vrracing

iTrader: (1)

The car has been running well but suddenly last week it stumbles while accelerating and the AFRs move up to 16 or so while accelerating slowly in first and second in a 25mph zone.

The boy drove it home like this which suggests it isnt OMP/MOP limp mode.

As noted in the title the car idles perfectly flat and smooth. This suggests to me that there are no vacuum leaks.

Since it seems to lean out (we have full S5 emissions so unless we are WOT I dont really trust the AFRs at part throttle) Im guessing fuel filter, fuel pump, fuel pump wiring or injectors.

We replaced the fuel pump several months ago. The OEM fuel pump electrical is all in place and unmodified.

I just finished replacing the six year old fuel filter.

If that hasnt fixed it I will:

1. Pull the fuel pump and visually inspect the pickup filter
2. Check for any codes. The CEL was not flashing
3. Check fuel pressure using FSM protocol
4. Check voltage at fuel pump

Am I on the right track? Am I missing anything?

Thank

vrracing

iTrader: (1)

He is in Cali this week and I text'd him and he said above 4000 rpm it runs great and the AFRs are in line. We have a gauge pod on the a-pillar fed by the Zeitronix. We moved the secondary cross-over down to ~3200 via the RTEK2.1.

vrracing

iTrader: (1)

I went ahead and put new NGK OEM plugs in. The ones that were in there were from when we built the engine several years ago, probably 2007.

Here are the old plugs with positions corresponding to how they came out matching their position in the engine. Trailings in back, Leadings in front, front rotor on left, rear rotor on right.