running lean, code 172, and vacuum leak

[IsaacCarlson]

The vacuum leak is in the back of the EGR valve. The valve stem is leaking on the fresh air side. Is this why my mileage is so good? If I replace the EGR valve will my mileage go down? I don't think it is dangerously lean, just enough so the 02 sensor doesn't switch a lot. I remember a thread a while back about unmetered air...guess now I get to experiment.

[IsaacCarlson]

never mind the replacement.....$90! I am not going to be buying a replacement.

[Dr. Jerryrigger]

electrical tape?

[Tygen1]

I'm the Unmettered Air Leak Guy

I eventually got a Wideband and it showed the AFR was still 14.7:1, so it was determined that the PCM believed the engine was running at a lower load that it actually was and therefore was advancing the ignition timing a little. You may be expieriencing the saming thing...

[IsaacCarlson]

So this is good? I might want to turn my timing back to 10-12° instead of 14°?

[Tygen1]

I'd just leave it the same if it's working and you don't detect any issues. You'd only be changing the base timing by moving the distributor, I don't believe it will help by moving the base timing back, you might want to play with the base timing to see it's effect on mpg's....

[IsaacCarlson]

I moved it from 10° to 14° a while back to increase low end torque but I did other mods at the same time so it is hard to tell what I accomplished mpg wise with the timing. I will try turning it back a little and see what happens.