I am working on a car for driftfc87 which is a S5 N/A 13B. All emissions have been removed including the BAC, VDI, etc. The only things left on the intakes are the TPS, intake air temp sensor, pressure sensor, fuel pressure regulator, and injectors. Everything else has been blocked off.

http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1

The problem is that I'm getting a slight bucking at very low throttle input, like 15% or less maybe. Currently the idle is set at 1000 RPM's, which is still high, but is the only RPM the car will idle at effectively without stuttering. At anything above this 15% throttle the car runs smoothly it seems. At first I was thinking TPS and made sure to adjust it each time I changed the idle settings. Currently it's set at 1k ohms on the short range, and sweeps smoothly to 4.5k ohms. Long range is .4k ohms and sweeps smoothly to 3.8k ohms. The short range checks correctly, but the long range closed throttle ready is slightly out of spec. IIRC though, doesn't the long range control just the OMP? Could this be the cause?

I then decided to check the AFM for proper function. I checked the resistances according to the FSM and the open and closed resistances are correct. The problem I'm seeing though is that it's sweep is so ******* far off it's crazy. It starts at about 300 ohms closed, then when you start pushing the cone part in the resistance start jumping pretty wildly, like 300-800-200-400-600. Then when it's fully closed it's about 90 ohms. It seems like the sweep range is really really off and this could be contributing to the problem I'm having. Any thoughts?

 

Nobody has an idea on this?

 

The afm is normal. A much better way is to find the output wire (Green/Blue) of the afm and monitor it with a digital meter set on volts dc. Voltage starts out high and goes lower the more you move the vane aftwards. Usually one does this at the ECU plug.

Same with the TPS. Set it when the engine is fully HOT. Monitor the output wire, green/red. It should be approx one volt dc at idle and rise in value as the throttle is advanced.

Buck might be a lean condition or the vacuum line to the boost sensor needs a orifice installed in its vacuum line to dampen the input to the boost sensor.

Might be another thing altogether.

 

I always thought that the better way to check these items is with a resistance check, that way you're not depending on battery voltage, good grounds, loads on, etc. etc. I figured the resistance should function the same way as you mention the voltage. It starts out high and decreases as you move the vane inwards. Do you know what terminals/wires you would use to check the voltage of the AFM?

You shouldn't have to set the TPS with the engine hot when the fast idle cam and thermowax have been removed, which they both have been. Nothing will be holding the throttle open. I'll go out and check it using the green/red wire and use a voltage test and see what it does. I'd imagine it's going to do the same thing as the resistance test.

Also, this is a N/A, so it doesn't have a boost sensor, it has a pressure sensor.

 

Idk mines doin the same thing.....motor mounts are shot...could b a problem?