QuestionMy 1987 cressida has failed emission because the NOX was too high ,I changed distributor cap ,plugs ,new EGR valve new air filter and still failed ,I do not want to get rid of the car ,it is a beauty even though I also have an over heating problem which I was able to control a bit by putting on a new radiator cap,so would you please help me?
AnswerOlder cars like yours with high mileage (not knowing what your mileage is) have an increasingly difficult time passing smog. Many cars that are older require mechanical work (valve job) to pass smog and keep it on the road. If your car was mine, I would run high quality fuel, change the oil more frequently (every 2000 miles) and do more freeway driving (to heat up the catylitic converter) until the date of your retest. If you have the money, replace the catylitic converter and the O2 sensor and the spark plugs before your retest. Please see the list below:
Causes of high NOx readings:
1. Ignition timing too far advanced
2. Excessive combustion chamber deposits
3. Poor cooling
4. Lean combustion due to old or defective oxygen sensor
5. Lean combustion due to clogged injectors
6. Defective catylitic converter.
