Posted: Sat Jul 23, 2011 12:22 pm Post subject: Low Gas Mileage
2001 LS with 80k miles.
I am getting worse mileage than usual (~20%), so I hooked up a fancy scanner and got these values.
Ignition Advance (deg): 19.5-22.5
TPS = 0.3 (at idle)
Calc Load % = 1.9
MAF = 3.91-4.2 grams/sec
MAP = 31-32 KPa
Coolant Temp after 5-6 min idling = 192
IAT started at 166, went up to 118, eventually went down to 107 with ambient temp probably around 75 outside
O2S11 ranged between 0.095V to 0.85V, changing every few seconds
Short Term Fuel Trim from -1% to +0.8%
Long Term Fuel Trim always steady at 0.0%
I was worried about the LTFT begin 0 on a 10 year old car, seems like that would not be possible. Also curious about the Intake Air Temp as the car had been sitting for a few hours and it was about 75 degrees outside.
the IAT is probably high if you had the car sitting there at idle while testing. The intake tube and filter housing will soak up engine bay heat causing the IAT to go up.
i might just put a new one in and see because it looks fairly easy and cheap.
What exactly were you using to log. From what I've read, you need to take the fuel trims with a grain of salt unless you are using a full blown scanning tool program.
my friends handheld scanner. it gives "live" values of the measurements i listed
Edit: but it could be lazy 02 sensors, lower intake, or could be something really simple like a fuel filter, or a combo.
I did have to have the cat replaced a couple years back. It was really strange but the car would almost redline the rpm's before changing gears. turned out to be a blocked cat. did get that one done for free due to exhaust warranty.
Overall I am thinking of changing the fuel filter, O2 sensors and the IAT sensor. Will post back when I can finally get to it.
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