I have to get the B4C to pass the emission test before I can get the title changed, so I went to the inspection station and had it tested. It did not pass, it failed the low speed test on HC and CO(%), It did pass the high speed test.

.......standard.........my reading
HC...... 117 ...............149
Co(%) .....65..............2.70 ouch

So any ideas on helping it to pass.

What would cause Nox to be high????


350 5 speed headers.
I got a new O2 sensor and plugs to put in tonight and will back off the timing and fuel pressure. All of the emission equipment is on the car.



Any other ideas would be appreciated.


I changed the oil, pvc and fuel filter yesterday.

This is inTexas, Tarrant county so any of you all living down here get ready, the guy at the inspection said a lot of cars are failing.

 

don't back off your fuel pressure that won't help if not make it worse unless you have it set high. The computer will enrichen dump more fuel in there when it sees a lean condition, all the while causing poor fuel atomization. Also when you check your fuel pressure, make sure it holds it. If not you may have a leaky injector somewhere down the line........

 

I need to do that and see if it might be a leaky injector.
The fuel pressure is set to 38 lbs, it's on a 305 Z motor.

 

And they call older 70's cars GROSS polluters

Three readings high, yuck!!!!

CO is incomplete combustion and that comes from rich mixtures.

HC is unburned fuel and they come from misfires, bad quench, and leaky exhaust valves.

NOX comes from lean mixtures and high combustion temperatures.


First do a compression test to verify that the engine is mechanically sound. If there are dead holes, that is your first concern.

Verify timing of the engine and tune.

 

Add about 10 bottles of dry gas (Isoproyl alcohol) to a 1/5 tank of gas. If you have A/C, make your secondary fan the primary (the hotter temp will reduce the HC levels, slighty raise the NO count). Also, changing the O2 will reduce the Co%.

In your case, just do the dry gas and O2 sensor for now.

BTW, I had my camaro inspected last saturday, my results:

NO limit-> 1046 | result->658
HC limit-> 140 | result->51ppm
CO% limit-> 0.79 | result->0.02

AFR 58cc 190's, ZZ3 cam, 1.6 RR on the intake side. Catco cat and egr. 220-230° (factory guage reading) coolant temp. No dry gas . 3 year old bosch O2 sensor.

2 years ago with the stock heads and dry gas the HC was 14ppm and NO was slightly less.

 

Thanks guy's
I went down and had new cats put on the car, one had 3/4 of the stuff missing.