hat85

Hi my 92 ES300 is having problems passing smog.

After an oil change I tested the car for the first time and it failed Hydrocarbons & NOx, but passed CO with the following readings.
@15mph: HC=122ppm (max=108), CO=0.01 (max=0.71), NOx=1770ppm (max=537)
@25mph: HC=90ppm (max=83), CO=0.00 (max=0.58), NOx=1841ppm (max=494)

I then cleaned the EGR valve with seaform, ran some seaform through in the gas, had the timing set to manufacturer specs (it was at 12, instead of 10) then retested. Here are the second tests results. Note that the CO now failed and the NOx passed

@15mph: HC=158ppm, CO=0.99, NOx=87ppm (max allowed=537)
@25mph: HC=144ppm, CO=0.94, NOx=103ppm (max allowed=494)

I then changed the PCV valve, spark pluggs & wires. I checked the engines compression, and all the valves were about even at 180psi except for one that was around 170. Before the third smog test the check engine light came on and flashed for the Mass airflow sensor. While swapping the MAF sensor with a used one I noticed a crack in the Fresh Air Intake Hose that connects to it, so I changed that as well and the light disappeared (I'm thinking it was probably the hose that sparked the check engine light in the first place). I retested the car and get similar results to the second test. The HC and CO may have been a little lower but they still failed. I don't have the exact numbers right now.

I was told that it may be the Catalytic Converter, but I'm skeptical because of the low NOx levels. Can it still be a Catalytic Converter problem with the low NOx levels?

Thank you