Has your gas mileage gone up recently. If it was stuck open the car would be running very rich and the reading at the EHA would reflect the computer trying to lean out even if it was stuck open, the system would try an lean it. So check your EHA readings. Also your emission gases would be pretty bad too.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)