V70: Engine Plummeting fuel consumption

[Zedster]

Have owned my V70 D3 for around 7 months now. When I first bought it I was over the moon as week in week out it was turning in around 46mpg. Around 3 months ago fuel consumption started to gradually drop and at the same time the acceleration deteriorated, finally two weeks ago the acceleration and power dropped so much that getting up hills was difficult. RAC man was called out and he found a split turbo intercooler pipe between the intercooler and the air intake which he taped up temporarily to enable me to get to a garage. New pipe was purchased from Volvo at a wopping £180 and fitted at a local garage, performance of car deteriorated really badly, with little to no power and surges on accelerating such that the car was kangeroo jumping. Garage wanted nothing to do with it claiming "they had fitted the pipe correctly all it was was two clips, couldn't be due to them". Then I remembered I had a friend with a two poster and smoke machine so we collectively investigated and found smoke billowing out of the connection between the bottom of the hose and the intercooler, after an investigation we discovered the garage had fitted the hose with half the jubilee clip off the hose (it was on a slant). We refitted it ourselves, smoke tested again and it was fine.

The car now drives and accelerates fine but my average fuel consumption is now only 28mpg which I can't live with.

Is anything that has happened above likely to have caused such a drop in consumption? Car is D3 with 128k. Any other thoughts?

I have ran a diagnostic check with VIDA and I get ECM P004900 turbocharger/supercharger overspeed (with low frequency). Under the "unselected CSC" tab.

Under the initial state tab I get:

ECM P140700 EGR no flow detected - low frequency
ECM P004900 turbocharger/supercharger overspeed
ECM P023600 turbocarger/supercharger boost sensor A circuit range.

[Cloth Ears]

I can only be of limited help, but I had very similar issues with my Audi A2 a few years ago. Deteriorating fuel consumption which the dealer couldn't track down. In my case the turbo blew a few weeks later and after the replacement had been fitted, a whooshing sound (and poor fuel economy) led to discovering a split intercooler hose. My supposition is that the split hose led to a turbo overspeed which, in my case, blew the turbo.

So while I can't help with your problem, I can only advise that you tread very carefully until this is tracked down. Clearly you'll not be going back to the garage that fitted the hose so badly in the first place, but I'd suggest either a Volvo or a turbo specialist take a proper look.

[Tatsfield]

The heading is misleading. I got very interested when I read the heading! We'd all like plummeting fuel consumption. From the post it looks more like rising fuel consumption!

[apersson850]

I had a leakage on the pipe under the engine, from turbo to intercooler.
The older plastic pipe cracked rather frequently, but my car is new enough to have the aluminium pipe from the beginning. Still, there was a hole near one of the mounts, in the weld.
This lead to gradually increasing fuel consumption, especially when towing.
Eventually, in a steep uphill with caravan behind, the ECU considered the combination of charge pressure and airflow to be impossible. The airflow was far too high, so there must be a leak.

Had to go to nearest workshop, which confirmed leak. New pipe and the two hoses at the end (new design, old didn't fit) and back to normal. Now suddenly with a noticeably lower fuel consumption, enough to pay for the repair in two years or so, especially with today's diesel cost.
Consumption fell 10-15%, or from around 7 to 6 l/100 km. So it's well worth to make sure you have no air leaks in this region.

[Simmy]

clear all codes then re scan read current faults in the delivery tab

[yostumpy]

suggest, (if not already done so) to clear the mpg readout, and start again now the pipe is fixed. If you let it run on (ie not clearing it every fill up) and you had a split hose, then it will take a wee while for the mpg to adjust back to normal, and will show low figures for a while.
If you have already done so, then I cannot help thee.

[apersson850]

The average consumption/range indication will never go "back to normal". The burden of an unusual consumption will be there until you reset it.

It's different with the predicted range on current fuel. That one is based on last 30 km driven.

[BigGreenThing]

Originally Posted by yostumpy

suggest, (if not already done so) to clear the mpg readout, and start again now the pipe is fixed. If you let it run on (ie not clearing it every fill up) and you had a split hose, then it will take a wee while for the mpg to adjust back to normal, and will show low figures for a while.
If you have already done so, then I cannot help thee.

Just a quick question, how might you clear MPG readings on Vida (if there's no error code)? Just want to reset the whole of mine and begin again! :-)

[yostumpy]

Bring up mpg avg on dash, press reset on the lower part of the left stalk, and Bingo, Bob’s your aunties fancy man. No need for Vida. BUT do it when you fill up, and clear it every time you fill up, you get to see if somethings wrong very quickly.

[simboc2004]

My average fuel consumption has dropped to saying 29mpg following a 700 mile round trip towing my caravan (and with roof box on) to France and it has remained at that figure since reverting back to "normal" car. It has also said 290 miles remaining for the last tank of fuel - from full down to 1/4 of a tank! So, about to try reset suggested by Yostumpy - and will try to remember to do that for every refill...
Interestingly, I discovered in that trip above - with temperatures well over 30C for the whole time - a new error message on the dash display: "Shift down due to Heavy Load" that appeared fairly frequently (as well as "Slow down due to high engine temperature" on one occasion). Had never seen either message before, though both made sense - the car seemed quite happy in a higher gear, but I guess the engine management system didn't agree!