Help needed with OM651 intermittent stutter, smoke, and clicking noise
Posted: Fri May 08, 2026 2:27 pm
Greetings everyone,
The OM651 engine is in my 2013 Mercedes C200 CDI. When accelerating between 1,000 and 2,500 RPM, the vehicle occasionally stutters or hesitates. Sometimes everything works well, and then all of a sudden it starts acting up again.
From what I've observed:
• Restarting the engine sometimes makes it appear better.
Why After first appearing to resolve the issue, cleaning the MAF and MAP sensors did not prevent it from returning.
• It made no difference to disconnect the MAF and MAP while the stutter was occurring.
Seems like the fuel pressure is OK.
Pressure boost appears to be normal as well.
• When it stutters, I notice smoke and a diesel/oil odour.
A clicking or clacking sound, as if the engine were trying to provide more gasoline or something was producing noise under stress, is audible when I apply a heavy push on the pedal.
• I have suspicions that the DPF and EGR are either eliminated or circumvented.
• I'm not sure whether something is amiss with the EGR/vacuum configuration because I don't have the vacuum box that goes on top of the EGR cooler.
Since then, my suspicion has shifted from the MAF/MAP to the injectors, the seals around the injectors, a vacuum or air leak, or an issue with the EGR or boost control system.
Does anyone have experience with symptoms similar to OM651? Notably:
only experience stuttering when subjected to stress,
• Smoke that smells like fuel or oil,
• Sound of clicking or clacking when speeding up,
Disconnecting MAF and MAP does not result in any noticeable difference.
• Delete or bypass DPF/EGR systems in vehicles?
After that, what would you look for?
The OM651 engine is in my 2013 Mercedes C200 CDI. When accelerating between 1,000 and 2,500 RPM, the vehicle occasionally stutters or hesitates. Sometimes everything works well, and then all of a sudden it starts acting up again.
From what I've observed:
• Restarting the engine sometimes makes it appear better.
Why After first appearing to resolve the issue, cleaning the MAF and MAP sensors did not prevent it from returning.
• It made no difference to disconnect the MAF and MAP while the stutter was occurring.
Seems like the fuel pressure is OK.
Pressure boost appears to be normal as well.
• When it stutters, I notice smoke and a diesel/oil odour.
A clicking or clacking sound, as if the engine were trying to provide more gasoline or something was producing noise under stress, is audible when I apply a heavy push on the pedal.
• I have suspicions that the DPF and EGR are either eliminated or circumvented.
• I'm not sure whether something is amiss with the EGR/vacuum configuration because I don't have the vacuum box that goes on top of the EGR cooler.
Since then, my suspicion has shifted from the MAF/MAP to the injectors, the seals around the injectors, a vacuum or air leak, or an issue with the EGR or boost control system.
Does anyone have experience with symptoms similar to OM651? Notably:
only experience stuttering when subjected to stress,
• Smoke that smells like fuel or oil,
• Sound of clicking or clacking when speeding up,
Disconnecting MAF and MAP does not result in any noticeable difference.
• Delete or bypass DPF/EGR systems in vehicles?
After that, what would you look for?