[MetroMPG]

That's good advice, Johnny. My car once developed a cracked vac line (my fault - forced the wrong size line over a tee attachment when I installed the cruise control) that was so bad the car went into closed loop running all the time. But it did not throw a code!

Meanwhile, it was running so rich it was leaving black smoke behind and getting 20 mpg (not kidding) according to the ScanGauge.

bbjsw10 - obviously you'd know if it was that bad, but a little leak could be throwing things off.