2.0. Hdi no low down oomph.

[PeterN]

One of my estates is having a fit of the vapours, over the last few weeks the low speed performance has been declining, it feels gutless at below 2000 rpm but at 2500 it suddenly takes off. It feels very much like a duff MAF but it isn't, I've changed it for a known good one and its made no difference, I also found the throttle cable was slack, I have now tightened it - still no different. No smoke and I have tried an Italian tune up, still the same.

Any suggestions?

Thanks Peter.

[Doggy]

I've heard of this before, but assuming it's not the usual MAF/ air filter issues, I can only think of two possibilities:
A boost leak, (unlikely)
An induction air leak that lets air bypass the MAF

Any other ideas, people?

[PeterN]

Didn't notice anything but will have another look. MAF is OK, all resistances read the same as the original one which has also been tested in my other car. Feels as though it could be pressure loss on the turbo output side but if its that bad you can usually hear it.

Thanks

Peter

[Doggy]

Not sure the resistance will tell you much, I think it's a hot wire anemometer and they degrade over time/miles or both.
One that's not working well typically shows excess air flow at idle and little increase with engine speed, (I've seen at least one where the apparent air flow is lower at 1000-1200 RPM than at idle), hence the ecu doesn't inject enough fuel until further up the rev range.

I'm guessing an air leak between the MAF and the turbo would give a similar result.

[PeterN]

I will try the one I have taken out in the other car, the readings between the others were very similar but change with the temperature, particularly the thermistor of course. I'm pretty sure its OK as I had it in the other car and it went fine. I have found though that a MAF fault only normally affects the performance at below 2000 rpm this is very feeble up to about 2500 then climbs to 3000 very rapidly. I will keep looking.

Peter

[stevewalsh]

EGR Stuck open ?
Try blanking it off

[Doggy]

^ Could be. Definitely worth checking.

[PeterN]

Never had an EGR problem in all the years I have been driving diesels so don't know the symptoms but I will give it a try.

Peter

[stevewalsh]

I made my blanking plate from a sheet of aluminium, using a gasket for a template, never been a bit of trouble since.