I've had a 2000 volvo v70 turbo @95k for about a year and I've always put 87 octane in it. Volvo recommends 91 in their turbo engines, but consensus seems to be that they run fine on 87. I wanted to see if I'd get better mileage on higher octane so I put 89 in it.

After the first tank of 89, my average mileage dropped to 19 from about 21 or so. Bike rack on the roof complicates the mileage issue, so I wrote it off as having driven more with bikes on the roof.

On the second tank of 89, the CEL lit up. It went off and on a couple of times, but mileage went back up to 22 after that tank, and seems to be heading that way most of the way through the third tank of 89 right now.

checked the code: p1171 and p1174. googling up some volvo forums shows this is either fuel trim lean or MAF/vacuum leak/something else. Volvo MAF sensors are notorious. Also from the forums it seems that volvo dealerships try to solve this by replacing O2 sensors and then the MAF. Inspection's due in a month.

-is it likely that switching gas grades affected the fuel trims and this will go away after a few more tanks?
-how risky is the spray-the-sensor-with-cleaner method?
-is there anywhere I can go to get the MAF output read without paying a dealer $90?

8/22/2008 11:10:51 AM

1. yes
2. clean it with denatured alcohol and water with a lint free cloth (assuming it's a common maf)
3. use a multimeter for $5 at harbor freight, though you probably won't get real meaningful data without a datalogger and baseline.

8/22/2008 1:39:05 PM

you can use spray to clean the sensor.. but i wouldnt use anything except CRC MAF cleaner (not throttle body cleaner, not carb cleaner)

did you happen to let the tank get lower than usual before filling up the last time? when was the last time you changed your fuel filter? could also be a vacuum leak, have you checked you vacuum lines or check valves for cracks?


P1171 - Long Term Fuel Trim (Upper Limit)
P1174 - Long Term Fuel Trim (Upper Limit)
http://www.v70r.com/forums/index.php?showtopic=12254


[Edited on August 22, 2008 at 4:50 PM. Reason : codes]

8/22/2008 4:44:15 PM

have you ever run the thing with premium? i get the best mileage with it.

8/22/2008 8:49:07 PM