I'm having problems with an erratic idle on a '99 Impreza RS SOHC 2.5L. This is the first SOHC 2.5L with the MAF system.

It acts very much like a vacuum leak...hunting up and down ..not severely,...just a little...and sometimes it slows enough that it acts like it might even stall..but doesn't. Also seems to be running a little rich...tailpipe is sooted up.

An OBD-II code reader shows trouble code "P0106 -Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem ".

I've checked the hoses to the Atomosperic Pressure Sensor mounted on the passener side shock tower and they seem OK...no cracks.. The hose is a little loose fitting on to the intake manifold...but tightening it down with a good zip tie doesn't seem to help.

If I disconnect the little hose that goes to a small vacuum nipple on the intake manifold, and plug up the nipple with my finger...sometimes it seems to improve my idle....but sometimes not......

I'm stumped.

Can anyone shed some light on the purpose, function, malfunction of this device....and possibly how to fix it.

Warren C.