General: 70: mpg-where's it gone

[trojan]

Hi all, Happy chrimbo and all that

I recently had my V70 back from the body shop after a shunt. A week after it was returned I noticed they hadn't changed the Air con rad which had 3 neat holes in it.

When it was returned from that being replaced, I now have ridiculous fuel economy. Prior to the accident I was getting 20-22 mpg on local runs to and from shops, work etc. Even with a heavy right foot I was dropping it to maybe 18-19 mpg.
Now , even with the most economical driving I am getting 16-17 from a full tank and have filled up 3 times since so am sure it is constant.

Upon preliminary inspection I found the large black plastic air channel from the bottom of the air filter box to the fron tpanel was loose and not connected either end. I refitted this and still no decent mpg. Also the engine is very hard to keep revs up when cold.( it has been very cold the last couple of weeks so could this be unrelated)

Could there be sometihng I have missed in the air pipe? Help

Oh yeh its a 2.5 10v 1998 V70

Thanks

[capt jack]

Sounds like something is definitely not back where it should be.

The cold weather shouldn't affect the car's ability to start and run smoothly - it's a Volvo - born in the land of permafrost!

At a guess, the engine management system is getting duff information about the air intake.

Depending upon the exact type of engine management system fitted to the car there will be a couple of key sensors, and quite possibly one or more has been damaged, or not re-fitted correctly.

The Haynes manual describes where each sensor is, and what it does for each of the most common systems, the Bosch Jetronic, Motronic, ME7 and Fenix systems. The most likely for your car is the Fenix system.

If you're minded to have a bit of a delve yourself, then a Haynes (bought from Halfords or borrowed from the Library) is essential. Hopefully it's just a matter of a loose connection etc.

If not, then a return to the bodyshop is needed, although on their past performance I'd be tempted not to trust them with this! The other alternative is a Volvo dealer or independent specialist.

Cheers

Jack

[trojan]

I've got the Haynes book of Truths so I might have a delve myself, as I have no confidence in the bodyshop doing it. I did see a moveable flap on the air box end of the black plastic pipe. Would this be a cause?

I think I'll call the bodyshop next week and see if they will pay for me to go back to dealer as its defo not right.

[ShadeTek]

The garage would have likely disconnected the battery during it's repair making the ECU remap the engine which will make it a bit lumpy for a few runs. If it did this with the pipe off, then try disconnecting the battery again and let it remap with the hose connected this time.

[trojan]

When you say Lumpy, the engine tries to cut out when first started when cold. When I'm demisting I need to keep blipping the throttle as when it drops too low it cuts out. It will idle at about 5-600 rpm and then when warm no problem, apart from drinking too much unleaded.

[cookie]

is Maf connected, really need codes read, possibly a vac leak, or possibly Maf Damaged

[trojan]

I'll read codes Sunday and see what it says. Thanks for the help so far!

[volvo-express]

Make sure that the idle control valve is plugged in and in good working order, ie free movement, this helps to maintain the RMP when cold.

[jeh]

Hi Had the same problem when mine came back from the garage 16+ MPG
check it`s not in sports mode

John

[trojan]

@ john : it's manual so it doesn't have sports mode. Thanks anyway.
@ Volvo express : where's the idle control valve?