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cheapohubby

Cleaned EGR, but still getting P0405, limp mode and sputtery start...

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I finally got around to pulling the EGR valve and cleaning it (been getting the code for over a year).  It was definitely plugged up with gunk; but I think I got it cleaned out.  But Darth is persisting to complain about the P0405 code, still suffers limp mode (refuses to go beyond 3300 RPM) and still sputters a lot on a cold start in the morning.  So, basically he's behaving exactly the same as prior to the cleaning.  I'm pretty sure I put the valve back in the correct orientation.  It was and the actuator were moving freely.  Any thoughts on what to check?

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Posted (edited) · Report post

Remove the 3 hex bolts to separate the electrical solenoid part of the EGR valve. The plunger should move freely and spring loaded. If its stuck inside the solenoid, or does not pop out smoothly, it maybe the issue.

 

Good luck!

Edited by stickman007

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Pulled the valve again, and found some more chunks of crud (obviously didn't do the best job of cleaning it out in the first place).  Inserted the valve and confirmed that the valve moved freely and that it was having an effect on the engine when running (engine got spluttery when I pushed in the valve).  Solenoid moves freely too.  Re-attached the actuator and had a short interval without limp mode, then it returned.  Pulled it apart again, but couldn't see anything to cause a problem.  

I've pulled the actuator off a few times since then (getting pretty good at blindly undoing those allen screws!), and now it seems to be getting to the point where it sometimes pops out of limp mode.  Not sure if it's something glitching (actuator or connector), or if it's just the engine computer unsure about things.  I'll give it a few days and see if things change one way or the other.

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Posted (edited) · Report post

I don't know whether the following is your problem, but it might be worthwhile trying an emulator.

 

The ECU knows where the EGR solenoid is from a variable resistor attached to the EGR solenoid which feeds back current comparing the solenoid's position to where it has been commanded to be.

 

If the variable resistor is worn or the wiper on the resistor bounces, this can cause limp mode to occur.

 

Mercedes sells a short interface cable (the connectors from which are frequently used to connect to emulators) with an additional 470K Ohm resistor placed across (in parallel) with the variable feedback resistor which was likely designed to overcome this problem.

 

This is one reason why I feel that an emulator is a better solution than a blanking plate or rotating the EGR barrel. The feedback variable resistor can still wear and cause limp mode.

 

With an emulator, the feedback resistor is inactive and the emulator provides the feedback.

Edited by smartdriver

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I started to wonder if it might be the actuator.  Maybe the feedback resistor as you mention; or maybe the connector.  So the next thing to try was swapping the actuator from Squish (Squish is currently parked for the summer until I get around to working on the steering column).  Well; it looks like that's resolved things.  No sign of limp mode since the swap, and it's been out for a test drive.  The only code left to deal with is the P0380 (glow plug).  I guess I need to add a replacement EGR valve actuator to my list of parts to pick up next time I'm in Halifax.

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