Using too much fuel

[oldgregg]

I don't know what engine designation it is, but a co worker with a '95 Chevy suburban or something like that with a TBI 350 went from using $100/month gas to $240/month!

I put my snap on scanner on Friday it & the vehicle came up with no codes.

The problem reared its ugly head a few weeks ago so he had the plugs, cap & rotor changed out, still bad.

There are no gas leaks, no gas smell & no black smoke coming out of the tailpipe.

Oh yeah, he says the performance hasn't changed as it idles & runs fine.

Anyone have any clues of what I can look for?

Thanks.

[jmd]

Watch what the O2 sensor is doing. Cross counts and general "laziness" of the O2 should be indicative of needing a new O2.

With a scanner, check the TPS; make sure it's reading the right values; same for the MAP sensor. Check tire pressures & wheel / axle bearings for drag.

[oldgregg]

The O2 did seem a bit "slow" & was my 1st thought.
I'm not sure what the crosscount readings should be & as in most O2's I've read, the O2 was bouncing between .4 V& .8 V at idle.

The TPS & MAP were right on.

Thanks for the help.