S320 W221 exhaust back pressure sensor

Discussion in 'Engine' started by Kay187, Aug 2, 2019.

  1. Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    Hey guys,

    Need some advice - what should the normal values be for the back pressure sensor? I have a S320 cdi w221 model with 137k miles on it.

    Mines are 970mbar when off
    Around 2400mbar when idle
    About 1200-1500mbar when reving around 3k.

    Do these figures look normal?

    Symptoms of car - it's kangarooing with power and I lose kickdown intermittently. Sometimes car runs fine with good power and other times it hesitates to pull like there is a blockage somewhere.

    History
    I've been to a local mechanic as well as an indy who kept getting different codes repeatedly.

    Local mechanic cleaned egr but advised no real fault seen with it. Symptoms were bit better but progressively got worse.

    Indy tested turbo and inlet shutoff motor amongst few others on star and advised turbo actuator faulty. This was replaced with refurbished one which slightly improved intermittency of symptoms but fault still there with different codes pointing to egr valve. This then replaced with a brand new one and codes cleared for a little while but eventually egr valve code came up again. Incidentally all exhaust smoked cleared as sometimes I'd get white smoke from exhausts.

    Dpf not clogged and regens ok. I have a mb carsoft and have confirmed this with the readings I've got on different occasions.

    I've looked around forums for possible fixes and the exhaust back pressure sensor seems to be a possible culprit hence the question.

    I hope someone can help as I've spent quite a lot of money on the car and it still not fixed which getting very frustrating

    Many thanks!
     
  2. OneForTheRoad

    OneForTheRoad Hardcore MB Enthusiast

    Messages:
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    Joined:
    Apr 20, 2015
    Location:
    uk.
    Car:
    2015 w204 c class amg sport premium +65 ford kuga 2.0 cdi zetec awd..
    950 to 1050 at idle. I ran my engine with it removed and still saw stupid readings. There is supposedly a pin hole in the top that gets blocked. I renewed the sensor anyways and it cured my engine. £47 @ mb.
     
    Kay187 likes this.
  3. OP
    OP
    Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    Thanks for confirming the idle readings, that definitely helps :) With the sensor disconnected I was getting around 4500mbar???

    I'll have a look at the said pin hole but for the minor cost I'll just replace it to eliminate. What kind of issues were you having with your car?
     
  4. OneForTheRoad

    OneForTheRoad Hardcore MB Enthusiast

    Messages:
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    Joined:
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    Location:
    uk.
    Car:
    2015 w204 c class amg sport premium +65 ford kuga 2.0 cdi zetec awd..
    Wont rev beyond 3k . Very lumpy. Limp mode no boost . Gearbox erratic.

    Id say yours is toast if its giving readings disconnected.
     
    Kay187 likes this.
  5. OP
    OP
    Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    Yep pretty much same as mines then!

    I don't suppose you have a part number for it?
     
  6. OneForTheRoad

    OneForTheRoad Hardcore MB Enthusiast

    Messages:
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    Joined:
    Apr 20, 2015
    Location:
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    Car:
    2015 w204 c class amg sport premium +65 ford kuga 2.0 cdi zetec awd..
    Ring a dealer cos the numbers change all the time as parts are updated.
     
    Kay187 likes this.
  7. OP
    OP
    Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    Ok will do. Many thanks for all your help, top man :)

    Will update post once fitted.
     
  8. OneForTheRoad

    OneForTheRoad Hardcore MB Enthusiast

    Messages:
    2,115
    Joined:
    Apr 20, 2015
    Location:
    uk.
    Car:
    2015 w204 c class amg sport premium +65 ford kuga 2.0 cdi zetec awd..
    Watch for the metal washer on removal.
     

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