Rich on bank 2

[Kidd7]

I recently bought an 99 Explorer V6 about 115K miles. I did a tune up because the plugs looked pretty bad. Been driving her mostly around town and no problems. I took it on a trip which I was driving around 80 on the highway for a while. Then when we were back to city speed she bogged down real bad, idled rough and had no power from a stop. If I brought the RPMs up above 2K she ran better, still rough at times. The check engine light would blink then shut off. so I stopped at O'Reilys they pulled a code that said its running rich on bank 2. The guy said Fords don't like vacuum leaks so he would check that first. Any insight? If I never bring her up to highway speeds there is no issue.
Thanks.

 

[SoHK_alumni]

I've never seen a vacuum leak cause a rich condition -- I'd be far more suspicious of the ignition coil, wires or plugs causing a mis-fire resulting in raw fuel going down the exhaust to the 02 sensor.

Could be as simple as one wiring not fully seated on a spark plug or coil terminal.

 

[2000StreetRod]

Misfires?

I've never seen a vacuum leak cause a rich condition -- I'd be far more suspicious of the ignition coil, wires or plugs causing a mis-fire resulting in raw fuel going down the exhaust to the 02 sensor.

Could be as simple as one wiring not fully seated on a spark plug or coil terminal.

I agree. However, often misfire codes are also generated.

Bank 2 is the driver side. You could have leaking fuel injectors in that bank. I suggest adding a bottle of Techron fuel injector cleaner to the fuel tank.

The fuel pressure damper is located on the driver side fuel rail. You might disconnect the vacuum hose and check for fuel due to a leaking diaphragm.