Loss Of Power At Less Than ~1500 Revs

[Sergeant Shambles]

Evening,

I'm hoping to get some kind of clarification or help about what might be wrong before I take my car to a garage for repair - I don't want them to bill me for a load of "diagnostic" work.

It's a 2007 Avensis Tourer (estate) 2.2 T180 with the uprated engine (175hp)

I've had the car about 6 months, and kicked out about 15000 miles. A couple of months ago I noticed that I had lost power below about 1500 revs. Whilst I realise that this is a low range anyway and there is little power there at all, it seemed as though the turbo wasn't spooling up. This trouble lasted a couple of journeys, and then seemed to go away - at the time I thought maybe I imagined it, or some how changed my driving style slightly based on the journeys, a few days a go, the same thing occurred and hasn't gone away.

To explain; it used to be that regardless of what revs I was doing, the turbo would spool up and try to boost the engine, the associated noises and slight increases in acceleration at these low revs would indicate this. Recently, this hasn't happened, I have virtually no power at less than 1500 revs, which essentially means that with the 6 speed box, I can't cruise at 50 mph in 6th gear through motorway road works for example, because the engine can't produce the power needed - this cruising speed and gear hasn't been a problem in the past. It seems that above 1500 revs or there abouts, the turbo kicks in and I get a big boost, that which I would expect from the turbo - so I believe that is is still operational.

There are no extra noises, no knocking, wheezing or squealing when the turbo is on at higher revs, and at low revs there are also no new noises, just nothing. I have noticed an increase in fuel consumption, likely from my having to use lower gears and higher ranges to compensate, so I don't know if this could also be an indicator to a problem. I have also checked the exhaust for excess black smoke, and there is none. I mean to say the exhaust is clear on start up, idle and under load when the accelerator is pressed, I've not been able to check this whilst driving on the road however because of the obvious problems of watching for exhaust gases whilst driving.

I imagine that it might be something to do with the turbo, or it's sensors, but I am not a mechanic and have only a limited practical knowledge of turbo diesel systems so I may also be way off mark.

Any kind of help or feedback would be greatly appreciated. I'll also try to get any more information that's needed.

Thanks in advance.

The Sergeant.