awful mileage at 149K

[ylwgto]

Your valves look great (cool pic too, looks like an alien!).

Ran the tests with my iCarsoft scanner after a 10 min idle warm up.

LTFT Bank 1 = -0.8
LTFT Bank 2 = -3.9
Fuel rail pressure = 381 kPa
Misfire count = 0 on all cylinders live and historically

Interestingly there were some stored DTCs (even with no check engine or message in info center)
P030500 cylinder 5 misfire
P030000 random misfire
P151B68 idle speed control too low

Not sure how old these DTCs were, but I cleared them.

Any other ideas appreciated. Will order Bosch fuel pressure sensor today.

[ylwgto]

thanks matthew.

will add some seafoam to gas...can't hurt. just changed oil, so donlt want to add any to crankcase now and may not ever due to the higher mileage. also reluctant to do the intake method, since the car is port injection I don't see any benefit now after seeing Paul's valves.

Yes, I drive the car pretty hard at times, especially when driving up to CA mountains.

[matthew1]

Yes, I drive the car pretty hard at times, especially when driving up to CA mountains.

Good man

[ylwgto]

Paul,

You suggested this:

"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)"

Do you mean the
VVT exhaust solenoid for A (i.e. Dorman 916766). 1 per engine
VVT intake solenoid for B (i.e. Ultra Power 916510). 2 per engine

I cannot find any info on a "variable Valve Lift Solenoid "

thanks

[chitownV]

You can click on the codes in VIDA to check when the code occurred and how often. If the VVT is throwing off, it should store a code because of the cam sensors.

Especially at your mileage, I would always first ask what is your maintenance history. Also, what parts & brands you used? These are important as there is a long history of maintenance and certain aftermarket parts that could yield similar issues.
You can go over the real-world maintenance schedule here (it's different than Volvo's service intervals): https://www.swedespeed.com/threads/the- ... st-7332383

As you can tell people are trying to help with two categories, either there is excess drag on the engine/vehicle or you are running less efficiently. It can be more than one maintenance issue, especially if you are approaching 150k miles.

The excess drag can be things like, pulleys, decoupler pulleys, A/C clutch that won't disengage, to dragging brakes, partially stuck parking brake, to old transmission fluid.

Inefficiency can be things like, improper coolant temp control which the engine sees and retards timing, intake runner (flap) solenoids not working properly, the well-known PCV that should be changed between 100k-130k miles, to simple things like the spark plugs or oil in the spark plug holes.

If you can give your maintenance history, it will be much easier to help pinpoint the issue(s). Part of that history is also asking if you consume any oil. On a more rare occasion, you could have pumped bad gas, but that might be alleviated with new gas, changing the fuel filter, and running some fuel system cleaner. I don't like to use the old Seafoam in the tank when there are better fuel system cleaner alternatives out there. You may get worse mileage while burning off Seafoam, thus will have to wait until it's run through and add a fresh tank of gas to reassess your mpg.

Just remember, wide open throttle (WOT) is usually a fixed programmed fuel/ignition map, thus if you are constantly WOT, it may feel like power didn't drop, whereas in everything else, different rpms/loads/temps besides at WOT the computer has made adjustments.

[ylwgto]

Appreciate the detailed reply.

I'm pasting my maintenance history (parts and mileage changed) since I've owned the car, beginning at 119,000m, below.

I've done all required maintenance and nearly all proactive fixes to mitigate potential issues. It is recently that the fuel MPG has tanked, so I feel it has something to do with the fuel system (sensors etc) or maybe the timing sensors?? Not sure what else, could be the culprit. I burn a little oil, about 1/4q every 5K miles, but nothing excessive.

PCV, brakes, tranny fluid, accesory belt, fule filter, plugs, thermostat have all been replaced. I use only OEM quality parts from IPD or FCP etc. I have not changed the coils, injectors or any fuel/timing sensors. I do not have access to VIDA, just a normal code reader.

Any other ideas would be much appreciated!

part changed mileage
oil change (Synthetic) 120000
oil filter change 120000
coil spring insulator 121000
strut mount plate bearing front 121000
Bilstein B4 front struts 121000
Strut bellow, front 121000
strut mount front 121000
4 wheel allignment 121753
Nakamoto drilled rotors/pads (F and R) 122000
Transmission fluid drain/fill #1 (3309) 122000
TPMS sensors - 4 123000
engine torque rod, poly 123000
engine torque mount, upper 123000
Valeo AC compressor 126000
oil change (Synthetic) 126000
oil filter change 126000
Denso iridium spark plugs 130000
Transmission fluid drain/fill #2 (3309) 132000
oil change (Synthetic) 132000
oil filter change 132000
PCV/oil trap engine replacement 133000
evap purge control valve 134000
engine cooler oil hose 134000
engine thermostat 134000
Niokian Zline AS tires 137446
oil change (Synthetic) 139000
oil filter change 139000
Front engine mount replacement 140105
Drifeshaft (prop shaft) 140105
engine air filter 144960
drive belt tensioner 145080
drive belt idler pulley 145080
drive belt 145080
vacuum pump gasket kit 145080
water pump/coupler 145080
Transmission fluid drain/fill #3 (3309) 147300
oil change (Synthetic) 147300
oil filter change 147300
front lower control arms 148100
front ball joint 148100
front sway bar end link 148100
allignment 148100
fuel filter 148100
Techron in tank 148200

[chitownV]

That’s good info, but I don’t see the parts brands. These are just as important. OEM manufacturers might produce specific factory parts, but will make or outsource other parts in their catalogue that have poor quality.

I also don’t see the decoupler mentioned. Do a check by seeing if the serpentine spins one way and not the other with the engine off (normal).

I don’t consume oil in 5k miles and I have more miles than you. That oil has to go somewhere.

Since you don’t have VIDA, you’ll have to get your hands dirty to try to diagnose.
- Remove the spark plugs and read them, keep them in order. Also inspect the coils and boots.
- Drive while observing the actual coolant temp, timing advance, LTFT, and fuel pressure at the same time.
- Double check your work, such as seeing if any PCV bolts loosened up or a loose intake boot.
- Raise one rear wheel at a time to ensure there isn’t any drag from the parking brake or calipers.
- Take pics or look underneath to ensure the exhaust didn’t some how get bent
- Remember that if you clear the codes, it could take several hundred miles and multiple cold starts to reset the LTFT.

From the way you described how the power seems the same as before, there isn’t a starting issue, no other smells or noises, it sounds like the engine module is adjusting to something going awry or there’s some added drag. It doesn’t sound like a fuel issue as that normally should throw a code or cause a running/starting issue, especially with the drop in MPGs you are mentioning.

It might be a good time to get VIDA sorted out. You could spend more money on throwing parts at it. Buying a dedicated cheap laptop from Walmart and the Dice unit could save you money and help in a proper diagnosis.

[xHeart]

I've done all required maintenance and nearly all proactive fixes to mitigate potential issues. It is recently that the fuel MPG has tanked, so I feel it has something to do with the fuel system (sensors etc) or maybe the timing sensors?? Not sure what else, could be the culprit. I burn a little oil, about 1/4q every 5K miles, but nothing excessive.

You have indeed done all critical and preventive care on your car. Same here; this is a quick scan of tasks that I have competed. search.php?keywords=%2B2013A+%2BXC90&te ... mit=Search

Unless you know otherwise, the 13-14 mpg in the city driving is normal on the 3.2 XC90.
If you have VIDA then long-term fuel trim data will verify your assumptions.
Else, there is a massive flow of fresh air; throttle body stuck open; or Put a Tiger in your Tank. Lol!
Are you reading mPG on dash, if so, what are various instantaneous readings - high and low?

[ylwgto]

Appreciate the reply.

LTFT from my scanner (not VIDA) is:
LTFT Bank 1 = -0.8
LTFT Bank 2 = -3.9

STFT seems to bounce all over the place in real-time data stream.

Admittedly, I do not understand what these values should be ( I do know LTFT is close to zero when things are ok, right?)

Instantaneous MPG from dash message center is 8-11 (city) and 14-16 (Hwy) with MPG avg being 13.1 on last tank.

Yes, I've come to expect 14 around town but 8-11 is brutal...worse than my '66 GTO (speaking of Tigers....)

I have not had time to thoroughly check intake system for air leaks, but 2 things of note:

-2 of the 4 screw holes for holding the air cleaner box lid on are stripped, so only 2 screws holding it tight (do not think this would cause any issue)
-when I cleaned the MAF, the sensor housing was loose in the intake tube. I tightened it, but the o-ring is old. Any concern here?

Should I do a battery disconnect/reset to clear the LTFT (i.e in link below)?:
https://www.matthewsvolvosite.com/impor ... trim-ltft/

[chitownV]

If you cleared the codes, the LTFT will need time to readjust again. Check it again daily and you will notice it changes. This is directly connected to the data needed for the emissions readiness and the catalytic converter won’t be ready until the LTFT is set.

I personally don’t like cleaning old MAF sensors, especially if there wasn’t a MAF code to begin with. If you change the MAF, use the same brand. IIRC it’s Denso. Before, I found it was not listed at FCP for the XC90 3.2, but it’s listed if you search under a different Volvo 3.2 model of the same year. It sounds like you need to find a used air filter lid and box to replace yours.

Again, you need more info and find the brands. If you already have 10k-20k miles on replaced parts, don’t assume they are good….verify they are good. You need to read the other sensors and data while driving. You need to read the spark plugs. This would be easier if you had VIDA.

What brand PCV did you use? Was it a FoMoCo/Land Rover/Volvo OE? We have heard of cheaper aftermarket brand PCVs, even OEM ones, that still had issues.

Too many people don’t get data for proper diagnosis. Don’t know why, but they would rather spend a lot more money on parts with assumptions.

You know the MPGs dropped, it still feels like it runs fine, the idle fuel pressure seems fine, and one bank is moderately off of the other in the LTFT. You need to reassess after getting your hands dirty and getting more data since you don’t have VIDA.

What you should be looking for
Remember, you are not dealing with a fuel issue. You are dealing with an issue where more fuel is being used for a given rpm and load. Why more fuel is being requested you don’t know why.

It could be basic like it’s related to air, but where? Could be a simple air leak such as, the intake noise resonator attached to the tube, loose clamp at the throttle body, PCV & vacuum, exhaust leak so it’s reading leaner thus adding fuel, the MAP sensor, the MAF sensor, intake flaps not moving properly (VIDA can activate these for checking), etc.

It could be a maintenance or wear item, like the spark plugs got oil soaked or fouled up, the decoupler pulley dragging the serpentine, a coolant temp sensor reading off, improper A/C compressor alignment somehow not disengaging the clutch, etc.

Remember that actual coolant temp can vary from the dash gauge. The needle in the middle has a wide spread, I’ve seen at least ~20-30F+ in coolant reading change while the needle stayed in the middle. Coolant temp could affect timing, thus less power and more fuel used for a given load in part throttle.

It could be vehicle drag like very very easily checking the rear wheels if the parking brake or rear calipers are dragging. Ironically this happens more often than we would like. Most people never check the parking brake and a realistic thing that happens is a part of the brake shoe breaks off, wedging itself inside the rotor.

When you get more data, when you go over the brands of parts, and when you do some basic checks, this will help focus what the issue(s) could be. I personally wouldn’t want to spend more $ on expensive gas or $$ on parts that are not needed, or $$$ on a repair because I didn’t catch a problem early.