You don't say what State you are in, so I don't know exactly what test you took, but the principles stay the same.

High readings of the NO compounds (NO, NO2 etc) are due almost entirely to HIGH Internal Cylinder Temperatures. i.e the internal cylinder temperature has gone up to over 2400 degrees F.

There are multiple reasons for this, but the most likely is a lean mixture.

The CO reading is extremely LOW, coupled with a (relatively) high 02 reading, so a lean condition is certainly indicated. The CO2 reading of 12.6 indicates that the engine is either on the rich or the lean side of the ideal (14.6). Bet again on lean

1. Use a can of a good quality Fuel Injector cleaner and go drive a few hundred miles.
2. check all vaccum lines and hoses for leaks.
3. Check the inlet manifold for leaks (squirt carb cleaner around - listen for any increase in engine RPM)
4. Check the EGR valve for correct operation. With the engine idling. suck on the hose that opens the EGR valve. The engine should develop a noticable "stumble" as the EGR valve opens and dumps exhaust gas into the inlet at idle.
5. Check the air pump and air bypass. The Cat needs a supply of oxygen to function. No suplemental oxygen, no cat action.

If all else fails heres a tip for passing any Emission test (assuming the cat works).

Make sure the cat is REAL, REAL hot. Go for a good drive around before you pull in for the test. Do not sit in line idling, as the rich mixture at idle will cool the cat back off.

Good luck

Let us all know how you got on.


posted by 209.81.16...

• High NOx Emission Continues..., Yaofeng, Tue, 16 Jul 2002 13:10:50
  • HIGH NO and NO2 (it's not really NOx), cliff7080, Tue, 16 Jul 2002 17:10:41 <-- Viewing This Message
    • Re: HIGH NO and NO2 (it's not really NOx), Paul Russotto, Tue, 16 Jul 2002 20:10:17
      • RETARDED TIMING, cliff7080, Tue, 16 Jul 2002 21:11:03
  • The CO and HC is almost too good, the engine might run, Anders, Tue, 16 Jul 2002 14:38:06
  • I believe high NOx is often due to..., BillJ, Tue, 16 Jul 2002 14:07:38

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