A6AvantErik: MCS

would this have anything to do with the car having a rough idle / very low idle that is about to stall? Its gotten worse throughout the night, whenever I stop at a stop light, the usual idle is at 800 rpms, at this point now it is idling at about 500-600rpms/min...
I'm getting the car checked out on tuesday for other reasons, but I'm wondering if this EGR flow CEL would have anything to do with the rough idle/stalling. It has stalled in the past few days from idling for over a few minutes sitting in a parking lot/driveway about twice. but no dying tonight, just very low rpms, rumble of the engine, and shaking (because of the low rpms) but not dying

Just for specs- it is a 97 a6q automatic.

TIA

austinado16

....and the computer only tests it's function under one condition: 45mph-62mph(or something like that) with steady throttle. The computer then starts a timer and looks to see that the EGR temp sensor hits 65*C in under a minute. If it does, the CEL is not turned on. If it doesn't, the CEL is turned on and the insufficient flow code is thrown.

A few things can be causing your rough idle.
1)Bad injector spray pattern
2)Idle Control Valve not functioning properly
3)Vacuum leaks from anywhere in the intake track
4)EGR valve either receiving vacuum at idle, which it should not, or the EGR valve is stuck partially open and leaking exhaust gasses into the intake plenum at idle.

#1 can be cured with an induction service
#2 try cleaning the inside of the valve and if that doesn't work, replace it.
#3 look for bad vacuum hoses, and spray around all intake areas with carb cleaner with the engine running. Anywhere you get a change in idle is a vacuum leak.
#4 unplug the vacuum line going to the top of the EGR Valve. If the idle improves, you know you are getting vacuum through the line at idle....and therefore have a bad EGR Solenoid Valve over there under the air filter box. If the idle doesn't drop (and you don't feel vacuum at that vacuum hose, smack the top of the EGR valve and see if that changes the idle. If it does, you know you have a bad EGR Valve that's sticking open. Replace it.

Save your money and do all these tests yourself and report back. Spend the money you save on parts from www.autohausaz.com and install them yourself.
Hope this helps.

heybiff

ODn't forget the passage to the EGR valve and TB could be clogged, causing CEL as well

austinado16

True...all kinds of EGR CEL causes. I was merely commenting on the poor idle