drastic increase in mpg (2003 D5)

[rocky]

Having had a few issues that are now fixed, (Oil plug leak \ Turbo pipe cracked), engine power is back to what I am used to.
I am still getting the "engine service required" every day - thankfully with no loss of power.
I havent had the codes read yet but will do so soon.
My biggest problem now is that I am finding that my fuel economy is still way down on what it should be.
The onboard says that I am averaging just under 45 mpg. By my calcualation I have used 90 litres to do 600 miles giving closer to 30mpg. I know the on boards can be a wee bit out but this is fierce. Typically I expect to get 750 miles to a full tank. I have noticed this over a couple of fills now with the diesel coming from the same source as always.

Why does the fuel economy drop when there is an alarm being triggered. I have seen this before but never as bad as that.
I usually average just over 49mpg on the onboard computer. (2003 D5 V70 214K miles) Roughly 750 miles for full tank

Any ideas why my fuel economy would have dropped so much? Any suggestions? I will post up when I get the codes read again. Thanks

[cheshired5]

Why does the fuel economy drop when there is an alarm being triggered. I have seen this before but never as bad as that......

Any ideas why my fuel economy would have dropped so much? Any suggestions? I will post up when I get the codes read again. Thanks

The most obvious reason is that the information required by the ECM for optimal performance and economy is missing somehow. Either as a result of a failed/failing/dirty sensor or all sensors are fine and there's a physical reason for the data anomaly like fuel/air blockage, failing turbo, split intercooler hose etc.
That's why a code read is vital plus obtaining live data in order to narrow things down.

[xco]

Yep i concur.
Intercooler sounds most likely culprit.
Have a smoke input test done on your engine.
I had this done on MY2004 v70 d5 se as similar probs to you and was the intercooler.
£400.00 done all in at excellent indi volvo garage and mpg straight back up to 52mpg on run and 40+around town.

Hope this helps.

[rocky]

Thanks for your replies. One thing I should add is that this happens every morning - alarm comes on before I have driven the length of myself - stopping and starting the engine doesn't clear however when I drive for an hour or so then it will clear with a switch off. The intercooler was changed about 115K - it is as straight at the bottom as when it went in. Wee bit of dampness on it but nothing major....will get the codes read asap. Thanks