Fiat engine problem

I bought a fiat combo van which was 2 ½ years old. It is a 1,3 diesel 95 hp. It starts and runs fine until you reach 40 to 60 mph when the engine starts to judder. It seems to be a combustion issue, a bad mix of diesel and air. It is worse in colder weather. It lasts for about 20 to 30 minutes then it runs better when the engine has fully warmed up. The judder only seems to happen in 4th or 5th gear between 40 and 70 mph.

I have been to five garages to find the answer. The first said it was dirty injectors and made me run the tank to near empty and add a container of cleaner into the diesel tank and run it to almost empty and then fill up. NO DIFFERENCE. Tired this a second time. NO DIFFERENCE.

Next they told me that their computer said the engine needed a software update and that I had to go to Fiat. I did that and the fiat garage did the update and said that was the cause of the problem and that it would be solved. NO DIFFERENCE .

Next garage said it would be a blocked diesel filter so they changed that. NO DIFFERENCE.

And so, several hundred pounds later I still have the same problem. When I bought the van it had been almost unused for a few months because of lockdowns. Might this be part of the issue ?


Please help if you have an answer. Thankyou.

Get a garage to look at live data and as it seems to run ok when hot i would be looking at coolant temp sensor readings to start with.

It's a Fiat engine.
Be glad it starts...

Could be a timing sensor, or a stretched chain

How many miles has it done? Service history? Air filter change?