2007 XC90 4.4L using lots more gas now

Paul1963 · Post by **Paul1963** » 10 Mar 2022, 11:02

OK for quite sometime my car is been using more gas than It normally did and as of late it’s gotten really excessive I’m getting like 10 miles to the gallon
I have an Innova 5160 RS2 scanner and My fuel trims look great my map sensor seems to be reading fine my mass airflow sensor seems to be reading fine I have no codes telling me there’s a problem with anything and I recently,.just a week ago Took off the Plenum and replaced the PCV valve, the hose that goes to the manifold and the hose that goes from one valve cover to the other all brand new Volvo parts including Volvo plenum gaskets
years ago the balance shaft was done on this engine and the mechanic made a mess and he never cleaned up the intake Plenum left it all crusty and nasty and I’m not so sure he didn’t reuse the gaskets so now the car runs even better than it ever did it always ran pretty good but it now runs really smooth and beautiful

However its using a lot of gasoline!
Checking it when I fill it, odometer against how much I put in the tank to top it off I’m getting around 10 miles to the gallon as where the car would get 18 around town in about 21 on the highway not long before

It’s crazy how good an engine can run and still have some weird problem and I’m at a point where I’m asking the community now has anyone run into this problem with heavy fuel consumption and what did you find out to be the problem on your V-8 XC90?

I’d really love to have a conversation with someone about this on the phone while I’m in the car,..scanner hooked up doing live data
someone that may know more than me about what sensors should be reading and so on and so forth

Thanks guys
Paul

Post by **RickHaleParker** » 20 Mar 2022, 23:42

Maintenance up to date? Plugs, filters, oil changes .. ect.
When was the last time you cleaned the MAF sensor?
How old are the fuel injectors?
How old are the O2 sensors?
Have you done a glove test?

Paul1963 · Post by **Paul1963** » 23 Mar 2022, 11:59

New plugs,coils are original but no misfires or anything like that just did the PVC system which is the valve the 4 inch hose that goes from it to the manifold the smaller hose that goes about 9 inches from one valve cover to the other and the two Plenum gaskets all the parts I just mentioned are Volvo
Recent oil change with Castrol syn European formula 0W 40 oil
Fuel injectors are original but since doing the PCV job the car runs even smoother than it did before and it always ran very well now it’s incredibly smooth And my fuel trims are excellent as we were before they were a little on the high side but not too much now they’re really really good

Post by **RickHaleParker** » 27 Mar 2022, 22:01

I would start with cleaning the MAF sensor. Use MAF sensor cleaner only.

Post by **shiloh51933** » 28 Mar 2022, 07:14

I'd replace the coils next time you do spark plugs and the fuel injectors are probably fine but you could check the fuel pressure at the rail. Most likely your MPG loss has something to do with your catalyst, regardless of present DTC's. Your MPG's are really low and your concern is understandable.

Post by **RickHaleParker** » 28 Mar 2022, 21:56

shiloh51933 wrote: ↑28 Mar 2022, 07:14Most likely your MPG loss has something to do with your catalyst, regardless of present DTC's. Your MPG's are really low and your concern is understandable.

Tired / contaminated O2 sensors can increase the MPG without tripping and DTCs. Same goes for fuel injectors.

Check the smaller stuff less expensive stuff first like MAF sensors.

Post by **kallekula** » 29 Mar 2022, 05:10

In the past, replacing upstream O2 sensor(s) has increased mpg on my cars. Never had so bad mpg as you though. Thought my bmw was thirsty with it’s 17mpg.

Post by **shiloh51933** » 30 Mar 2022, 06:16

Were not the original owners of our 2008 XC90 V8 but are local city mileage isn't that great either but 10MPG is really low. Were getting about 14MPG local driving, we really haven't driven much hwy mileage yet because I've been sorting things out since we purchased her in December. If you look at the specs for the XC90 V8 model for 2008 Volvo claimed 13mpg city/19mpg hwy. So they don't get great gas mileage to begin with considering the weight of the vehicle and the 4.4l.

Post by **RickHaleParker** » 02 Apr 2022, 22:12

shiloh51933 wrote: ↑30 Mar 2022, 06:16 If you look at the specs for the XC90 V8 model for 2008 Volvo claimed 13mpg city/19mpg hwy. So they don't get great gas mileage to begin with considering the weight of the vehicle and the 4.4l.

They are bricks in the wind.

My 2005 XC90 T6 get 15/20 unless I get on the interstate and push it to 75. Most of the time I stay off the Interstate and run the side roads at 55 - 65.