. Miffy

    Miffy Senior Member

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    Your Mercedes:
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    When mine went it displayed a very differnt error. MIL came on and throttle responce was very poor. But it would still get to a decent speed

    Sent from my GT-I9300 using Tapatalk 2
     
  14. OP
    Chas

    Chas Senior Member

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    Update :-(

    Started car this morning, check engine light back on, same symptons as before:(

    Will take car back in to investigate....

    The findings yesterday were" B37 POTENTIOMETER (THROTTLE PEDAL) stored fault, actuation and actual test within spec,
    Cleared fault memory and tested, no fault "

    Wish me luck :D
     
  15. television

    television Always remembered RIP

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    I will say it is the MAF but then I always say that :D:D
     
  16. OP
    Chas

    Chas Senior Member

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    Watch this space Malcolm :)

    ps

    I am told a car will run fine temporarily with MAF disconnected, whether it is ok or faulty. If the MAF is faulty the car wont run ok when plugged in :)
     
    Last edited: Nov 2, 2012
  17. OP
    Chas

    Chas Senior Member

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    Update

    I disconnected the battery for an hour, reconnected, started her up and engine check light not showing, but still reduced throttle power. Switched ignition off, took key out, started her up again and running perfect :D

    Must be one of those annoying electrical things ?

    Will keep you updated ;)
     
  18. television

    television Always remembered RIP

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  19. OP
    Chas

    Chas Senior Member

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  20. television

    television Always remembered RIP

    Messages:
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    Your Mercedes:
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    Its a switchable fault the MAF but I get teased on this,,,, I have been right though oodles of times
     

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