Juddering on acceleration and difficult to start - SDI

[decvalts]

Had a strange issue that seem to correct itself later on in the day, but would appreciate any suggestions:

Drove up the mountain pass in Glen Shee, car is a bit slow but fairly normal given the incline. Coming down the other side, there's a heavy juddering sensation that I thought was the brakes initially but am fairly sure it came from the engine. (Still judders when clutch depressed and brakes unused etc). Driving along the flat the car really struggles and any kind of acceleration in any gear increases the juddering from the engine. I pull in and switch off, have look at the engine and run the OBD scanner on it. Starting the car next time is really difficult to get started, turns over a lot before engine kicks in properly, then idles roughly. Same problem for a while, carry on down the road hoping to make it to the next big town, but then after a while of very rough running, and very careful driving at around 30-40mph, the noise/judder goes away and power returns...by the time I'm back on the motorway it's cruising along happily again at motorway speed.

There was also a fairly big air bubble in the clear fuel line from the filter when I first stopped and had a look...could it be a one-off bit of air in the system?

Any ideas what this might be? It ran fine all the way home after this issue, but wondered if there's anything that needs looked at before it happens again and I'm not so lucky.

(Fault code was P1161 Manifold Air Temp Sensor open or short to ground. But this goes away after clearing once juddering stops...)

Edited August 9, 2021 by decvalts

[Skezza]

You replaced the fuel filter?

[decvalts]

Yeah - car had a full service including fuel filter just a month ago

[mk2]

If it is the engine... there are a few things you could double check, all of which can cause that behaviour. Air temp sensor (located behind the rhs headlight), the 3rd injector injection timing sensor connection (near the injector) and if the filter was changed, there are 2 little 'O' rings located in the return pressure regulator, pressed into the filter, held in by a butterfly clip. If the 'O' rings haven't been replaced, air can get sucked in, depriving the pump of fuel. The injector pump sucks fuel all the way from the back of the car through a tank strainer and a filter.

It is possible that it could be something else. If it does it again, you can't break anything by disconnecting plugs while it is running- to figure out if it is a particular sensor. No change means you've found it

 

[lupo 1.7sdi]

Replace these two fuel filter valve rings if you didn't when you replaced the filter.

Observe the position of the colors and be careful when changing them to avoid damaging the rings and the valve.

[decvalts]

Thanks @mk2 & @lupo 1.7sdi - I'll have a look at these things. I remember carefully replacing the two O-rings when changing the fuel filter, but I'll double check they've seated correctly and in right order as well. Ta 🙂