Technical Brief revving up every minute on idle

[RayF]

Hello Fiat Forum!
My engine is idling normally, but approx. every minute, it briefly revs up for a second or two before returning to normal. This is happening both after cold starts or warmed up, no difference. Also noticed at highway speeds, very occasionally the engine stalls for a very brief moment but only when the engine pulls either at higher speeds or when climbing, but again, this is very rare not like the idle revving. I am clueless where to start looking.
2007 Ducato 3.0 160 Multijet
Attached a sound file, the revving can be heard at 0:30 and at 1:30.
Many thanks for help.

 

[The Panda Nut]

May be air an leak in the fuel supply line, Possible the filter not sealed as it should.?

 

[RayF]

Thank you for responding. Had a scanner read out code P0638 Throttle valve command/open circuit/intermittent which could be the solenoid, the actuator itself or the wiring(?) My engine bay suffers from the dreaded water leak problem too. Will investigate further.

 

[Anthony489]

Hi

A 2007 Ducato is likely to have been factory fitted with a Wahler throttle body on the inlet manifold. The electrical part of this is not well sealed, and most of these by now will have had water ingress, rusted up and been replaced. If you still have an original Wahler, I suggest you check it out.

The other (much less likely) possibility is that the idle speed is being raised by the ECU to counteract a low vehicle (starter) battery voltage for some reason. If this is the case, the Battery/Charge warning light will be activated.

 

[RayF]

update: throttle body was the original Wahler, dust had accumulated inside but not too much, the flap did not return to original position firmly. Throttle body was replaced, now van runs much better but original problem still persist, the engine idles normally but every minute a very brief (less than a second) rev up. Fault code disappeared however...

 

[RayF]

Problem sorted: EGR was blinded and the solenoid was not properly piped which caused not just the solenoid going bad but also the gasps on idle trying to transmit exhaust. Check engine went away after EGR setup correctly with piping as it should. Thanks for everyone on support.