Emission Failure on 1992 Camry

toyota
camry

#1

My wife 1992 V6, 3.0 Toyota Camry just failed Emission test in AZ.

HC = 1.82 (MAX allowed = 1.00)

CO = 60.24 (MAX allowed = 12)

NOX = 0.33 - passed - Units are all in GRAMS/MILE.

Note: Tune up 8 months ago; O2 sensors (Banks 1 and 2) replaced about 1 yr ago; new oil change and drove about 20 minutes before the test. Car is in BASIC good care condition. Clue: Check Engine Code = 25 has come up about 1 month ago.

Please give me some ideas, thanks.




#2

The obd1 code you mention is a lean code. The cause of the lean condition, or the perceived lean condition needs to be ascertained.


#3

Why does it have a “lean” code (both banks?); but, the engine has “rich” emissions readings?
If the MAF / MAP tells the engine computer that the air flow is more than it actually is, the engine computer will order too much fuel (rich).
If the engine coolant temperature sensor tells the engine computer that the engine is cooler than it actually is, the engine computer will order too much fuel (rich).
If the oxygen sensor reports the engine lean, the engine computer will order too much fuel (rich).
Clean the MAF (if it doesn’t have MAP) with MAF cleaner. Clean the throttle plate and bore, and idle air control valve passages, with Throttle Body Cleaner.
Check the sensor using the instructions in the repair manual.