Diesel juddery at 30 in 4th

jk0

I have a 2006 diesel Citroen c5 1.6hdi that has done 31000 miles. Last week it went in for its MOT, though that may be coincidental.

Since it came back I notice an occasional judder when doing 30 in 4th gear, rather like if you were trying to drive it on tickover in a high gear. I took it 20 miles at 60 on the motorway yesterday, but that seems to make no difference.

I see from its service history that it has never had a new air filter, so I just ordered one. It couldn't be anything more serious like a variable mass flywheel at such a low mileage, could it?

Retrogamer

Dual mass flywheel can wear out rapidly if the car has only been used to do short journeys where the engine is usually at low revs. It absorbs the vibrations from the engine and engines vibrate more when being laboured.

My last modern diesel had a worn DMF and it was like a bad vibration and shuffling noise at idle revs or low revs.
This one i have just now has been converted to a single mass flywheel but i wouldn't recommend it.

Stigy

40mph in third gear isn't going to be particularly smooth anyway if you put your foot down. However I appreciate this is clearly different from what you're used to. Low mileage cars of this age can be as temperamental as higher mileage variants in terms of how items wear etc. For example brakes can corrode, clutches can fail and cam belts can perish. This is why there are age intervals on items such as cam belts in addition to mileage intervals.

Dual Mass Flywheels are prone to failure, but if it's just a judder coming from the gearbox area (any further info may disprove this), I'd say it's more likely the clutch. If you need to change the clutch, it might make financial sense to do the DMF at the same time, as the majority of the job would be labour charges and it can equate to a costly job.

Don't quote me on this, but I'm sure a lot of clutch kits now come with a DMF due to their relatively short service life? Would an expensive kit, but worth the outlay.

s_b

it could be the fly by wire throttle pedal being worn at that setting causing uneven running more noticeable because you are in a higher gear
a good scan tool should be able to give you live data showing if pedal blips at the revs you were on

loskie

you need to be in 3rd at 30 mph not 4th

warwicktiger

30 MPH seems a bit low in 4th, surely should be in 3rd still?

bigjl

This could be anything.

When were the fuel and air filters last replaced?

With those kind of miles it could just be coked up, car has likely been short tripped which is never a great idea on a complicated turbo diesel.

Changing filters won't hurt but I would consider getting the codes read to see if there are any faults recorded. Not all faults put up a warning light, sometimes an ECU will record pending faults.

bod1467

loskie wrote: »

you need to be in 3rd at 30 mph not 4th

Really? My Golf suggests 4th at 30MPH, depending on loading/acceleration. e.g. tootling along on the flat at 30MPH the display suggests 4th gear. Similarly it suggests 5th in similar conditions when the speed is just over 40MPH.

GwylimT

warwicktiger wrote: »

30 MPH seems a bit low in 4th, surely should be in 3rd still?

Not at all, the particular engine will be at very high revs at 30mph in 3rd gear. My smaller diesel engine suggests 5th at 30mph on the flat, drives lovely in it too.

Retrogamer

When giving it the beans to blow the cobwebs out the engine now and then i'll bring mines up to 70mph in 3rd but i'd never hold it there.

Because i don't have a DMF anymore i can feel the car labouring more as the vibrations are transferred thought the car rather than absorbed by the flywheel. I usually cruise at 30mph in 3rd now.

Strider590

Diesel or not, 30 is too slow for 4th gear..........

Labouring an engine is worse than revving the nuts off it, both for engine wear and fuel economy.