05-19-2012, 05:17 PM
Join Date: Jul 2007
Location: Show-me state
My Ride: 2001 BMW 330I
Did you miss my note earlier that my secondary air monitor was ready while driving away after starting up instead of during idle? I let it idle twice, and it wasn't set.
I replaced the pre-cat O2 sensors, and their signals are vastly improved compared to the graph I posted on May 2nd. However, it didn't have the sudden change of voltage to the rich side I mentioned on May 6 post.
Here is my theory.
I think DME is shutting off the vacuum to SAP control valve, and it monitors the change in voltage of pre-cat O2 sensors. It is expecting a rich conditon (+>0.5 Volt) since no extra air should be supplied to the exhaust side.
If DME doesn't see the change in voltage, it doesn't set the secondary air monitor. My guess is that SAP valve is stuck open or too much gunk in the valve is preventing the valve from shutting off completely.
So my recommendation is to drive away (give a bout 10 seconds) after starting up, and try to stay below 2500 rpm until the SAP operation is done.
I see a little bump you mentionied, but it doesn't look high enough like mine or shennabe's. If drving away doesn't work, please check SAP valve if it is clogged up.