My OBD-2 scanner is giving me some far out numbers on fuel trims. This started before I recently replaced my Y-pipe and hasn't changed since. These are the numbers I'm getting:
Short term trims, sensor 1: ranging from -3 to -12 across a range of conditions.
Long term trims, sensor 1: ranging from -3.9 to -5.5.
Short term trims, sensor 2: ranging from -2.3 to -10.
Long term trims, sensor 2: -3.9 to -5.5.
Short term trims, sensor 3: -25 to -30.
Long term trims, sensor 3: -26 to -28.
Short term trims, sensor 4: -24 to -30.
Long term trims, sensor 4: -25 to -26.
My scanner doesn't tell me which sensor is which (i.e. upstream, driver's side), the manual doesn't either. I have a Bluetooth ELM27 OBD-2 dongle on the way I'm going to hook up with Torque Pro to get a more useful readout.
In my research on DiscoWeb and elsewhere I saw mention of other possible culprits, including fuse 3 under the steering column (was fine) and faulty MAF. Here are some data ranges from my scanner during a test drive last night. Again, I don't know what the units are or what range they should take.
- 0.17 - 0.20 at 25mph, 1,000-1,200rpm
- 0.45 - 0.55 at 60mph, 2,400 rpm
If my MAF was faulty, wouldn't that affect the fuel trim on both banks?
Recent work done:
- new Y-pipe and gaskets
- new driver's side upstream O2 sensor (NGK/NTK)
- reconnected loose wiring on car side of same sensor connector plug
Not so recent, but also done:
- new fuel pump
- new fuel pump wiring harness
- new O2 sensors on passenger side
I'll probably get some better data with better tools - my scanner is not the greatest - but until then what are some other things I should be looking for or testing to track down causes of my large fuel trim numbers?