98 4cyl failed smog test

My 98 Voyager, with 154,000 failed smog with high NOX and borderline high CO, HC was OK. High NOX points to lean mixture but high CO points to rich mixture. Timing is not adjustable. Any ideas?

if timing isnt adjustable and egr operation is fine, and o2 sensors are working how they should (not lazy etc) then its gonna need a cat.

meezy09 is correct. The California spec car does not even have EGR (although the alldata manual says it does). I replaced the catalytic converter, and emissions dropped to near zero. The car passed smog with score like a new car.

Too bad that there are no aftermarket catalytic converers for California cars. The cat cost me $612.

I read you can put 2oz of acetone per 10gallons of gas in your tank
The acetone is diluted to non-dangerous to plastic/rubber components, but it does allow the fuel to atomize better and burn much much cleaner (as close to a perfect fuel as propane)

http://peswiki.com/index.php/Directory:Acetone_as_a_Fuel_Additive
http://pesn.com/2005/03/17/6900069_Acetone/

I would recommend doing your own research..I have been running this mixture in my 1992 Dodge Dakota with absolutely no bad side affects...truck idles and runs smoother

Brian
AwPhuch