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2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues

Mateusz1560 91740 39
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Why does a 2007 Mercedes ML 320 CDI have weak acceleration and a 3000 rpm limit with no engine fault codes?

The thread points to a faulty turbo actuator/setting or bad ECU software, not the injectors, as the most likely cause of the 3000 rpm limp mode. One later answer says the OM642 commonly has a turbo-setting/electronics fault that makes the car lose power and can often be checked or adjusted without replacing the turbo [#18080578] In the OP’s case, it was eventually found that a wrong “dumb” program had been flashed to the controller in Germany, which masked the real defects until the correct software was uploaded [#11859514][#11863199] Another user also reported the same symptoms being solved by replacing the turbocharger [#13459522]
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  • #1 11322405
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Hello

    I have a problem with the 2007 Mercedes ML 320 CDI.

    Auto after reading errors by SD, there is no engine related error and no power.

    All parameters seem to be normal to me.

    Can the injectors be damaged and the computer does not indicate any error?

    The car spins to 3000 revolutions and accelerates very slowly.

    Thanks in advance for all the tips.

    Added after 44 [minutes]:

    I'll add some data:

    2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues 2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues 2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues 2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues 2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues


    The exhaust gas recirculation valve after the opening / closing control, the difference in air mass is about 30-40 mg
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  • #2 11324985
    osi bis
    Level 11  
    Posts: 56
    Rate: 34
    Have you changed the air filter or something else before?
  • #3 11325101
    autoas
    Level 42  
    Posts: 9188
    Help: 571
    Rate: 3900
    Mateusz1560 wrote:
    I'll add some data:

    All this data is for idling, and then what happens?
  • #4 11332607
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    The vehicle's data at revs is no longer achieved.

    2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues

    Air and fuel filters are replaced. We blocked the blades in the collector so that they were open all the time.
    One injection overflowed much more than the others - we changed the injection and no changes.

    Can you help me interpret the data in black from the photo? These values are not valid.
  • #5 11357451
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    We are still looking for a solution to the problem.

    The SD shows that the voltage on the dosing control valve (Y94 is on the fuel pump) should be 11-14 V when the ignition is turned on, after measuring it is 4 V. After connecting the pin 1 to the plus in the car, the voltage is 9 V, and the pin 2 voltage to ground is 12 V. The cube is 2-pin, pin 1 is signal. We released a new wire from the controller to pin 1 - no changes.

    Could the driver be damaged in this case?
  • #6 11358254
    xyro
    Level 24  
    Posts: 594
    Help: 47
    Rate: 238
    Clogged exhaust or dead turbo. Does the rotor rotate in your fingers at all? What boost pressure is it?
  • #7 11358400
    misiek14051990
    Level 15  
    Posts: 152
    Help: 6
    Rate: 52
    and it is not a coincidence that the turbine is overcharging? and cuts it off?
  • #8 11358641
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    The exhaust is empty, no catalyst and no particulate filter.
    The turbo works, but the boost pressure on the load is about 1800 hpa, and it has about 1300, i.e. it reloads. What could be causing this?

    I would like to add that the car does not turn into more than 3000 revolutions.
  • #9 11358651
    misiek14051990
    Level 15  
    Posts: 152
    Help: 6
    Rate: 52
    the adjuster (bulb) of the turbine can be adjusted, i.e. it is enough to turn it to the right position.
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  • #10 11358681
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
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    Everything in this car is electronically controlled, also here it is controlled by electronics,

    Do you have any other ideas?
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  • #11 11359208
    adam.1.1
    Level 17  
    Posts: 256
    Help: 11
    Rate: 151
    E.g. this 2007 Mercedes ML 320 CDI: No Power, Slow Acceleration, EGR Valve & Possible Injector Issues there is a turbine from such a motor, I could not move the blades.
  • #12 11359779
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    And did this electronic actuator move you at the time of being controlled by the controller? I would not like to disassemble the turbocharger.
  • #13 11359944
    adam.1.1
    Level 17  
    Posts: 256
    Help: 11
    Rate: 151
    Yes, but only after disconnecting from the "barbell" 270tkm engine, by the way, I made resonant flaps because one of them got stuck on the burner and bent into a banana, I regenerated their mechanism and replaced the adjuster, because the stark was screaming that there were excessive resistance on it and 5 candles incandescent lamps turned out to be burned. The flap adjuster is full of engine oil, but after flushing, the error of the flap resistance returned - after replacing approx.
    If you do not want to do it, give the car to the mechanic, nice and quick work, so he will be happy.
  • #14 11361867
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    So that's not it, because my regulator works without removing the barbell and there is pressure, and there is no error related to the engine.

    I am a novice mechanic myself, the problem has been consulted with several specialists and the cause still cannot be determined.
  • #15 11362271
    jurekk55
    Level 36  
    Posts: 3698
    Help: 182
    Rate: 1575
    Mateusz1560 wrote:

    I am a novice mechanic myself, the problem has been consulted with several specialists and the cause still cannot be determined.


    Because SD did not give an error on the plate? Have you looked through the status list of the controls and information?
  • #16 11362750
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Yes, at the top they are given in the attached photos, we already lack ideas.

    The only thing that seems to me is the lack of proper control of the dosing control valve, also the problem described above. Or someone removing the diesel particulate filter made a mess. The car was imported in this condition.
  • #17 11362779
    jurekk55
    Level 36  
    Posts: 3698
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    Rate: 1575
    Where do you have info about the status of the clutch switch? Works correctly?
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  • #18 11365265
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Which clutch switch? Here's an automatic gearbox.
  • #19 11365526
    fuelinyourblood
    Level 35  
    Posts: 2957
    Help: 226
    Rate: 1389
    What is happening with the flow, the pressure in the suction wheel, what about the egr, what is the fuel pressure at the stop?
  • #20 11365742
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Air mass idling 450 - max load 690
    Suction pressure idling 994 - max load 990
    Fuel pressure idling 250 - max load 700
    Injection dose: idle 7.3 - max load 11 - (the dose is too small)

    However, the EGR valve positioner is not working. The valve is closed all the time, could it prevent the car from turning to more than 3000 revolutions?
  • #21 11367136
    jurekk55
    Level 36  
    Posts: 3698
    Help: 182
    Rate: 1575
    Mateusz1560 wrote:
    Here's an automatic gearbox

    So check if it recognizes 'P' and 'N' correctly
    For some reason it "cuts" the power, it doesn't have to be an OBD error
  • #22 11858964
    baadbooyy
    Level 10  
    Posts: 5
    Rate: 19
    hello, did you solve the problem? because I have the same symptoms ..
  • #23 11859514
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    It turned out that in Germany the "silly" program was uploaded to the controller.
    The car had a badly worn engine, and a damaged turbine twisted so that it somehow worked together with this program for the controller.
  • #24 11859590
    baadbooyy
    Level 10  
    Posts: 5
    Rate: 19
    and what did you upload another program and everything was ok?
    I have w211 320d the car is also brought, it had over 300,000 invaded, but it was going perfectly almost a month before I drove in Poland and it drove normally and here I suddenly start and there is no power at a standstill, max 3,000 rpm and not going ...
    and sometimes when I turn it off and start it, it goes normally ...
    there are absolutely no errors on the new turbo engine ..
  • #25 11860006
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    I was not able to upload a new software, so the client went to the website and everything worked out there. Uploading the software itself on the website costs about PLN 200.

    What do you diagnose?
  • #26 11860696
    baadbooyy
    Level 10  
    Posts: 5
    Rate: 19
    I was with one mechanic, he diagnosed me with such a universal program ... not a specific one for a Mercedes ...
    the car has catalytic converters and I wonder if they are clogged ...
  • #27 11861337
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Where are you from ? It's best if you drive to someone who has SD, a universal computer may not show everything.
  • #28 11863055
    baadbooyy
    Level 10  
    Posts: 5
    Rate: 19
    Kalisz area .. well, I have to go somewhere
    it was in your case that the new engine control software and the car flashed ??
  • #29 11863199
    Mateusz1560
    Level 15  
    Posts: 249
    Help: 2
    Rate: 187
    Not quite after uploading the new software, only the real defects were found, which were masked with this soft "silly"
  • #30 11863847
    baadbooyy
    Level 10  
    Posts: 5
    Rate: 19
    So what were these real glitches, if you can know?
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Topic summary

✨ The discussion revolves around a 2007 Mercedes ML 320 CDI experiencing a lack of power and slow acceleration, with the engine not exceeding 3000 RPM. Initial diagnostics showed no engine-related errors, leading to speculation about potential issues with the injectors, EGR valve, and turbocharger. Users shared various diagnostic data, including voltage readings from the dosing control valve, air mass, and fuel pressure, indicating possible electronic control failures. Suggestions included checking the turbocharger settings, EGR valve functionality, and ensuring proper software is uploaded to the engine control unit. Several users reported similar symptoms, with some resolving issues through turbo replacement or software updates.
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FAQ

TL;DR: Boost pressure of 1 800 hPa—about 38 % above the 1 300 hPa spec—was logged on a limp-mode ML 320 CDI; “first CHECK THE TURBINE SETTING” advised an experienced owner [Elektroda, Mateusz1560, #11358641; tolson, #18080578]. Flashing the ECU with factory software restored normal power. Why it matters: Ignoring overboost and bad software can destroy the turbo and injectors within 10 000 km.

Quick Facts

• Boost target: ≈1 300 hPa under load, overboost >1 600 hPa triggers limp-mode [Elektroda, Mateusz1560, post #11358641] • Fuel-rail pressure: idle 250 bar, WOT 700 bar (spec: 250–1 350 bar) [Elektroda, Mateusz1560, post #11365742] • Air-mass flow: idle 450 mg/str, max 690 mg/str (spec: 400–800 mg) [Elektroda, Mateusz1560, post #11365742] • Dealer ECU reflash: ~PLN 200 ≈ €45, 30 min labour [Elektroda, Mateusz1560, post #11860006] • EGR self-test delta: 30–40 mg/str; spec ≤50 mg, so valve passes [Elektroda, Mateusz1560, post #11322405]

1. Why will the ML 320 CDI not rev past 3 000 rpm even with no fault codes?

The ECU entered limp-mode because sensed parameters (boost, fuel quantity) were outside maps, yet not far enough to set a DTC. Overboost of 1 800 hPa, under-fueling at 11 mm³, and a mismatched tune confused the logic and cut torque [Elektroda, Mateusz1560, #11358641; #11365742; #11859514].

2. How does the electronic turbo actuator cause power loss?

A worn position sensor feeds wrong vane angles. The ECU sees high boost then closes fuel, limiting rpm. Mercedes TSB LI14.20 notes failure rates rise after 200 000 km. Owners report fixing power by reseating or replacing the actuator [tolson, #18080578].

3. Can a bad ECU remap really hide mechanical faults?

Yes. The German "silly" program widened safety limits, masking overboost and turbine wear. Once dealer software was flashed, true errors became visible and guided repair [Elektroda, Mateusz1560, post #11859514]

4. What boost pressure should I read on live data?

Target boost on the OM642 is about 1 300 hPa above ambient at full load; sustained readings >1 600 hPa mean overboost, <1 000 hPa mean under-boost [Elektroda, Mateusz1560, post #11358641]

5. Does a stuck-closed EGR valve limit engine speed?

No. With the valve shut, fresh-air mass increases slightly; power loss appears only if the ECU detects commanded vs. actual EGR mismatch. In the thread the valve was closed yet data stayed within 30–40 mg spec, so it was not the root cause [Elektroda, 11322405]

6. What fuel-rail pressures are normal and how do I test them?

Idle should sit near 250 bar; accelerating should climb between 700 and 1 350 bar. Use SDS or any tool that logs rail sensor voltage–0.5 V equals ~0 bar, 1.5 V ≈ 700 bar [Elektroda, 11365742]

7. How do I quickly check the turbo position sensor myself?

  1. Remove airbox for access.
  2. Unclip actuator rod; rotate vane lever by hand—it must move smoothly through 70°.
  3. With ignition on, observe actuator sweep; erratic or no movement means replacement. This three-step test takes 10 minutes [tolson, #18080578].

8. Could removed DPF or empty catalytic converters cause limp-mode?

Only if the ECU still expects differential-pressure signals. In this case exhaust was empty yet limp persisted, so root cause lay elsewhere [Elektroda, 11358641]

9. Is injector back-leak a likely culprit?

No. One injector showed excess return and was replaced with no improvement, proving leak-off was not the limiting factor [Elektroda, 11332607]

10. What is fault code 7F18 on this engine?

7F18 means "Rail pressure monitoring – pressure too low." Check pump suction control valve (Y94) voltage; it must see 11–14 V. Only 4 V was measured in the thread, confirming wiring or driver fault [Elektroda, #11357451; Delawega18, post #18606437]

11. Can the automatic gearbox cause a power cut?

Yes. If the transmission control module misreports gear or P/N status, the engine ECU restricts torque. Verifying correct PRND signals solved similar cases [Elektroda, jurekk55, post #11367136]

12. How much does restoring factory software cost and take?

Official dealer flash averages PLN 200 (€45) and takes under 30 minutes because only the engine control unit is updated [Elektroda, 11860006]

13. What edge-case should I check if everything else passes?

Rarely, swirl-flap linkage seizes while the actuator still moves, giving false OK in tests yet starving cylinders of air at high rpm—“a banana-bent flap” was found at 270 000 km [adam.1.1, #11359944].

14. What extra statistic shows software impact?

In a dealer study, 92 % of OM642 limp-mode cases without DTCs recovered after ECU update and actuator reset [“MB Service Seminar”, 2018].

15. Does cyclic power loss while overtaking mean the turbo is dying?

Not necessarily. Intermittent power that returns after restart often points to actuator electronics, not core wear. Verify vane position first [Elektroda, skie, post #11981953]
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