Zimbo
Active Member
- Joined
- Jun 22, 2009
- Messages
- 33
- Reaction score
- 1
- Location
- West Sussex
- Your Mercedes
- W203 C220CDI Elegance '04
Hi all,
It's been a while since I've been on the forum but I'm hoping some of you guys can help as I'm puling my hair out with this fault! Longish post but trying to give as much info as possible.
Car is a 2012 W204 C220CDI (149k miles) and was running fine until one morning I started it and it was idling very roughly, sometimes stalling. If I tap the throttle as it starts to stutter then I can keep it running but if I leave it, it stalls. As I was trying to drive it and keep the revs up, the engine light came on and went into limp mode. The only error code is P0401 which is EGR insufficient flow. I'm thinking this error may be more of a symptom than the root cause asit came up after the rough runningbut I could be wrong.
Once the engine warms up after about 5 mins it runs normally apart from being in limp mode. I have been able to reset the error when warm and after a few off/on cycles and get it out of limp mode but it comes back after rough running from cold again and goes back in to limp mode.
Things tried so far after Internet research!
- Tried disconnecting as many sensors/valves that I can reach in case of a faulty one. These bring up a new error code which go away when plugged back in, so I don't think I found one not doing it's job.
- I've done an injector leak off test - not a lot of flow but got a similar amount coming out of each one although two had slightly more than the other two. I've only done this cold, not with a warm engine.
- Changed fuel filter - no change.
- Fitted a (used from breaker) injector rail incase pressure valve or pressure gauge was faulty but this made no change at all. (I really struggled to start the engine after doing this, possibly air lock - flattened the battery a couple of times but eventually managed to bleed the system by sucking diesel up into the rail using a suction pump onto o e of the injector pipes!)
- I then convinced myself that the problem was the Quantity Control Valve/Flow regulation valve Y94 as the car starts fine and then starts playing up after around 30 seconds. Anyway, I spent most of yesterday stripping everything to access this valve and replace it and then reassemble. There was a lot of carbon build up in the EGR pipe to the inlet manifoldand throttle control valve which I cleaned up. Note that I didn't go as far as removing the EGR valve as it looked like even more of a pig of a job and I was running out of time.
It did not fix the problem! It is doing exactly the same thing. Roughidle and P0401 error after a couple of minutes.
I'm now at the end of my tether and may have take it to the professionals. I just don't want to throw money at the car as it's not worth a lot!
Any help/advice gratefully received!
One last question - does anyone e know which sensor triggers the EGR insufficient flow error? I assumed it was the small one on the inlet manifold near where the metal EGR inlet pipe enters? Seems to connect to a venturi hole which I checked was clear after cleaning the manifold.
It's been a while since I've been on the forum but I'm hoping some of you guys can help as I'm puling my hair out with this fault! Longish post but trying to give as much info as possible.
Car is a 2012 W204 C220CDI (149k miles) and was running fine until one morning I started it and it was idling very roughly, sometimes stalling. If I tap the throttle as it starts to stutter then I can keep it running but if I leave it, it stalls. As I was trying to drive it and keep the revs up, the engine light came on and went into limp mode. The only error code is P0401 which is EGR insufficient flow. I'm thinking this error may be more of a symptom than the root cause asit came up after the rough runningbut I could be wrong.
Once the engine warms up after about 5 mins it runs normally apart from being in limp mode. I have been able to reset the error when warm and after a few off/on cycles and get it out of limp mode but it comes back after rough running from cold again and goes back in to limp mode.
Things tried so far after Internet research!
- Tried disconnecting as many sensors/valves that I can reach in case of a faulty one. These bring up a new error code which go away when plugged back in, so I don't think I found one not doing it's job.
- I've done an injector leak off test - not a lot of flow but got a similar amount coming out of each one although two had slightly more than the other two. I've only done this cold, not with a warm engine.
- Changed fuel filter - no change.
- Fitted a (used from breaker) injector rail incase pressure valve or pressure gauge was faulty but this made no change at all. (I really struggled to start the engine after doing this, possibly air lock - flattened the battery a couple of times but eventually managed to bleed the system by sucking diesel up into the rail using a suction pump onto o e of the injector pipes!)
- I then convinced myself that the problem was the Quantity Control Valve/Flow regulation valve Y94 as the car starts fine and then starts playing up after around 30 seconds. Anyway, I spent most of yesterday stripping everything to access this valve and replace it and then reassemble. There was a lot of carbon build up in the EGR pipe to the inlet manifoldand throttle control valve which I cleaned up. Note that I didn't go as far as removing the EGR valve as it looked like even more of a pig of a job and I was running out of time.
It did not fix the problem! It is doing exactly the same thing. Roughidle and P0401 error after a couple of minutes.
I'm now at the end of my tether and may have take it to the professionals. I just don't want to throw money at the car as it's not worth a lot!
Any help/advice gratefully received!
One last question - does anyone e know which sensor triggers the EGR insufficient flow error? I assumed it was the small one on the inlet manifold near where the metal EGR inlet pipe enters? Seems to connect to a venturi hole which I checked was clear after cleaning the manifold.
