So my car won't hold idle anymore. I'm thinking it is a bad fpr but wanted to check before spending another $100+ just to be sure. My wideband is telling me I'm running rich, around 13 but prior when the car used to idle it would be around 15. So now when I start the car it will only stay running with my foot on the gas, again reading around 13, but when I look at my fuel pressure it constantly jumps between 20-25psi with the screw almost fully screwed in. Originally thought it was a vacuum leak but spayed around and nothing. Need to get it running asap.

 

S4 or S5?

 

S5 t2

 

If you were to unplug the AFM and jumper the fuel check connector does the car run differently and does the pressure change?

 

Where is the check connector?
When the afm is unplugged the car definitely stumbles hard. Not sure about the pressure.

The car revs smoothly but doesn't hold idle.

 

It's found near the harness which supplies the boost sensor (usually hidden under the harness). Yellow plug encased in a Black rubber boot featuring two wires (Brown and a Black). You could also have issues w/the fuel resistor relay and wiring back to the pump. At some point in time you might want to hard wire the pump from the battery and see if the pressure is changed.

 

Got it to idle but the fuel pressure is still unknown. It is an aftermarket one. Once I screw it loose, it will be stable around 25-30 psi. Then when I screw it tight it will drop and do the flutter between 20-25psi.
I'm hoping it may just be the gauge, but still not sure if the whole thing is bad

 

if need be you can rent/borrow a pressure gauge from the local auto store.

 

Fuel Filter

 

And maybe your pulsation damper is defective.