S_DosMil

Okay guys. Any expert Chevy mechanics here? I have read over the s10/blazer forums many times over but nothing to help my situation.

i have a 98 Chevy blazer 4.3 vortec. It a code p0507 keeps coming back. I have literally gone through everything.
thanks to a very few generous old auto parts store friends, I have been able to replace the following.

maf sensor
map sensor
ac delco plenum
ac delco distributor
ac delco cap and rotor
ac delco plugs
all gaskets
rebuilt heads
ac delco fuel injection system
ac delco wires
all known visible vacuum lines
pcv valve
brake booster grommet
vaccum T
tps
iac
egr

a bunch other parts which should have no effect on this issue. It runs pretty damn good but at idle it has a stumble which is intermittent. I have spray carb cleaner on every damn part that could cause a vacuum leak and still nothing. Any advice would be appreciated.

S_DosMil

Well found the issue and is not one I wanted. Cyl 6 valve stems or valve seats are bad. It is a pain in the ass to swap the heads again so I will be driving it til it blows up. Also for sale for 600 bucks for someone in California that needs a cheap truck. Can even arrange to handle smog.