ok this is weird after changeing my plugs about 4 months ago i noticed that every once in a while when i come to a stop and am sitting for while the idle will drop to about 300 and then go up again. i have no codes other than a post cat o2 sensor which went out. the MAF has been cleaned, vac lines replaced(no leaks), air filter changed, plugs changed and the wires and coil packs made sure to not causing a misfire or malfuctioning. what could be the problem, i dont have the A/C running or anything. also this just happened as the weather warmed up. BTW its 1996 a4 q 2.8 12v

 

Maybe just an affect of the heat increasing the load on theclutch fan and the engine retarding the timing to compensate for detonation.
If its not throwing any codes don't worry about it too much.

 

I would clean the throttle body.

 

could it also be caused by a clogged EGR valve.

 

id clean it any to be safe but i dont think so

 

My first thought was the MAF, but if that is "known" to be good, check the EGR line, & make sure there are no small vacuum leaks.

It can also be a dirty TB, that can't close all the way affecting idle.

 

thanks guys im thinking it may be the egr or the TB, i havenet had the idle drop latley ( maybe once in the last week compared to every stop) after spraying the rest of my MAF cleaner into the egr line and TB.

 

100 percent sure your throttle body is dirty had exactly the same problem you are describing and it got worse over time cleaned the throttle body last week turned the ignition to on possition waited for the throttle body to re alighn itself started the engine everything now running perfect

 

does the TB align itself even on a 1996 12v. or is this for the newer drive by wire 30v and newer 1.8ts.