Z30DT Engine Judder

[ph67]

Here's an interesting one - my Z30DT judders / is lumpy between 1300rpm and 1800rpm in any gear when accelerating, it's quite happy to sit in this rev range whilst cruising. Symptoms are:

• The problem has been there for several years now and hasn't got worse over time.
• The turbo spools up and whistles nicely from 1200rpm like it has always done
• There's no smoke from the exhaust
• DPF re-gens every 350 miles as it always has
• It can still accelerate in the 1300 - 1800 rpm window when the judder occurs but not as well as it should - it's not as though it hesitates or won't rev at all
• When it hits 1800rpm the judder is gone and it takes of up the road like a rocket as normal
• The engine happily revs to 5000rpm without hesitation - so probably not SCV
• Water temperature rises 2-3 degrees if I accelerate in the judder rev range too much
• Fuel consumption always averaged 40mpg
• No error codes stored / no car & spanner light coming on (and the bulb does work)

The judder is irritating, it shouldn't be there and feels as though there's a misfire or as though the timing is off - but I don't think it's these as it would happen across the rest of the rev range.

Anyone have any thoughts as to what this could be?

Thanks.

[BigWilko]

You cahnged the fuel filter. Mine went like that after i used some diesel additive. I didn't know it was that though, so i carried on using it till the filter was so blocked it went into limp mode. For a tenner it's worth a look? Piece of Pi$$ to change too.

[m8internet]

For the symptoms you are experiencing :
What gear are you in when at 1000rpm?
What gear are you in when at 1200rpm (as you hear the turbo activate)?
What gear are you in when at 2000rpm?

For general driving :
What gear do you normally use when driving at 40 mph?

I could probably recreate those same conditions, by being in 6th gear at 1000rpm and at 50 mph (as the turbo is not active)
I would expect the acceleration to be slow up to when the turbo activates, then at 2000rpm a sudden OOMPH
Even passengers have noticed this, and know it is then time to hold on to their seat...

For any acceleration you have to have the revs ideally above 2000rpm, although you can get away with slightly above 1500rpm
Anything below this and it depends on if the turbo was already active, if not then you effectively have to wait about 3 seconds until the EMS receives the response from the sensor that the turbo is fully active

In most cases this means changing down from the higher gear to a lower one, waiting about 3 seconds, then flooring it
In general I tend to swap 6th to 4th most often, then back to 6th

[Celes]

Try unplugging the EGR. I think the Z doesn't go into limp mode if you do that.

[BigWilko]

accelerate in the 1300 - 1800 rpm window

Lots of torque there on the 3.0

[ph67]

In answer to M8's question:

For the symptoms you are experiencing :
What gear are you in when at 1000rpm? - I don't usually keep revs around this point as it's not happy at this engine speed
What gear are you in when at 1200rpm (as you hear the turbo activate)? - I can hear the turbo start to whistle and feel the pick up in any gear at this engine speed - it always begins to pull from this rpm
What gear are you in when at 2000rpm? - Again any gear - I usually cruise in 5th or 6th at a steady 70ish around here though will stay around these revs depending on the speed limit

For general driving :
What gear do you normally use when driving at 40 mph? - 4th gear usually

This is occurring in any gear, more noticeable in the higher gears.

Cruising - I generally use as higher gear as I can and it mostly spends it's time between 1500rpm and 2200rpm for cruising and it is at the 1500rpm mark where mostly the problem is occurring

Acceleration - I usually keep below 2000rpm when cold and up to 3000rpm when warm, using up to 4500rpm for some fun.....

I agree you will create exactly the same symptoms in 5th or 6th at 1000rpm as I'm getting in the 1300 - 1800rpm rev range with gentle acceleration. It feels clear to me that there is a some sort of problem here - any engine should not judder or feel as lumpy as this does, okay, sure it's fine above 1800rpm but an engine should be smooth across the rev range and anyone should expect it to shudder in a high gear at low revs I agree, but not in this rev range.

It's strange it's only a small rev range it does this, if it was a crank/cam sensor, blocked SCV, blocked DPF or even CV joints I'd expect it to occur all the time or not rev to 5000....

[gtr1000]

Try unplugging the EGR. I think the Z doesn't go into limp mode if you do that.

+1. Give it a try .

[LeeU]

I think this could be either fuel filter or EGR, most probably fuel filter, mine has never done this before but it started doing this last week but I know mine needs a service, which it is booked in for this weekend.
If you unplug the EGR I'm pretty certain it will go into Limp mode, I think I tried it at one point. I may be wrong though.

[ben_3.0v6]

Sounds a lot like mine was the other month and all I'd done to resolve it was change the fuel filter, only other thing is could the torque be too much and the clutch is struggling? Then I'd suspect that would have gone kaput by now if it's been happening or a while?!

[ph67]

The fuel flter or EGR both sound a good pointer to me....

GTR1000 - I think I've read somewhere on this site of it going into limp mode or throwing an emissions warning light when the EGR's been blanked off / disconnected - not having done this before is it an easy thing to try? At least if I try this (even temporarily) and the judder goes away I know it's the EGR....

lee_umney / ben_3.0v6 - The fuel filter's been in there since it was last serviced in July last year, have done about 10,000 miles since then, think I should look at this also, the judder problem has been present in this car for several years now and the filter is changed at each service. I did wonder about the clutch also, it's the original and I'm 600 miles short of 80,000 now though as you say it would have failed by now.