Technical EGR Fault P0404-78 Excessive offset

[Busso]

Hi all,

I've got a fault code that keeps flagging up every so often, mostly from cold. P0404-78 EGR Excessive offset.

Car drives fine but does throw smoke out for first few seconds from cold. I've had a look at MES and a couple things stand out. First MAF air temp is -40. It might be an anomaly as when started it reads fine. Secondly EGR is open 9% on idle when warm. I assume it's meant to be closed so valve could be stuck open?

It was thoroughly cleaned out around 3k miles ago so I would like to understand the fault code more before removing it again (It's an absolute pig of a job)

Any knowledge is appreciated, thanks

 

[Busso]

Just to give an update to this, I removed EGR valve. It wasn't too badly caked up but I tried pouring some fluid into it & it leaked out while closed. I decided to take it apart and used some grinding paste to lap in the valve to give it a good seal. 'Actual EGR position' is now -0.003mm. Hopefully this has fixed the issue.

 

[bunterboy]

Good job, hope that sorts the issue. Well done.

 

[steveras57]

well done glad its sorted!

 

[Busso]

It's not sorted Fault came back first thing this morning. I'm not convinced it's the EGR

 

[steveras57]

It's not sorted Fault came back first thing this morning. I'm not convinced it's the EGR

Thats a real shame after all the good work you did cleaning it up ! i suppose that the valves electrical components might have had it and a new one might be the answer?- however they seem to be quite expensive!!! so swapping out to test might not be practical! wish you all the best sorting it!