Engine is running rich?
No code, right
Just fuel rich smell, black exhaust?
On the fuel rail is the Fuel Pressure Regulator(FPR) passenger side front on intake.
It will have the Fuel Return line and a vacuum hose connected.
Engine off
Remove this vacuum line and check it for Fuel or fuel smell.
Inside FPR is a rubber diaphragm if it leaks fuel will be sucked into the intake via vacuum hose and cause Rich mix
159 has a couple of things that set it
key on, engine off self-test, if MAF voltage is greater than 0.7
Engine running self test, MAF voltage is not between .20 and 1.50 volts
All air coming into intake needs to pass thru the MAF sensor, all of it.
So a leak in the larger air tube will cause bad MAF data, or a vacuum leak.
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