I have a 1999 MK3 Jetta and when checked this fault code P0506 came up. My jetta used to stall out when I pushed the clutch in sometimes and when I checked the code it had a P0102 code. I replaced the MAF and the light went out. Now 3 days later the light came on again and it was P0506. The RPMS rev between 400 and 600 when the A/C is on but it idles fine (around 900) when the A/C is off. This car is really pissing me off. Anyone had any problems like this with theirs or anyone know what I need to check. Please help me out I am getting pissed and might drive this piece of shit off of a cliff. Thanks Travis

That code can be difficult to diagnose (Idle lower than expected). Start by cleaning out the throttle valve. I advise doing this on the car as if you disconnect the electrical connector you may have some difficulty restarting.

Does anyone know the steps to clean the throttle valve?

Remove the rubber air intake from the throttle valve & open by ulling the gas pedal linkage. Spray with throttle body cleaner (not carb cleaner) & scrub with a toothbrush. Repeat as necessary. Car will be flooded at restart. You can spray some in as the car is running in order to get some solvent through the idle circuit , but you are likely to set a MAF code. You can remove the entire unit from the throttle body to soakin a solvent bath (be sure the solvent is safe for the electrionic portion), but it may be difficult to restart.

Remove the rubber air intake from the throttle valve & open by ulling the gas pedal linkage. Spray with throttle body cleaner (not carb cleaner) & scrub with a toothbrush. Repeat as necessary. Car will be flooded at restart. You can spray some in as the car is running in order to get some solvent through the idle circuit , but you are likely to set a MAF code. You can remove the entire unit from the throttle body to soak in a solvent bath (be sure the solvent is safe for the electrionic portion), but it may be difficult to restart.