Urban Coyote Posted November 9, 2004 Share Posted November 9, 2004 Hi Everyone, The gas mileage on my 1991 Loyale is the pits and I'm running out of ideas as to why and what to do about it. I'm consistantly only getting about 400km to a tank when I'm used to around 550-600km. The engine has been rebuilt, excellent compression, most gas lines have been replaced, exhaust stysem is good and I just had the thermostat replaced this past weekend. I'm still getting poor miles though. Does anyone have any thoughts to where I could look next? I was thinking oxygen, or coolant sensor, but would either of these explain such poor mileage? I don't think my breaks are dragging, if they were what would the symptoms be? It also seems to get considerably worse the colder it gets outside. Thanks! Urban Coyote Quote Link to comment Share on other sites More sharing options...
WJM Posted November 9, 2004 Share Posted November 9, 2004 Replace the Oxygen sensor. That is likely the problem. I replaced the O2 on my RX, previously only getting ~430 km per tank, and after replacing it, I was getting ~610 km per tank ...So, do the O2 first! Quote Link to comment Share on other sites More sharing options...
river2surf Posted November 11, 2004 Share Posted November 11, 2004 I second the O2 sensor. It can easily be tested with a multimeter. Quote Link to comment Share on other sites More sharing options...
edrach Posted November 11, 2004 Share Posted November 11, 2004 What should a good one read versus a bad one? I second the O2 sensor. It can easily be tested with a multimeter. Quote Link to comment Share on other sites More sharing options...
edrach Posted November 11, 2004 Share Posted November 11, 2004 Odd that these posts should appear now that winter approaches. Here in the Seattle area, the gas stations switch over to gasoline with 10% alcohol content. I've noticed a 15% reduction in gas mileage every year in November which goes away again in the Spring. Quote Link to comment Share on other sites More sharing options...
pizzadude Posted November 11, 2004 Share Posted November 11, 2004 3rd vote on oxy sensor, and here they oxeginate our fuel every winter you get horible milege and all kinds of problems with your car. but not this year whoopie! Quote Link to comment Share on other sites More sharing options...
edrach Posted November 12, 2004 Share Posted November 12, 2004 So back to the same question....how do you test the O2 sensor with a multimeter? More specifically, at what reading is it considered bad? The gas mileage on my '91 Legacy has dropped off significantly in the last year and it still runs great...but I'm down to 21 to 22 around town from the 25/26 I used to get. Quote Link to comment Share on other sites More sharing options...
stngllhm Posted November 12, 2004 Share Posted November 12, 2004 i believe the range is 0 to 1 volt but what is more important is how quick the occelations are as the o2 senser gets old the occelations get slower and so the injectors can't meter the fuel as accerate. it has been a long day so don't hold me to anything i say Quote Link to comment Share on other sites More sharing options...
NorthWet Posted November 12, 2004 Share Posted November 12, 2004 i believe the range is 0 to 1 volt but what is more important is how quick the occelations are as the o2 senser gets old the occelations get slower and so the injectors can't meter the fuel as accerate. it has been a long day so don't hold me to anything i say I think the real issue is that a failing EGO sensor probably reports the wrong O2 level (via its output voltage). If the ECU isn't detecting an error, then it probably thinks things are OK: Output voltage varying around 0.5V Someone (rallyruss?) typed about this at length in another thread. I think his main point was that the ECU uses a 5V at microamp-level "health" signal applied to the same wire as the EGO sensor wire. If the output voltage drops to 0V or rises above 1V (towards 5V), then the EGO sensor is truly fubar. And these may be the only situations that the CEL light comes on. So, I think that we could have an EGO sensor that is misreporting the O2 level but not causing an error. (BTW, there was another thread with similar question today, and I asked the question of how bad an EGO sensor could be before it caused a CEL. Hadn't thought through things, hadn't totally remembered about the "health" signal. I don't want to come off as an instant know-it-all. Just slow to remember and think things through. ) Quote Link to comment Share on other sites More sharing options...
river2surf Posted November 12, 2004 Share Posted November 12, 2004 For single wire O2 sensor, put one lead of the meter on the sensor wire, you need to leave the wire connected. The other lead of the meter goes to body ground. The meter should be set to volts and it should fluxiuate rapidly between .40 and .60 volts or there about. If the O2S voltage is stabilixed between .45 and .55v or the voltage fluctuates very slowly between .4 and .6 volts (crosses .5v less than 5 times in 10 seconds), the sensor is probably bad. To test the systems ability to detect a lean mixture condition, you need to remove one of the vacuum hoses connected to the intake manifold and voltage should drop to about .12 v but still fluctuates rapidly. To test if the system can detect a rich mixture, you need a special tool. Anyway, just replaced mine, it went bad in my 89 GL-10. Good luck! Quote Link to comment Share on other sites More sharing options...
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