General Garage not diagnosing 04 JTD running prolems - help with diagnosis please

[m1chaels]

Out local independent fiat specialist has had the multi 2004JTD sx115 for a couple of days but apparently can not solve the poor running problem so I thought may be I could help them out with a fault finding list.

Symptoms are engine starts and runs but coughs, stutters and is generally slow to rev when the throttle is pressed (but does eventually rev away); even when fully warmed up - this started suddenly a couple of days ago.
Further clue: there is no fault message (and therefore no limp mode).

My list of possible causes - if anyone thinks they sound likely or can be ruled out please let me know:

1) Throttle pot and its connections - connection in passenger footwell
particularly suspect

2) Crankshaft sensor. Would this cause a fault beep?

3) EGR valve

4) MAF sensor - would this cause temporary slow reving?

5) High and low pressure fuel pumps - don't know much more about symptoms for these

6) Fuel and air filter

7) MAP sensor - not sure what/where this is and what symptoms it would cause

8) The electro/vacuum turbo valve that has been discussed a fair bit recently but I didn't really understand.

Thanks for any help

 

[widemouthfrog]

Are you getting much 'pressure' from the exhaust coming out of the tailpipe (i.e. when you put your hand over the exhaust, does it feel like there's much coming out)? Just a thought, but it may be a collapsed silencer or cat. Have you been driving through any deepish snow lately?

Of your suggestions, I would have thought that 2, 4 and maybe 6 are unlikely because you say that the revs do eventually pick up when you floor it. From what I've read, most fuel system faults seem to flag up a fault message.

 

[T14086]

has anyone monitored air rate/fuel pressures?

 

[m1chaels]

Thanks for responses to date.

Just wondering why you asked this, not deep snow but did have the hand brake bind on and had to use lots of revs to move it from the middle of the road including a couple of stalls - could this have damaged something?

Have you been driving through any deepish snow lately?

 

[widemouthfrog]

All related to the exhaust. The Multi isn't blessed with the greatest ground clearance and the exhaust (and catalyser) could have taken a knock, which may in turn create problems with back pressure (hence the questions about checking what's coming out of the tailpipe). Just a thought.

Mondeos (and some others) are known to suffer with the occasional collapsed catalytic convertor, which can manifest itself with symptoms similar to the ones you described. I've not heard of this afflicting a Multipla, but you never know.