Just as the title says. Need help. Re-installed all the emission parts on and car runs and drives fine but for one small hick up. My idle isn't stable. Once the car is warmed up, it idles around 800 but periodically drops to 500 and almost stalls. Driving is normal but if I come to a complete stop it will almost stall or does stall. How can I fix this problem? I replaced all vacuum hoses, set tps over and over. Tried adjusting idle screw via manual. I'm stuck....

 

Are you coming to a complete stop very slowly or rather quickly. If it's quickly then look at the dashpot as a possible solution.

 

s4, s5? n/a, turbo? is the dropping idle only during your coming to a stop, or anytime you are idling? and how many times have you set the TPS? maybe there is a reason you have to keep setting it?

 

sounds like a vac leak. if you take some carb cleaner and just spritz it into the air intake at the front of the car and the idle smooths out, you got a leak.

if you confirm there is a leak start spraying around the vac lines and ports and listen for a change in idle/whistle.