I have a 1997 Avant with the 2.8 -- C4 body.

It runs great most of the time EXCEPT I am having a small problem. It stops running once in awhile and sometimes runs rough like a cylinder or two have dropped out. I have no problem restarting it when it stops and the if it runs rough I just pull to the side of the road shut it off, restart it, and everything is OK except for a CEL. The last codes were P1101, P1106, and P0302.

P1101 and 1106 are the first O2 sensor on each bank or massive vacuum leak. P0302 is a misfire. They clear with VAGCom but it happens again in a few thousand miles.

I don’t think two O2 sensors would have an intermittent problem at the same time so I suspect something is hanging up and causing a large vacuum leak.

I haven’t a clue as to what could be causing it. Any ideas??

PS I know the EGR hangs up once in a while and throws a low flow code that is easily reset - but I don't see it when the motor stops.

 

At 240,000 miles the wiring may be a possible cause. Sometimes the terminals are corroded. Sometimes the wires break from vibration. The chassis ground terminals may become corroded. The idle control valve may need cleaning.
Check your emission monitors with VAG COM. After you reset the codes, do the monitors come back up? Check your ignition switch. Check your fuel filter.
Why does restarting the car make the problem go away?

 

I can't remember if the older motors run a MAF or not, but have you tried disconnecting it to see if it runs better? If it had that big a leak you should be able to hear it with the hood open. The codes are too consistent to be a wiring issue, unless its a wiring problem to the MAF.

 

MAF connection might be the problem..
The first time it happened was just after I changed the air cleaner

 

You're on the right track, unfortunately the only way to check those wires (short of visually) is to use a pin out box from the ECM to the connection point at the MAF. Only a certified audi shop will have a pin out box. If the MAF is old i would just replace that first, if it doesn't fix it then it needs to go to a shop to be traced. You "MIGHT" be able to check it with a DVOM if you can figure out which wires on the ECM connector are the MAF wires, a bently manual should have the wiring designations, but a pin out box makes it so much easier.