Im asking this for a freind, hes got an FB with a full s4 TII drivetrain, and an SDS stand alone. I dont know everything about the mods, I know its a stock turbo, full exhaust and front mount. MSD fuel pump, MSD 6AL with the boost retard thing. I think a RRFPR. The car put down 245 whp at I think 14psi. Hes got a problem, every once in awhile, (well, quite often actually) the car just falls on its face. It will rip through one gear, and as soon as he hits the next, it wants to die, and his AFR shoots up to around 18. It doesnt knock though. His fuel pressure never drops, his ECU was sent in to SDS and he has paperwork saying its good, he's switched out to the base map and back to his "power" map and back, and changed the O2 sensor, and nothing has fixed it. Like I said, it runs great, starts up just fine, idles good (he says it likes to idle at 1500?) and hauls ***, just freaks out sometimes. I told him to try changing the MAP sensor, maybe coolant temp sensor, and look at the plugs. Any more suggestions?

 

Is he just running the MSD fuel pump?
I'm suprised he made that much power with just that fuel pump!
That MSD fuel pump has LESS capacity than a stock FC turbo fuel pump!!!
Scary!!!

Get a bigger fuel pump (Walbro) and call it a day!


-Ted

 

And - check the sweep of ohms values from the TPS.
It may have a bad spot.

Also test the voltage & connections at the MAP sensor & the fuel pump.

edit: oops - if the fuel pump voltage was bad, you would see the fuel pressure drop.

My best guess is an intermittant sensor or connection.