Poor mileage and running rich

[fixkick]

we know it is not the engine, with good compression, not head valves leaking. +

The maf goes dirt 99% of the time and goes lean not rich. if factory maf Mitsubishi still there, china mafs who knows, what.

most of these cars set P0171/172 if fuel trim falls off the map (scale)



A good  scan tool can do this too,  shows if the EPA monitors are all run out. means complete, and if complete you get to see all DTC  errors NOW.
that dead cat will DTC 420 wwhen cat montor finishes, but know this,  if the ECU does no like the front 02 sensor it never runs the 420 monitor (hides it)
evap takes ton of driving over 30min to complete, failing man smog tests just for this one fact.



Just to show off what can really be done with OBD2 (1996 and 97 G16 sidekicks both)

here is what my fancy tool can do.
on Laptop, with USB dongle OBD2.
I logged all this data,
the MPG is computed, the ECU never knows this. (from maf readings and speed =vss)
0 MPG not driving. at red stop signals..
note the sweet spot,
so owners of cars only see average MPG, (measured at the gas island pump, odometer read)
this below is reality,  so if you  drive 40mph in top gear 18mpg is 1/2 normal.

note how coasting saves fuel, (fast moving and no fuel to burn cut fuel mode in ECU)