Dick Dastardly Posted March 31, 2012 Report Share Posted March 31, 2012 A plugged Catalytic converter is another potential place to look. Is it factory and how many miles? Just a thought. Link to comment Share on other sites More sharing options...
FAST850R Posted March 31, 2012 Author Report Share Posted March 31, 2012 Something is really wrong for that type of mileage and your driving mostly city. I get 19/20 in town with stop and go traffic. Highway should be 24-28. As mentioned, I would check the coolant temp sensor. Plug in a scanner and see what the computer is reading. If bad the reading will be low meaning the car is running rich trying to warm up. Check for vacuum leaks and the fuel system is working correctly. Tire pressures and alignment also need to be checked. AG Could you give mroe information about the scanner you talk aobut? My car has no vacuume leak because a mechanic did smoke test 2 times to find vacuum leak before. How can I check whether I have a bad fuel system? the fuel filter was replaced 2 years(8000 mileas) ago Thank you. A plugged Catalytic converter is another potential place to look. Is it factory and how many miles? Just a thought. Yes it's factory one with 150k miles. Hum....is there any way I can check whether it's plugged or not at home? Thank you. Link to comment Share on other sites More sharing options...
Keaton85 Posted March 31, 2012 Report Share Posted March 31, 2012 Tire pressure! Link to comment Share on other sites More sharing options...
laird Posted March 31, 2012 Report Share Posted March 31, 2012 All high tire pressure will get you is frequent replacement intervals. If you are way low, that's just as bad. Try a new O2 sensor. 150000 miles is out there for longevity. Link to comment Share on other sites More sharing options...
FAST850R Posted April 1, 2012 Author Report Share Posted April 1, 2012 All high tire pressure will get you is frequent replacement intervals. If you are way low, that's just as bad. Try a new O2 sensor. 150000 miles is out there for longevity. O2 sensor was replaced a year ago with Volvo oem one Link to comment Share on other sites More sharing options...
atefitty Posted April 1, 2012 Report Share Posted April 1, 2012 Air filter was replaced with k&n filter 7month ago. I checked it and it looked very clean. Thermostat was replaced 1.5 years ago and temp gauge sits right at 9:00 o'clock position. How can I tell if I have a faulty coolant temp sensor? I do driving in sport mode but drive like a grandmother. The sport mode simply hold gear in high rpm, which is not the case for me. I barely hit 4 or 5000rpm. Like I said no lead foot here. Thank you for the advice. I usually check tire pressure and set them to 32front and 30 rear....the mpg is still low. I haven't checked it a while but when I set it to the correct psi, I still get only 20mpg. Can spark plugs gap cause bad mpg? Thank you For your coolant temp sensor you would have to know what voltage signal its suppose to send to the ECM when hot and what signal its suppose to send when cold and everything in between..I don't know that information..Basically if it has never been changed and your getting crappy mileage, just change it,,,,your car will run better with a new sensor..A bad sensor will usually make the car run rich becasue its telling the cars computer its cold when actually the engine is hot..it needs less fuel when hot...more fuel when cold. Link to comment Share on other sites More sharing options...
aggarcia Posted April 1, 2012 Report Share Posted April 1, 2012 I have a generic scanner that has the live data option. You connect to the obd port, enter diagnostics mode and select the live data options. You can see every sensor it can see or just selection what readings you want to see. I have connected to the three cars we have. What is available in live data varies by what's on the car. I was using the scanner to find a boost issue. You can see The various sensors and help determine what is not with proper range. If the temp sensor does not ever get to ~200 degrees you are still in warmup mode. You can watch your 02 sensor move through its range to see if it is functioning correctly. It is a great troubleshooting tool. AG Link to comment Share on other sites More sharing options...
BlackBrick Posted April 1, 2012 Report Share Posted April 1, 2012 Is there a way you could test a few days ONLY city driving, and then ONLY highway driving? Would that help pinpoint a few ideas if only one was poor? A slightly higher tire pressure can add about 1-2 mpg, but that's about it. I think 30psi is way too low for the weight of these cars. I tried running them that low once, and saw wear on the outer edges of the tires. At 34-36, I seem to get the best wear, and the steering response seems better. Link to comment Share on other sites More sharing options...
Keaton85 Posted April 1, 2012 Report Share Posted April 1, 2012 Same here, I would wear the outer edge out with that kind of pressure. With higher pressure I can get perfect tread wear although a little rougher ride. Link to comment Share on other sites More sharing options...
FAST850R Posted April 2, 2012 Author Report Share Posted April 2, 2012 Thank you for all the advice and seuggestions. It's been a while I have tried to find the source of bad mpg. I think I will goahed and order temp sensor. It's cheap and easy to replace. I usually don't throw money on things without making sure, but I can't really find the source. Actually, my car runs rich because I can smell very strong exhaus smell when cold start. I mean very very strong. Wish me luck!! Link to comment Share on other sites More sharing options...
FAST850R Posted April 2, 2012 Author Report Share Posted April 2, 2012 Um....OEM sensor is around $60........way more expensive than I expected... Is after market one ok from FCP? Anyone has any experiences with the after market one? thank you, Link to comment Share on other sites More sharing options...
fasteddyT5 Posted April 2, 2012 Report Share Posted April 2, 2012 I have been putting only premium gas since I have owned it. I drive it till I see the low fuel warning light, then I put 10 gallons of fuel. I drive it till I get the light again, and calculate it. The reason I install k&n filter was the bad mileage that I had with oem filter. I thought k&n filter would improve mpg, but I was wrong. If I can get that kin of mile from my baby, I will be very happy. At least in my '98 S70, the fuel light comes on when the car estimates that you have 50 miles of gas left in the tank, based on your recent driving conditions. I do not believe that it is a measure of the volume of fuel left, only how many miles the car estimates you can drive on what's left. If your 850 gas light works the same as the S70's this should not be a very accurate way of measuring MPG. When the light comes on will depend on how you are driving as your tank gets low. The most accurate method is to keep track of how much fuel you put in at the pump and how many miles you drive over several cycles. The bigger the sample the better. Link to comment Share on other sites More sharing options...
FAST850R Posted April 2, 2012 Author Report Share Posted April 2, 2012 At least in my '98 S70, the fuel light comes on when the car estimates that you have 50 miles of gas left in the tank, based on your recent driving conditions. I do not believe that it is a measure of the volume of fuel left, only how many miles the car estimates you can drive on what's left. If your 850 gas light works the same as the S70's this should not be a very accurate way of measuring MPG. When the light comes on will depend on how you are driving as your tank gets low. The most accurate method is to keep track of how much fuel you put in at the pump and how many miles you drive over several cycles. The bigger the sample the better. Thank you for the tips. I guess I will follow the method you mentioned. How about the trip meter? How accurate is it? I get 13mpg in the city driving, and 18.7~19mpg only highway driving without WOT. Link to comment Share on other sites More sharing options...
aggarcia Posted April 2, 2012 Report Share Posted April 2, 2012 That's bad gas mileage. EPA rated the car at 17 city, 24 hwy and 19 mixed. Now with the ARD Blue and 18T, I am getting 20-21 combined. No long highway trips, but the 15g and Stage 1 tune 23-25 mpg on highway trips at 75-80 mph. Somethings wrong. AG Link to comment Share on other sites More sharing options...
atefitty Posted April 3, 2012 Report Share Posted April 3, 2012 Could you give mroe information about the scanner you talk aobut? My car has no vacuume leak because a mechanic did smoke test 2 times to find vacuum leak before. How can I check whether I have a bad fuel system? the fuel filter was replaced 2 years(8000 mileas) ago Thank you. Yes it's factory one with 150k miles. Hum....is there any way I can check whether it's plugged or not at home? Thank you. My opinion is if your cat was plugged you would have performance problems..the car would not accelerate well..it would bog down under load..the engine must be able to breathe to operate normally. Link to comment Share on other sites More sharing options...
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