C5 fault codes - Help

johntom · Post by **johntom** » 18 Apr 2011, 22:00

Hi
the engine is back to standard and after several days there are no fault codes. However the juddering/shaking at tickover has now returned as it was before the egr was blocked (wasn't there with the egr blocked), what would cause this ?

cachaciero · Post by **cachaciero** » 19 Apr 2011, 01:22

johntom wrote:Hi
the engine is back to standard and after several days there are no fault codes. However the juddering/shaking at tickover has now returned as it was before the egr was blocked (wasn't there with the egr blocked), what would cause this ?

What you really need is a Lexia to be able to read the associated parameters to find out what is doing what.
BUT logic says that if it idled smoothly with the EGR blanked of then the fact that it doesn't now suggests that the EGR valve is open or partially open.
Now I am not 100% sure of this but I believe that the EGR valve should be closed at idle so I would be checking for a sticking EGR valve, not that uncommon or a duff electrovalve that controls the vacuum supply to it, I would suggest disconnecting the vacuum line to the EGR valve and see if that improves the idle condition, but be aware this will / should give you faults at revs above about 1K revs for reasons already discussed.

cachaciero