For months now I've been dealing with a rough idle issue on my 2003 A4 with 95000 Km. The car idles normally for the most part but I get this intermittent stutter, especially when in in gear with my foot on the brakes. After getting a Misfire on cylinder #3 I replaced all the plugs, fuel filter and MAF sensor and thing got a little better but I still experience the annoying stutter although less frequently (No codes since the plugs were changes 3 months ago). The car run perfectly fine otherwise with no hesitation at low or high speed. Any ideas? Could it be a vacuum leak?

 

A vacuum leak could cause a rough idle.

I've used a propane torch cylinder aimed at vacuum lines to detect leaks - if the engine suddenly speeds up, you've found it. Other friends have told me they use starting ether instead of propane. Either one should identify a leak.

 

Anyone know where I can find a vacuum diagram?