I have a stock 1994 chevrolet camaro. The motor is a v6 (3.4l). The vin is a s code. The car has 154,000 miles. The car runs fine but my problem is for the life of me I cant get it to pass the smog check here in california.

I've taken it to the smog place several times and has done alot of work to it (myself) and everytime it fails for the same reason. High NOx. It is reading 1100 ppm to 1400ppm and with almost 0.00 co. Nothing I do seems to change these readings. I know that this means either two things. the combustion chambers are hot and/ot the mixture is running lean.

Now I need to tell you all the things I have checked and replaced. Hopefully someone can steer me to something I may have missed.

I installed a brand new catalytic converted, (e.o approved/ 3 bed type)
I replaced the EGR with a new one (twice)
I replaced the spark plugs with the factory ac delco. 43tsx
new plug wires, air filer, fuel filter.
I installed two new ac delco oxygen sensors.
installed a new coolant temp sensor and MAP sensor.
I replaced the intake and tbi gaskets (all of them)
Checked to make sure I hav no vacume leaks spraying carb cleaner
Ran a bottle of sea foam through the intake to clean the chambers
Changed the oil and flushed the coolant.
removed the egr and verified open/ clean ports. Did the test to make sure the solenoids are opening approprately and that the egr will stall the motor.
ckecked to make sure i was getting the right fuel pressure (40 psi)
tested the fuel pressure regulator. (ok)
removed the fuel injectors and sent them to a shop to have them flow tested and cleaned.
verified the by listening to each injector to make sure they all were firing.
I have disconnected the battery to clear the ecm memory.
I never have any trouble codes and the car idles well and has decent power.
I have an ethos scanner and I have looked at the o2 sensors as well as the coolant and map sensor graphs. (they look ok)
The blms run slightly over 128 normally. but equal left and right.

and the funny thing is I took the car to the smog place. and with the fuel pressure regulatoy plugged the blms swapped to rich running less than 128 and the car still failed running high nox.

I just can't find a way to get rid of the hot/ lean condition of this car. I hope there is something I can do aside from tearing the motor down looking to clean the cylinders of carbon. I was thinking maybe the fuel pump isint giving the correct volume but passes the pressure test. I don't have the specs (gpm) to perform this test. And I am not wanting to replace too many more parts just for the sake of it. I hope someone readings this can help. thanks greg

 

with everything i know and have learned, you went down the correct path to try to eliminate everything. im not familiar with cali emissions, but if its reading too high of nox, its going to be something along the lines of carbon build up creating a higher compression. have you done a cylinder leak down test and compression test to check the condition of the rings and valves?

 

The only thing I can add, is that you may want to try filling the tank with premium fuel, or even better 100 octane unleade if you can find it. The high octane fuel burns slower and cooler, and may be enough to pass inspection.

 

Fail an emissions (smog) test? READ HERE! - Z06Vette.com - Corvette Z06 Forum

 

Methyl Hydrate is another name for methanol. When mixed with gasoline it slows the combustion process and burns cooler than straight gasoline which should help lower NO emission, similar to using racing gasoline in a low compression engine. The stuff is pretty toxic but makes good racing fuel if you burn enough of it. Also mixes well with notromethane, but that is another story.

 

Yes it is. And, you can buy it at Home Depot in the paint section, it's used as a shellac thinner. Home Dopey doesn't sell "methanol" though. I'm gonna go out on a limb here too, and say that chugging a dose of shellac probably wouldn't be any better for you than the methyl hydrate is.

 

Agreed, but after chugging shellac the internals will be nice and shiny for the medical examiner to look at.