Code 1222. Lambda control.
 

Hey guys. A new code has come up. 1222. It only comes on when idling, as soon as I crack the throttle the light goes off. Also, idle is a little erratic. Not surging, just maybe idling a little too low. Sometimes it almost wants to stall. I figure this is probably an air issue. Any ideas. It has a new MAF, new crank position sensor. Could it be fuel pressure regulator, or another sensor gone bad? Thanks. 1991 325ix.

Terry-

I had the same problem. Turned out there was a crack in the underside of the intake bellows where the idle control hose connects. Air leak caused the fault. You might want to check there.

When you take it apart to look for cracked tubes, that will be a good opportunity to clean the throttle plate and IAC valve. Also, if you have a voltmeter, check the throttle position sensor.

Thanks guys.
 

I checked the bellows recently and no cracks. I will clean the throttle plate and check the TPS resistance. Does anyone know the range? And additional suggestions? Thanks again.

When you unplug the TPS, there will be three pins showing, they count from the bottom up.

Key on, there should be 5V at pin #1 in the harness plug.

Between pins #2 and #3 on the sensor, you should have 4k Ohms that should smoothly decline to 2 k Ohms as you open the throttle.

I notice that the Bentley manual does not give specifications for the TPS on the OBD II models. They just say to replace it if the computer says it is bad. Trusting an OBD II computer to correctly diagnose an engine problem?? What planet are these guys from?

I would double down on the search for a vacuum leak. The code 1222 is not an oxygen sensor problem, but it's detecting a mixture problem at idle, which is very often caused by a crack in a vacuum line. Double check the intake boot - these crack all the time and you can't tell until you squeeze them. I had a problem like this on my 318 - there was a huge crack, but it didn't show until I squeezed the intake boot.

-Wayne