My 1989 240DL wagon failed inspection with NOx emmissions double the passing value. A guy at the inspection station and a local mechanic said the most likely cause was the catalytic converter.

An EPA study (http://www.epa.gov/otaq/regs/im/obd/p01003.pdf) referenced by Paul Grimshaw - Passing Annual Emissions Tests (Part 2) (http://www3.bc.sympatico.ca/Volvo_Books/engine10.html) indicates otherwise. The only repair that matched the emmission test data was EGR related. It makes sense intuitively since that control's purpose is reduction of NOx emmissions.

Well, dah, I haven't been able to locate anything that looks like an EGR valve or sensor. After hours of pouring through the Haynes manual and countless searches it isn't even clear if this car has an EGR valve. The EZ-116K electronic ignition control unit performs the function electronically.

There is an unidentified hose that goes from the intake manifold through the firewall to a plastic sphere under the radio (????). I suspect that the air control valve could be part of the mystery.

Any information and/or links would be appreciated. I have not found any pictures or diagrams for this engine configuration.

Thanks,

David