2001 V70XC - sharp mpg drop... 14.8 last night

[Volvo S80]

Hi xHeart,

Take a look at injector O-rings they can cause to have fuel leak also allow air in system which destroys the fuel-air mix and cause the car to run poor and use much more fuel.
If you have cold weather and bad O-rings( which are made from rubber) than low temperatures will cause the rubber to shrink much more than on hot weather which allows much more fuel to leak or much more air in the system which you will notice on mpg drop.

[precopster]

Pull the Shraeder valve and attach the pressure tool directly. That way you don't return a good tool.

[draser]

He's running single digits fuel trims (from another post) so air leaks are unlikely, or for sure no major one. From what I can remember, the fuel trim were slightly increasing so ecu was adding some fuel. But for a sudden drop in mpg, perhaps something mechanical.. like dragging brakes... Any wheel getting hot, I mean warmer than others? In this cold it's hard to tell. The other variable not verified is front o2 sensor, no live data available. But how far off can it be, as there are no codes and the drop in mpg is at least 6mpg? I'm running 20 on my car in same cold, down from 22 in summer.

[vtl]

18 mpg in winter, even slightly below. 22..23 in summer.

[xHeart]

He's running single digits fuel trims (from another post) so air leaks are unlikely, or for sure no major one. From what I can remember, the fuel trim were slightly increasing so ecu was adding some fuel. But for a sudden drop in mpg, perhaps something mechanical.. like dragging brakes... Any wheel getting hot, I mean warmer than others? In this cold it's hard to tell. The other variable not verified is front o2 sensor, no live data available. But how far off can it be, as there are no codes and the drop in mpg is at least 6mpg? I'm running 20 on my car in same cold, down from 22 in summer.

I will post the Live data later this week.

Meanwhile, per draser, here is one from 2/28 captured in garage while idling.

[draser]

I can see the front o2 sensor, missed before, being in range of 2% of 1 lambda, so all good there as well. Don't believe there's anything wrong as far as mixture and conbustion of this engine.

[xHeart]

I can see the front o2 sensor, missed before, being in range of 2% of 1 lambda, so all good there as well. Don't believe there's anything wrong as far as mixture and combustion of this engine.

Thank you for filling in draser.

Do I continue with fuel pressure test once I pick up another gauge?

I can pick up fuel smell very easily. I say, there is no fuel odor in our garage, or when the hood is open. However, I am prepared to service all injectors with Volvo o'rings, if it eliminates fuel loss and restores the mpg.

Is there a hose connection of sorts at the tank that may be failing? Looking up the wheel well, the ground wire (item 9) at fuel filler (item 11) has come apart and disintegrated, see this diagram

The weather is in < 40s.

[xHeart]

Another fill of 14.8 gallons after 210.4 miles.
It is what the DIM show - average 14.2 mpg.

An observation:
The _ _, _ mpg Instantaneous display at DIM shows change as it happens.
A start from idle to a drive at 40mph (1500rpm) would show anywhere from 5.x mpg to 53.x mpg -- always low mpg at start.

Several one-mile drives at 40mph at 1500rpm yielded close to 48.x mpg.

[draser]

Can you read your engine temp when you scan the parameters? Also, need to replace the grounding strap at tank filler if it's broken.

[xHeart]

After a 35 minute drive home, some 16 miles on urban streets.
All modules are responsive with no DTC.

VC on VIDA