Hi to everyone...im new here and my english is bad

I try to find solution for my problem everywhere(austrian,german,serbian forums) but without success.

I have Fiat Marea Weekend JTD 77 kw 208000km...and this problem:

Car is starting and running (idle at 850) without problems when is not moving, but when im driving (more than 30km/h) and i let it roll then idle speed fall down to 650 for 2-3 sec and then get back again to 850.This happening only when car moving.

Also when i press clutch (during ''rolling process'') then idle speed stay at 850-if not fall down to 650.

I dont know what the problem is...can be MAF sensor? Becouse i changed clutch pedal switch and engine coolant temperatur sensor then oil and oil/air filter, clean the atmospheric pressure sensor but didn't get better.

I hope someone here know what the problem is...becouse i don't want to sell it after i change a lot of stuff and i also like it .

THX

if it's not stalling, it's not a problem, it's a "feature"
for starters, it's not a good idea to be "rolling" (i'm assuming you mean in neutral at while moving). Not only is it dangerous in case of an engine cut out, you lose assisted brakes and power steering, perhaps other functions too, but you also dont save any fuel. the JTD is electronically controlled, so when you lift your foot of the accelerator, the ECU will stop sending injector pulses, you use zero fuel on slowdown, yet you keep all functionality. win win.
if there is a component failing, perhaps a fault code reading could point you in the right direction.

I know is not good or not saving fuel,im driving since 15 years.And i think everyone can drive how they want to, and that is not the problem or question here.

Problem is that Marea didn't do that before and no faultcodes saved(tested with Fiatecuscan,Texa and Examiner).

I read in other forums that engine cut the fuel when u lift ur foot of the accelerator but this never happend before and i have it like 2 years.

Thx anyway

you drive how you want, i wasn't trying to patronise
i'm quite handy in general, but as a mechanic, im quite limited in knowledge/experience, does anyone who knows more than me agree, that this could be a symptom of there being reduced pressure in the common rail? is there a fuel line pressure sensor in, or after, the injector pump?
do you have a recent increase in smoke from the exhaust?

Hehe...sorry ,i didn't mean nothing bad.

My Fiat have one in and one after injektor pump...i don't know which one is fuel line pressure sensor-i know their names only in german .

No increase in smoke from the exhaust, i mean i didn't notice.

Car is working good, no changes from the time when i get it.

Only first my Fiat began to make knocking noices but just between 1500 and 2200, at idle was everything ok.Then i change and clean a lot of stuff and noices disappear and then this problem come.

I have the same problem with my Punto JTD

I change the pressure rail sensor and the problem disappeared but the next day was again equal.

I replace de valve pressure regulator because the old valve as broke inside the high pressure pump and the car remain equal.

Even with the valve broken the car walked normally only had difficulty in start engine.

I agree with Franglais that this does not seem to be a real problem, certainly not enough to sell the car! Although I am also curious as the why the idle speed is different from stationary to rolling.
I assume we are talking about rolling in neutral with the clutch pedal not pressed (coasting)? If so I presume the ECU is simply trying to adjust the engine speed to a set of conditions for which it is not programmed.
Coasting uses more fuel and cause more pollution than "overrun" and once the brakes are used a couple of times the power assist will disappear, possibly at a critical moment.
I do not agree that a person can drive "as they want" if it means increased risk to other road users (including pedestrians) and worsening pollution...........

I don`t talking about rolling in neutral, i talking in rolling and break in secound gear, change to firts and stop in traffic lights for example.

And the other problem is the black smoke increase from exhaust.

this problem is solved when i change pressure rail sensor but in the next day the problem come back again, and I am afraid to buy another sensor and new sensor die again.