It's a 1990 244DL.

A few weeks ago, I would get the codes 113 and 232. The engine would, at the same time, run a little rough but would always idle at 750 RPM. I cleaned, checked and retightened just about every vacuum hose, connector, relay, fuse and ground in the car. I disconnected the battery, reconnected and voila, the problem went away - for about 500 miles. The codes came back. I disconnected the battery and voila - the problem went away. I've since driven about 300 to 400 miles without a problem. Until yesterday.

I started the car up fine. I drove about 1/2 a mile in stop and go traffic. Suddenly the idle would hunt. I was watching the tach. Where normally it would stay rock solid at 750 - it was now dropping to below 500 then up above 750 then down again etc, maybe 5 or 6 times until it would stabilize itself. The trouble seemed to occur when I would quickly decelerate from say 15 to 20 MPH to 0. I thought maybe a vacuum trouble relating to the booster check valve, but visually it checks out (the hose as well). I thought it helped to slowly decelerate. As if when I would slow down over 75 feet to a complete stop it would help. And it did somewhat but not entirely. If, while at a stop, the engine was hunting around, and it seemed like it was going to die, I put one foot on the brake and the other on the gas bringing the idle to 1000 RPM or so, the car's engine would run fine. This last fact leads me to believe that the IAC is faulty. Just to recap, I've changed the FPR and main pump / filter / complete tune-up etc. Recently. Any thoughts are appreciated. I just don't want to throw parts at the problem without diagnosing the exact problem. Thank you.