awful mileage at 149K

[ylwgto]

My otherwise nicely running 2009 Xc90 3.2 has now 148K on the dial. It recently has plummeted to 12mpg around town and 17 at best on the hwy. Awful numbers. Been reading up on the topic and I plan to (in this order):

run some techron with the current tank of gas
clean the MAF
change the fuel filter

any other ideas? i know these cars don't get great mileage, but this is a notable drop off from the already bad 15/19 I am used to.

just changed oil/filter and air filter at 145K and did a trans drain refill. car is running great. plugs were changed at 120K.

Also pondering a seafoam treatment, but read they really only benefit the turbo and direct injection cars. truth?

[volvolugnut]

Proper pressure in all the tires? No brakes very hot after a short drive? E brake partially engaged?
volvolugnut

[ylwgto]

yes, tires are new and properly inflated.
brakes were done at 120k (new pads/rotors) and working perfect with no e-brake drag

car runs and drives great, just a very noticeable drop off in MPG. I've never changed the fuel filter (have it and plan to this week). I know a gumed up filter can screw up engine performance (idle, throttle response etc), but can it impact MPG too?

[ylwgto]

cleaned the MAF. instant improvement in idle quality. the sensor was actually a bit loose on the intake tube (torx screws not tight), so maybe a lack of a good seal there is part of my MPG issue as well?

Also added Techron injector cleaner. We'll see if I can get away from the 12-13 around town mark!

What do you all think of adding Seafoam to tank of gas? If recommended, I'll do that before I change the fuel filter.

[pgill]

My 2008 LR2 3.2 and 2010 S80 3.2 both are capable of getting much higher MPG than what you are getting.

The XC90 is bigger so it won't be quite as good but it should be close

Note: to get good highway fuel economy you will need to keep the RPMs under 2000 (about 64 MPH for my 3.2's)

FREE2 READERS,

The results are in and they are amazing

Note: this is with the cruise control set to about 100 KPH

My LR2 went almost 300 miles

26.9 MPG.

https://www.freel2.com/forum/topic35826.html


Here are the things that I've done to my 3.2 that will affect Fuel Economy

1. Replaced the Thermostat and the Intake Manifold Gaskets https://www.freel2.com/forum/topic32245.html

2. Replaced the Fuel Pressure Sending unit viewtopic.php?t=87687&start=110

3. Clean the MAF

4. Replace the Fuel Vapor Recovery Purge Valve viewtopic.php?p=631482&hilit=purge+valve#p631482

5. Replace the Sparkplugs with Denso Iridium 4704 https://www.freel2.com/forum/topic35121 ... denso+4704

6. Clean/Rebuild the Brake Calipers and Grease the Pins https://www.freel2.com/forum/topic36953 ... =silaramic

7. Replaced the PCV Valve https://www.freel2.com/forum/topic32107.html


Things that I haven't replaced that I would check if my Fuel Economy was bad

A. Intake Variable Valve Timing Solenoid (qty 1)

B. Intake Variable Valve Lift Solenoid (qty 2)


Good Luck

Paul

[ylwgto]

Great info, thanks!
Replaced the fuel filter this weekend...looked original and flow was awful. Driving immediately after the engine seemed to bog down under WOT...like it needed to re-adapt to better fuel delivery. is that possible?

A few q's below about other items. would really just like to get back to the 16/20 I used to have!

**to get good highway fuel economy you will need to keep the RPMs under 2000 (about 64 MPH for my 3.2's)
WILL NEVER HAPPEN, I DRIVE TOO FAST

**Replaced the Thermostat and the Intake Manifold Gaskets
ALREADY DONE

**Replaced the Fuel Pressure Sending unit
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

**Clean the MAF
ALREADY DONE

**Replace the Fuel Vapor Recovery Purge Valve
ALREADY DONE

**Replace the Sparkplugs with Denso Iridium 4704
ALREADY DONE

**Clean/Rebuild the Brake Calipers and Grease the Pins
ALREADY DONE

**Replaced the PCV Valve
ALREADY DONE

**Intake Variable Valve Timing Solenoid (qty 1)
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

**Intake Variable Valve Lift Solenoid (qty 2)
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

[pgill]

Great info, thanks!
..........................................................................................................


**Replaced the Fuel Pressure Sending unit
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

....................................................................................................

**Intake Variable Valve Timing Solenoid (qty 1)
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

**Intake Variable Valve Lift Solenoid (qty 2)
DO THESE NEED CHECKING IF NO ERROR CODE IS PRESENT?

The Check Engine light is there if the ECU cannot maintain emissions.

The light may not be set as quickly as you might expect.

I replaced the Fuel Pressure sending unit on both of my 3.2s prior to 150K (I did get the light but I had the sensor on my shelf just in case, in retrospect I should have just replaced it proactively.)

As for the Variable Valve Timing and Variable Valve lift I haven't replaced either but I have helped others that did need to replace these solenoids.

I do recommend that you make sure that you Oil Anti Drain Valve is working. If it fails it will affect oil pressure and those solenoids rely on oil pressure to work. viewtopic.php?t=92091&start=30



The one thing that LR2 Mike did that I haven't done is to replace all of the Fuel Injectors with refurbished ones.



I would do the following if I were you

1. recognize that you done a lot already

2. replace the Fuel Pressure sending unit (it isn't expensive if you get the BOSCH part)

3. inspect and if it is broken then replace the oil anti drain valve (under the oil filter)

4. post your fuel economy results here


Good Luck

Paul

[ylwgto]

thanks, Paul.

Will R/R the pressure sensor. the bogging down under WOT hints that you may be right about an eminent failure there.

Was also pondering replacing injectors with remanufactured OEM DENSO units for $160, but that is $$. So maybe not.

Is the 3.2 L6 a direct injection engine? Was also thinking of de-carboning treatment like seafoam or the type the indy-mechanics do. money well spent or....?

Appreciate the info, as always.

[pgill]

The 3.2 is intake port injected so it doesn't suffer from the direct injection carbon build up.

If you use quality gasoline then I wouldn't worry about that.

Do a search for Top Tier Gasoline if you want to know more.


Here is one of my intake ports at about 100K Miles

Top Tier Gas only, no cleaning, but I did replace the PCV proactively (before it failed)





Before looking at the injectors I recommend that you check the Long Term Fuel Trim (LTFT) for Bank 1 and Bank 2

I believe that both of mine are under 5%.

If you are higher than that then check it again after you replace the Fuel Pressure Sending unit.

Post what you find here when you get a chance.


If your diagnostic computer will tell you you can also look at the Misfire counts.

My Autel has this information.




Good Luck

Paul

[matthew1]

I would add in 1/3 bottle of seafoam in the next fill up.

Do you hammer the throttle at times? It sounds like you do, so I don't think this is a problem.