Technical 2.2td

[phil071]

Hi everyone I've got a jeep cherokee fitted with what would be fitted to the ducato 2.2td engine are there common problems with the throttle body going wrong ? It's idling at 1050rpm tried every avenue that I know up to yet without rectification no dtcs, throttle body cleaned and reset, o2 sensor replaced, fuel additives n dpf cleaner used, dpf at 40% full, any help would be appreciated, regards phil

 

[LandyAndy]

A throttle body on a diesel can’t raise the speed of the engine. It only controls the air in not fuel.

 

[Anthony489]

Hi Phil

As Fiat and Jeep are both in the Stellantis group it's no surprise that they adopted the Diesel engine from the Ducato for use in the Jeep, albeit in a higher state of tune. I'm assuming yours is the most recent 2184cc Multijet III Euro 6d with Adblue.

The throttle body is part of the EGR system. Unlike a petrol engine it doesn't control idle speed for a diesel. Idling is determined by the amount of fuel injected, which is closely controlled by the ECU. It's normally rock steady at typically 900 RPM regardless of temperature and load from alternator, air conditioning etc.

I can only think of 4 things that would make it higher than normal, though must confess than none of them seem likely:

1.) It's actually 900 RPM but the Tachometer calibration is out
2.) There is a battery charging problem, the ECU is programmed to raise idle to compensate for this. Normally the idle would then be more like 1400 RPM and warning light(s) would show too.
3.) It's performing a regeneration. I think you would notice other clues to this, and it would only happen ocassionally.
4.) The preset fast idle speed has been accidentally programmed - see attached extract from the Ducato 2021 manual

An interrogation of the ECU by a capable diagnostic tool like the open market MultiECUscan or Fiat's proprietary setup should reveal the ECU idle settings.

 

[phil071]

Thank you for clearing up the throttle body as not the problem I will take a look at the preset menu and see what it's saying, how is the menu accessed initially ? It doesn't actually give the description or that's how I read it although I'm a bit dyslexic some times thank you in advance best regards Phil

 

[phil071]

Just noticed theses two readings should it not be 0% ignition on not running and also at idle 1050rpm
Accelerator pedal position d 20%
Accelerator pedal position E 20%

 

[Anthony489]

Hi

Those readings seem a bit high. Worth checking that there isn't some physical cause for the throttle pedal not fully returning.

I don't know if these vehicles have a separate switch to tell the ECU that the throttle is at its upper rest (idle) position, or if it is entirely reliant on the potentiometer readings. If there is a microswitch, check that it is being activated. Should hear a faint mechanical click.

 

[phil071]

Okdoky I'll take a look thank you for your input

 

[phil071]

Okdoky update problem now fixed after an afternoon of head scratching ! Turns out the dpf was blocked despite my other computer telling me it was clear after a regeneration last week....dpf regeneration on a different (new) scan tool cleared the problem moral of the story don't always believe what the scan tool's tell you in live data !!!!!! That applies to both scan tools !!!! complete fluke that I did a regeneration with the new scan tool before I threw a gallon of fuel in with a match ! Thanks for all your input

 

[theoneandonly]

Okdoky update problem now fixed after an afternoon of head scratching ! Turns out the dpf was blocked despite my other computer telling me it was clear after a regeneration last week....dpf regeneration on a different (new) scan tool cleared the problem moral of the story don't always believe what the scan tool's tell you in live data !!!!!! That applies to both scan tools !!!! complete fluke that I did a regeneration with the new scan tool before I threw a gallon of fuel in with a match ! Thanks for all your input

Please what scan tools did you use?
the first
the second

Sounds like Antony489 could have been on the ball with it idling high to do a regen

 

[phil071]

I used foxwell nt726 (older scanner) then the launch 909E much to my disappointment after being flawless all evening start stop working again its returned to its original state this morning with added problems being milage reading flashing and passenger side door window and mirror not working gone through everything again dpf regeneration etc etc but is not going away no dtcs nothing soot content at 56% sent the diagnostic report to myself I'll try to upload it seriously scratching my head now

 

[phil071]

Sorry soot content from 76% down to 56% after regeneration......

 

[phil071]

Screen shots of report