Greetings

My 1989 740 GLE station wagon (clean clear coat paint) (364,500 MILES) with aw-70 A.T. NON-Turbo passed on emissions with exception to the NOx portion. It passed on H.C. grams 00.87, state limit= 02.00, on the CO grams per mile it read 008.73, state limit= 030.00 on the NOx it read 05.05, state limit= 03.00. The stated that it might be a timing,ignition, exhaust, 02 sensor, and or EGR issue. Well let me tell you the car is in excellent shape! I use nothing but premium fuels, change the oil regularly (Chevron Delo 400 15w-40) during the summer and Chevron supreme (winter)and synthetics! I keep a strict maintenance regimen, and the car has new exhaust, flame trap, plugs (NGK V-Power)etc. They also stated that it may be a cat issue! This car runs so smooth, and my gas mileage is roughly 27-30 mpg! My driving consist of 98% highway miles! Might it be a timing belt issue (loose and or in need of replacement) personally I think a bucket of you no what is being dumped my way. The said they had mechanics that could help resolve my issues etc. I am very mechanically inclined, however again, I believe the are full of hog wash! Oh and the car neither leaks nor burns any oil! The plugs are firing clean and normal. Might it be the higher sulfur content in the 15W-40 delo 400? Should I just swap back to the 10w-30 for the moment? What benefit would it be for me to drive the car for a good 45 minutes via highway and then bring it right back for another emissions test, would that shift the NOx readings in my favor? Again I passed everything else regarding emissions and safety,its just the silly NOx readings! My apologizes for such a long thesis, please help! Mr.Foster of Cape Cod are you available?

1988 740 GLE S.W. 425,700 MILES (same as above)
1989 740 GLE S.W. 285,000 miles (same as above)

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Thanks in Advance!


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