05 GT getting 7MPG, smell unburnt fuel, no CEL and all sensors normal. Help?
2005 Ford Mustang GT, 105K miles stock, bought last month. I get 7MPG city, 9MPG highway. Car smells rich, possibly from the driver side exhaust. Here's what I looked at so far:
- Spark plugs and fuel filter changed
- Cleaned MAF sensor - the readings before and after were identical (sits around 4.8/s at idle, increases with revs)
- O2 sensor 1 voltages oscillate normally between 0-0.9, sensor 2 voltages steady around 0.8V
- Tested fuel trim levels, short term hover around +/- 3% at idle, long term hover around -4% (slightly rich, but not sure if this is enough to decimate my MPG)
I then took it to my mechanic and they also said the sensor readings are 100% normal, plugs are firing, etc. He also checked the exhaust and said he couldn't find a leak. He said he can try shots in the dark like fuel injector cleaner, induction cleaner, etc. but says it'll get expensive quickly.
I'm thinking of doing a ghetto smoke test with a vape, but wouldn't a vacuum leak show up on the fuel trim levels? I'm kind of stuck here.