About 10 days ago my car was idling very rough. Took out the Acutron scanner and got several different codes. P0171, P0174 - system too lean, bank 1 and bank 2. The car was drivable, so I cleared and re-read the codes for 2 or 3 days. I kept getting different codes, P1083, p1084, P1347, P1348, etc. Basically codes were pointing to cylinder misfires, cylinder cut-offs, and running lean. I removed the MAF (Mass Air Flow) sensor, cleaned it, and I had some very minor improvement. Checked for intake leaks at the same time, found none. Codes are still flying, so next day I changed the plugs and the #3 coil pack. #3 seemed to have the most misfires. Old plugs were in decent shape, no improvement, still throwing codes. Finally stumbled upon a post or 2 that mentioned the DISA valve.
Removed the DISA valve. BMW calls it 'adjuster unit', also have seen it called 'manifold adjuster'. The plastic hinge pin was broken on mine, so the flap was just hanging there inside the intake manifold! What a poorly designed piece of garbage. Apparently, the flap remains closed, restricting air intake, until higher RPM's, then it opens to allow more air flow. The valve is not variable, and is either all the way open or all the way closed. Mine was hanging open - running lean. I was very lucky no parts had flown off YET.
Replaced the valve (BMW - $220), problem solved - car runs great and no more codes! I would guess mine was on it's way out for some time.
Not a bad thing to check regularly, very easy to remove. Pull the air box, unplug the unit, and remove 2 #40 Torx bolts. The thing slides out towards you. Remember, the same folks that gave you the plastic impeller on your water pump, and the plastic radiator, also gave you the plastic DISA valve, with one plastic and one metal hinge pin. Deteriating parts enter your intake manifold. Brilliant!
Jerry
Removed the DISA valve. BMW calls it 'adjuster unit', also have seen it called 'manifold adjuster'. The plastic hinge pin was broken on mine, so the flap was just hanging there inside the intake manifold! What a poorly designed piece of garbage. Apparently, the flap remains closed, restricting air intake, until higher RPM's, then it opens to allow more air flow. The valve is not variable, and is either all the way open or all the way closed. Mine was hanging open - running lean. I was very lucky no parts had flown off YET.
Replaced the valve (BMW - $220), problem solved - car runs great and no more codes! I would guess mine was on it's way out for some time.
Not a bad thing to check regularly, very easy to remove. Pull the air box, unplug the unit, and remove 2 #40 Torx bolts. The thing slides out towards you. Remember, the same folks that gave you the plastic impeller on your water pump, and the plastic radiator, also gave you the plastic DISA valve, with one plastic and one metal hinge pin. Deteriating parts enter your intake manifold. Brilliant!
Jerry