LT1 idle issue
 

Ok, so here goes the one problem on my car thats been giving me headaches for about two years now. When I bought the car in 08, the car ran perfect, no problems, then out of nowhere, it developed an idle issue. When I start it, sometimes it will idle fine, other times it will idle real low, and when i go to pull out of the garage, it wants to die...then I stop the car, and the idle will come back up, other times, it will idle real high at first start up (2,000 rpms, or 1500) Other times ill be driving the car and ill throw the clutch in to come to a stop and it will idle at 2,000, then ill come to a complete stop, and sometimes it idles down, sometimes it doesnt. About 2-3 weeks ago, I took the car to the movies, after the movie, I hopped in the car to leave, started it....and it died instantly, started it again, but had to keep my foot into it to keep it running, but ran fine when i was going down the road with my foot into it. Ive replaced the IAC, TPS, IAT ( I replaced this, and it seems to idle low more often( around 500 rpm) but just the other day it was idling high), checked for vacuum leaks (I havent found any) my egr valve isnt stuck open, i can reach behind the intake and push it open, and it runs real rough then dies (as it should) I had this idle issue even with my stock TB, so i dont think its the 52mm, replaced the coolant temp sensor, I havent had any codes lately. A year ago tho the car threw an EGR code, wich I erased and havent seen it since. When the car idles high I can hear a hissing noise but its coming from the k&n filter...almost as if the enigne is trying to suck in to much air. Ive sprayed carb cleaner aroudn the intake, no changes in idle. And then there are those days where she runs absolutely beautiful.

Sorry for the long read.....any help?

I'd say small tear in the intake route or the idle control sensor needs to be cleaned on the tb but that is where i would start

Sounds like a bad map sensor to me. Check the sensor and the oring/gromet. Usually a good starting point.

I actually just did that yesterday, I pulled it off the intake, cleaned the the little o-ring gasket, and sprayed some MAF cleaner into a rag and cleaned around the hole, no change.

Then its the sensor itself. was it covered in oil?

Yea, it had some oil on it

swap it. the only thing that controls your tune is the IAT and Map. the O2s really dont do shit. stalling and shit. try for that first.

Speed density FTW!!!!

just replaced the map sensor.....still doesnt idle right, it started up and idled fine, but i took it down the road, and now shes idlin at 1500

I have an a4, and for what its worth, if i put my car in N and roll up to a stop it will idle around 1200-1500 until I come to a stop, then it will drop and idle around normal. Still trying to figure it out, seems like we have a couple similar problems but not all. If i figure it out ill let you know what to try.