4wheel drive 99 expy with a 4.6 . it belongs to my daughter . cats have been gutted , has the same homemade mil's on it that my bird has . it all of a sudden is giving the following after a recent egr valve change ; lean bank 1 and 2 , egr . that's all my son inlaw told me . says it's dumping fuel , you can smell it , idles really erratic / crappy from time to time , seems to be at a loss for power occasionally when you get up to speed . of course it's my fault as i told him how too make the mil's a while ago .......... any idea's guy's ??? i told him to check the o2 sensors to see if they're good and to seafoam the egr passages in the intake etc. my bird runs fine with no cats and the homemade mils , no codes , nothing . maybe the newer obd is more touchy than my 95's ???????

 

That truck has 4 02 sensors,2 on each side. You can run the mils in the rear, but you need the two front 02 sensors (one on each side) to keep the fuel trims in line. Truck will not run right without any 02s in there!

 

phil thanks , we knew that and my bird is the same way . found the problem when they left it here and i began to poke around old school style with a can of starter fluid while it was running { dain surprise too me as the new stuff usually boggles my mind ! } . i found several massive vacuum leaks in that big fitting at the back of the block everything seems to run to / out of . some broken lines , fittings etc. . replaced or repaired 'em and walla it runs right . so my homemade mil's i learned about elsewhere wasn't the issue at all . the issue was too younger guys not used to doing weird old tricks to determine the cause when your stumped .............. thanx again though !!!!!!!!!!!!!

 

Glad ya got er running good.

Yeah,
the vac lines on the back of the motor are known to go bad and cause lean codes.