Whenever I start my car it idles @ about 1300 RPM. After it warms up my car idles @ 900-1000 RPM. How can I idle it down? My car is an auto.

 

Stock programming for an A4 is 550rpm in gear, and 650rpm in neutral. At cold start, stock program elevates the idle speed... at 24degF coolant temp , its set to 1,000rpm idle in neutral. Remember, the stock tach typically reads 100-200rpm higher than actual engine speed. You need to put a scanner on it and read the rpm from the PCM.

The idle is controlled by the PCM, using the IAC (idle air control) motor on the base of the throttle body. Again, put a scanner on it, and see what the IAC "count" is at idle. Should be in the range of 20-40 counts, to provide sufficient range to pull the idle down it its too high. If the IAC counts are bottomed out at "0" and the idle is still above the factory program set point, it means either the throttle stop screw is out too far, holding the throttle blades open, or the engine is getting air from some source other than the throttle body.

Have you checked the linkage to make sure the blades are closing fully? Again, a scanner will allow you to read the TPS sensor voltage, and make sure it is within spec at closed throttle (0.20-0.90Volts).

Bottom line... put a scanner on it to check the true idle speed, IAC counts and the TPS voltage. That should point you to the problem.