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Sudden poor fuel economy on road trip 850 1995

posted by  MFreeman on  Wed Mar 30 10:56 CST 2005
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I went on a trip this weekend in my 850 turbo wagon. Halfway to San Diego I filled up with what I suspect to be some pretty poor gas. An hour after filling up, fuel economy goes from 22-25 mpg to 10-13 mpg. Shortly thereafter the CEL comes on. Get to the hotel where the exhaust has a real acrid smell.

In the morning I filled up with premium gas and fuel economy was back to normal and the bad smell disappeared. However, I checked the codes (on vacation no less!) and came up with 4-3-6 and 2-3-1 on A2 and 2-1-3 on A3. I cleared the codes and CEL and spent the next three days with no problems.

Driving home I stopped halfway to get gas again. This time with premium gas and yet again about an hour after filling up mpg goes down to 10-13 again. CEL did not go on again. Get home and get the same codes.

Does anyone have some advice as to the real culprit causing this to happen?

Thanks in advance,

Matt








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    Sudden poor fuel economy on road trip 850 1995

    posted by  burchs1 on  Thu Mar 31 16:20 CST 2005
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    Hi,

    Check all your vacuum elbows..in particular check the elbow on the passenger side of the intake manifold, just to the right of the power steering fluid resevoir. If you have a vacuum leak you will run rich, have poor fuel economy and if you don't fix the problem your O2 sensors will eventually fail. Check here for more details on this:

    http://www.volvospeed.com/Repair/vacuum_lines.htm

    -Scott








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      Sudden poor fuel economy on road trip 850 1995

      posted by  MFreeman on  Thu Mar 31 17:43 CST 2005
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      At first I suspected bad fuel from a not so well kept Mobil station in Yuma, 87 octane. On our return trip again there was a sudden drop in fuel economy after fueling at Chevron in Yuma, 91 octane . We had refueled an hour prior to the fuel economy drop so it is not likely to be the cause. What I do suspect is a failing O2 sensor or some other control device. The drive to San Diego and return trip experience have two things in commom. The sudden drop in fuel economy occured after approximately 300 miles or 4hrs of driving. The vehicle resumes normal operation after sitting and normal city driving. With the fuel economy drop there was not much of a noticable change in performance, perhaps slight loss of power but not much. What components will fail after prolonged highway driving and then recover; O2 sensor, MAF sensor, catalytic converter? Code 436 is for the rear O2 sensor compensation and 231 is a lean or rich condition.

      Thanks,








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    Sudden poor fuel economy on road trip 850 1995

    posted by  someone claiming to be bl on  Wed Mar 30 15:04 CST 2005 [RELATED]

    Another likely possibility is that you have an 02 sensor in the process of failing. Rot gut gas will cause problems right away (you said mpg didn't drop for an hour) and is unlikely to cause such a drastic drop in mpg w/o some other symptoms (notable drop in driveability, surging, rough idle, loss of power). Have you looked up your codes?








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    Sudden poor fuel economy on road trip 850 1995

    posted by  tina on  Wed Mar 30 12:33 CST 2005
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    last visit: Thu Nov 24 09:34 CST 2011
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    I wonder if these places - being along a freeway - figure they can dilute their gas because their customers do not have many choices where to stop and they are not likely to be repeat customers anyway...

    Any way to drain the tank and fill with some known good gas? Maybe change the fuel filter too perhaps it became clogged.







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