As the title states, my car is having problems idling. With the maf plugged in it idles around 3K. Without it will idle between 1.5K and 2.2K rpms. I've tried 2 different mafs (N350 and N370), ecu's (N351 and N374 chipped by JAM Performance) and boost sensors. There are no vacuum leaks (I made a vac tester). Tps is in range (I made a tps tester). I don't know why it won't idle correctly. It has a medium street port, rats nest removal, modded TB, stock S5 turbo and 2.5" DP (if that matters at all). I need help!!! Thanks in advance.

 

The fact that the car even runs without the AFM plugged in indicates a serious problem.

Since the throttle body is "modded", first check to make sure that none of the plates are beind held open. There are adjustments for all the linkages.

 

Well I exchanged the throttle body with a stocker, but the coolant ports on the rear iron and water pump have been blocked off. When I changed the TB I used a different TPS. I got it to idle ok but thats with the TPS adjustment screw turned all the way in. I plugged in my tester and only one light is on. If I back off the adjustment the car just misses and tries to die out on me. Any suggestions?

 

Unplug the BAC and that other bypass under the BAC. If this high idle goes away, that means one of the resistor on the ECU is short or open. The Resistance values are 4.2 Ohms, I have encountered a much higher Idle at 4K. Hope this will help!

 

I've had it running with and without the bac. Does anyone know if the S5 N/A BAC is the same as the T2? Any advice on the TPS issue?

 

The NA and TII BAC can be swapped.

Don't use the test light method to set the TPS. Fully warm up the car so that the cold start stuff isn't holding open the throttle and then adjust the TPS with an ohmmeter for 1K.