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Mercedes-Benz engine repair questions and answers

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  • johnchar393
    johnchar393 - 1984 Mercedes Benz 300TD - Engine - 8/27/2013
    Where on the engine do I install the block heater for this car?
    heater mercedes benz part no is Q6200009
  • don.spears
    don.spears - 1988 Mercedes Benz 560SL - Engine - 8/14/2013
    Cold idling black gas smoke out tailpipe, black smoke reduces when engine warms
    Revving when engine will produce a little black smoke. What is the mechanism that increases gas for cold starts then reduces for warm run? On old carb cars it was an automatic choke. This car has fuel injection.
    • wbrockstar
      8/14/2013 wbrockstar
      On your model of car,the only two sensors that have that job are
      1) O2 - Oxygen sensor
      2) ECT - Engine Coolant Temperature sensor
  • UCME48
    UCME48 - 2001 Mercedes Benz SLK320 - Engine - 8/13/2013
    What woud cause a ECU to fry and smoke
    I pulled in a driveway and hit a bump and the car went into limp mode, i shut it off and then tryed to start it , it started one and never started again, it smoked the ECU computer.
    • wbrockstar
      8/13/2013 wbrockstar
      Theyre designed to take a lil bit of vibration and bumps so thats odd.Something inside the ecu couldve jarred loose.The wiring harness
      to ecu might have a bare wire that shorted on metal when you hit bump.There are a few resistors inside ecu that have been known to burn up rite where they meet circuit board.Moisture couldve been in the near by viscinity,bump could have jarred the case loose enough for moisture to seep in.Too much voltage couldve also burnt it up as in a sudden unexpected surge of voltage.The ecu works off of very small voltages( 5v) and if any circuit on the car shorted to/through ecu,it would fry because everything not related to the ecu on the car works on ( 12 volts)....You cant pass 12v through a 5v circuit
      8/14/2013 UCME48
      I think u ht it with the surge. would a short do it also? what would be the best way to track t down if there is any,,?? thanks for your help i really apperiate it.
    • HouseCallAuto
      8/13/2013 HouseCallAuto
      Is the area the computer is in look like there is or has had water intrusion?
  • micheleadibe
    micheleadibe - 1992 Mercedes Benz 300SE - Engine - 7/31/2013
    Why is my car over heating
    after 4 miles it over heats, it started two days ago
    • wbrockstar
      7/31/2013 wbrockstar
      Low coolant in system,thermostat stuck in closed position(a good test to check is,turn heater on when engine starts to overheat,if its blowin only luke warm instead of hot,thermostats stuck-replace) Malfunction in cooling fans.Radiator could be clogged.Faulty water pump.Faulty radiator cap failing to maintain proper pressure on cooling system
  • wendald clark
    wendald clark - 1997 Mercedes Benz SL320 - Engine - 7/30/2013
    Engine starts then shuts off emediatly
    Turns over then dies
    • frankiedonnn
      7/30/2013 frankiedonnn
      If it stalls as soon as you take your hand off the key sort of thing check the ballast resistor.Also check intake manifold for leaks, insufficient fuel flow check fuel pressire and fuel filter : if the fuel filter is not in the tank it maybe easy to do this yourself .No point in dropping the tank unless you are sure of the diagnosis.
  • nilo
    nilo - 1980 Mercedes Benz 280SE - Engine - 7/29/2013
    What could be wrong with my 1979MB 280SE, Hard to start esp. for the first time, seem no have insufficient supply of gas
    I need to put little gas in the carb so it starts easier for the first time. But after travelling about 20km its hard to start again.
    0 answer
  • daystrom1
    daystrom1 - 2006 Mercedes Benz S430 - Engine - 7/28/2013
    The RPMs are revving too high when I drive the vehicle. The closer the speed gets to 50 mph the RPMs move between 5 and
    The closer the speed gets to 50 mph the RPMs move between 5 and 6 and the vehicle starts shaking.
    0 answer
  • fsampa2002
    fsampa2002 - 1997 Mercedes Benz E320 - Engine - 7/17/2013
    I kept on getting a service overdue message and exhaust temperature high,the car has just stopped .
    wenever i want to start the car,the engine cuts.wat cud be the problem?
    • wbrockstar
      7/17/2013 wbrockstar
      The exhaust temp bein high is suspect.Clogged converters can cause this and when they go bad the car wont start due to exhaust bein restricted.Do you know what service is actually overdue
    • fsampa2002
      7/17/2013 fsampa2002
  • braswellvp
    • HouseCallAuto
      6/22/2013 HouseCallAuto
      You or anyone else is not gonna figure this out without knowing what fault codes are stored in the ecu. You must check for codes, that means connecting an appropriate scan tool to the diagnostic connector and reading the fault codes. Skip that step and this is just a game of guesswork and throwing parts at it. You can do a visual check and make sure that there are no vacuum leaks caused by a cracked or disconnected hose but beyond that this is not gonna get figured out without data.
    • rickettsgeorge
      7/16/2013 rickettsgeorge
      car not starting but idies engine not turning on
  • grinor00005
    grinor00005 - 2000 Mercedes Benz S500 - Engine - 7/13/2013
    My car has been sitting up for about a year, the lights are flashing an it wont start
    it has 103,000 miles, I changed the battery, an it still wont start
    • Jimm
      7/13/2013 Jimm
      Need more information - what is meant by 'it won't start'? Does this mean the starter motor does turn when the ignition key is turned? Does this mean the stater motor does not turn when the key is turned? Does this mean the stater does work, yet the engine will not run?

      Please clarify what is meant and provide as much detail as possible for further assistance.
  • andrebritt
    andrebritt - 1993 Mercedes Benz 300E - Engine - 7/13/2013
    Sometimes my car will lose power and wont excelerate,but if I turn the car off,let it sit for a few mins,hrs it runs
    227k,all the plugs,belts have been changed.this problem may occur every other month depending how much I drive it.when it occurs and I take it to the mechanic nothings wrong cause the car starts running fine feel like the car is not getting enough gas or ...
    0 answer
  • Punch_Products
    Punch_Products - 1998 Mercedes Benz C230 - Engine - 7/12/2013
    Service engine light on
    mechanic check and said p170 code oxygen sensor bad not sure which one how many sensors are there
    • Jimm
      7/12/2013 Jimm
      There are two (2) oxygen sensors on the 2.3L engine and exhaust system - one upstream and one downstream of the catalytic converter. Usually, if one O2 sensor is faulty - go ahead and replace both at the same time due to age / mileage and wear considerations.

      Check the following auto parts sources for the replacement parts;,, - to list only a few possible sources. For example, they (RockAuto) list the O2 sensor (either up or downstream position) from around $21.00 each for your vehicle.
      These are very simple to replace - check the 'How-To-Guides' feature on the AutoMD website for more installation details.

      P0170 means Fuel Trim Malfunction (Bank 1). P0170 indicates a malfunction in the PCM control of the air-fuel ratio. Bank 1 is the side of an engine that has cylinder 1.

      Possible Causes:

      Dirty or defective MAF sensor
      Vacuum leak
      Defective fuel pressure regulator
      Defective O2 sensor
      Oil contamination in the cam/crank sensor wiring or MAF/O2 sensor connector

      Possible solutions:

      Clean or replace MAF sensor
      Replace fuel regulator
      Replace damaged or cracked vacuum hoses
      Clean cam/crank sensor wiring or MAF/O2 sensor connector
      Replace O2 sensor
  • psales11
    psales11 - 2000 Mercedes Benz S500 - Engine - 7/11/2013
    The car will not start when it is hot and it cut off while driving
    It happens when the care is hot and when the car rest for about 30 minutes it starts. The car engine cut off while driving.
    • CVO
      7/11/2013 CVO
      The check engine light doesn't have to be ON to store a fault code.

      Check the vehicle for fault codes to see if there are any sensors were involved to the malfunction of the engine.

      1.Local auto parts stores such as Autozone ( not in California) or Advance Auto parts will scan and retrieve any diagnostic trouble codes ( dtc ) stored in the powertrain control module for free of charge..

      2. has the code reader for 17.10 dollars+ shipping.

      3.Re-post the dtc's in here " answer question " for further assistance.
      Autel MaxiScan MS300 CAN Diagnostic Scan Tool for OBDII Vehicles

      Note: we need the dtc's to identify the sensor, there are a dozen different sensors to operate the car.

      Visit this site and see all the different sensors.

      Note: the symptom described, it fitted for the camshaft position sensor, check it.
  • carlito
    • Jimm
      6/29/2013 Jimm
      Ther is no float adjustment - as was previously found on engines with carburetors.

      Under your air cleaner mounted to the side of the fuel distributor is your EHA valve. I would like you to disconnect the plug on the valve when the engine is running poorly and see if the engine smooths out. The valve controls your fuel mixture. If the engine runs better with the EHA disconnected I'd suspect a problem in the engine management circuit. Do not disconnect the EHA when the car is cold or the cold running will suffer.
      A faulty oxygen sensor can cause the fuel mixture to go rich. Disconnecting the EHA will tell you if the computer is trying to richen the mixture. Try the many on-line auto parts sources, such as;,, - to list only three - for the oxygen sensors or any other replacement parts.
  • crawfordtosha
    crawfordtosha - 2005 Mercedes Benz C240 - Engine - 6/25/2013
    What cause a car to shut down at red light and start back up
    0 answer
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