V6 CDTi Judder/Under-fuelling at Idle

[ukanalyst]

Hi Guys,

Just a quick post to see if anyone has any ideas or has experienced similar ...

For the past couple of weeks my V6 CDti Facelift's been juddering after sitting idle for a few seconds ... it feels like it's under-fuelling and the fuel computer sometimes shows a drop of 0.1 gal/h. After 6/7 seconds it rights itself and then doesn't do it again until you rev the engine and then allow to idle again.

If the car moves ie freewheel down a slight incline it immediately stops and if you rev the engine while stationary it stops but does it again after a few seconds sitting idle and stationary.

Today I had the air con switched on working quite hard and after a 10 minute journey it did it's thing and then switched on the engine management light switching the car to limp mode ... all was fine when I got back in my car for the journey home although I did switch off air con and the car was still juddering at idle.

I'm trying to get my car booked in to a Vauxhall dealership if they ever call me back but fore-warned is fore-armed as they say and wondered if anyone can offer any advice.

Cheers

Dave

[v6diesel]

Is your car a post or pre facelift?

Sounds like a similar problem to the one I have with mine.

[ukanalyst]

It's a post facelift ... I spotted your post earlier but my issue only happens when Idle and it doesn't seem to matter if the engine's cold or up to temp.

Dave

[Big Sig]

I was thinking high pressure fuel pump but it would do it all the time i would think.

[m8internet]

Mine does this, but it is very subtle
Normally feel it when sat in the drivers seat, put your hand on the gearstick and you cen definitely feel the same vibration
However, I have then moved over to the passenger or rear seats and nothing!
I've also popped the hood when it has happened, put my hand on engine cover and can't feel any vibration

I personally think it is a harmonic vibration

My fuel meter on idle usually sits at about 0.1 or 0.2 gal/h
It doesn't change at any time

[Big Sig]

Mines always on 0.2 with AC off, 0.3 with it on and 0.5 in a frosty morning until its warmed up. I also get an exhaust rattle when driving at about 1100rpm.

[ukanalyst]

Mine does this, but it is very subtle
Normally feel it when sat in the drivers seat, put your hand on the gearstick and you cen definitely feel the same vibration
However, I have then moved over to the passenger or rear seats and nothing!
I've also popped the hood when it has happened, put my hand on engine cover and can't feel any vibration

I personally think it is a harmonic vibration

My fuel meter on idle usually sits at about 0.1 or 0.2 gal/h
It doesn't change at any time

No this is definitely new in the past couple of weeks and much more than subtle ... if I had false teeth I'm sure they'd be on the floor! And my instant fuel consumption drops for the duration and then picks up again to a steady 0.2 (if air con off or 0.3 if on) after it's settled down.

[Gsi3.2]

I think the only 'sure fire' way you'll ever know Dave, is to get it plugged in....it could be as simple as wanting the ECU flashed with revised software or the idle RPM raising slightly..if it's more 'sinister' the codes will reveal all.... let us know what they are..

[m8internet]

What about DPF?
If it is indeed fitted, then it may be vibrating on the idle, equally you would see an increase in fuel usage when it activates

[ukanalyst]

Well took my car into Pentagon in Oldham today and the technician seemed like a really decent chap. The fault presented itself immediately which was a relief (as it's intermittent at the moment and actually only seems to present itself when the engine's up to temp) and what was more of a relief was that the fault codes were still stored. The code states that Cylinder 5 is mis-firing ... there was also a code in there relating to the fuel gauge which has been a bit temperamental since I got the car so it's going in for a full day in a couple of weeks for the mis-fire, fuel gauge and handbrake recall

Cheers all for your comments and suggestions.

Dave