1999 V70 XC Terrible MPG & Smokey

Digital8 · Post by **Digital8** » 27 Feb 2011, 20:10

1999 V70 XC AWD
132,000
Portland, OR

Looking for some advice. I've owned this v70 for about 2 months and I am only getting 10 to 11 miles per gallon through the whole tank. I use premium gas and only do city driving. Most of my trips are under 3 miles.

I've been attempting to resovle both poor MPG and the Smokeyness through maintenance, but only the smokiness is getting better,and it is not resolved. I have replaced the plugs, oil change+ filter, new K&N filter with only a tiny improvement to the MPG. I just had the PCV serviced and the dipstick has stopped smoking but the exhaust smoke is white and fluffy after the car warms up at times. Not nearly as bad as prior PCV, but still very noticeable. PCV had no impact on the MPG.

The check engine light is NOT on and it feels like it is running great (no misfires from what I can tell). But it has always been this way since I have owned it, so I don't have anything to compare it against. I passed emissions with puffs of white smoke billowing out. My questions are:

1) This is way low, right? I should be expecting at lests maybe 17 or so?
2) Any advice on what I should attempt next?
3) If one of the plug or injectors was failing, it would be very noticeble, correct?

I searched and searched and never found my scenario. I appreciate any assistance.

Post by **precopster** » 28 Feb 2011, 04:10

What is your average speed on these 3 mile trips? This is not a good scenario for economy during the winter months as your motor will reach operating temp about one mile before your destination. Also if stuck in traffic for most of the trip I can see why the poor economy.

Is your hot air flap on the air cleaner permanently closed to the cold side?

Is the thermostat allowing full warmup quickly? Try replacing it and the temp sensor beneath it.

Might be time to look at the O2 sensors as they have a bearing on fuel consumption also. Four wire sensors are rated at 120K miles.

Have you been on any long trips? What is your mileage on a good long run?

Does the motor have good compression? The white smoke is indicative of turbo seals that require replacement.

With all the carbon build up of low mileage runs you may be a candidate for a Seafoam treatment to improve compression and remove carbon build-up on rings.

Post by **jblackburn** » 28 Feb 2011, 06:56

Turbo models do not have an air flap; otherwise that would be a good first starting place.

I dunno, it might be completely normal for such short runs - cars run very rich in cold temperatures to warm up the engine and fluids faster. It also depends what kind of city driving you're doing. Here, we have stretches between stoplights that range from 25-45 mph about 2-3 blocks apart. I get about 17 in a FWD only turbo model just crawling around town, not accelerating over 3000 rpm.

My advice would be before figuring that anything is wrong to go for a longer drive once the engine warms up, reset the trip computer MPG display, and see what you're getting.

zhenya · Post by **zhenya** » 28 Feb 2011, 09:09

10-11mpg sounds low, but not impossible under these circumstances. My city driving is mostly trips of 1-2 miles, at least half of them up some very steep hills. In the winter I typically get 14mpg or so under these circumstances. As suggested though, I know things are ok because I get 26.5 with the roof box on long highway trips.

Digital8 · Post by **Digital8** » 28 Feb 2011, 14:49

Thanks all. I will gather some metrics after a long trip. For the 5 mile stretch that I was on a highway previously, the numbers looked very good, I was looking at the every second snapshots from the computer, but it was a quick trip. I was hoping there was some magic "Poor MPG" bullet.

Regarding Turbo seals- how risky is running with bad seals? I thought it could be the turbo causing this, but I am trying to take baby steps so I know what variables change. Is there any way to test if it is the turbo for sure?

1911colt · Post by **1911colt** » 20 Mar 2011, 15:44

Please let me know what you found out, my landlord has the same problem, it's as if the catalytic converter is full of soot, any news would be greatly appreciated...his problem seems to have started after he had a mechanic put in aftermarket o2 sensors?????

Digital8 · Post by **Digital8** » 20 Mar 2011, 19:23

I am also running a can of seafoam through the current tank.

Digital8 · Post by **Digital8** » 20 Mar 2011, 19:34

I typed up a long response but it doesn't look like it posted. In the past two weeks I have drained and refilled the transmission 3 times (it was terrible). Replaced the plugs again with Volvo ones. Replaced all 5 coils. City mpg has improved to 13. Highway is still Under 20.

Note that when I purchased the car the check engine light was on and they replaced the u2 sensor to resolve. No doubt it was the cheapest sensor that they could get their hands on.

I can tell this car is running when it is idling. Are all v70s like that? I've had Subarus that you could barely notice they were on. Or is my engine just in poor shape? NO check engine light.

I sounds like compression, thermostat, O2 are my next steps. I may just wait a while.