Another case of the engine hunting at idle when warm, can anybody help?
An A180CDI 2ltr 2009 Diesel Auto. When the engine warms up the idle intermittently Hunts. I've removed the airbox and have piped the vacuum system to run without it (for observation). The problem remains.
I've checked all the vacuum pipes and cannot see any evidence of leaks. I've removed the EGR valve and body and Throttle body (pig of a job) and have cleaned them until they were like new. The problem remains!
Disconnecting the EGR vacuum solenoid immediately cures the lumpy idle. Alternatively, removing the vacuum pipe to the EGR valve cures the problem. Finally, unplugging the MAF also stops the intermittent lumpy idle.
The only clue I have is that when the rough idle appears the Duty cycle reading for the Y31/13 (EGR [ARF] vacuum transducer / throttle valve) starts jumping all over the place. But no fault codes are ever thrown up!
I would appreciate any help anybody could offer with this, its driving me bonkers.
Many thanks, Gerald.