I hope somone can help me with this problem. I have 91 RS with 305 fuel injection. The car has 184,000 runs good despite the mileage. I fail N.J. emission last week (Nox) was 1202, standard is 907. Found out the EGR valve was bad so I changed it. I also retarded the timing because the car was pinging on regual fuel. The last thing I did was drop a can of G2P (Guarantted to Pass) I figured at least it would clean out the carbon in the car. By the way prior to the test I changed to plugs, rotor, filter and pvc valve. When we brought the car back to retest the emission the NOX went from 1202 to 461. Great it passed that test. The problem is that HC and Co both failed they went from 71 to 163 for the HC and 0.06 to 1.51 for the Co. Anybody have any ideas? Thank you in advance.

 

You traded one for the other. Most likely that was the timing change. How much did you back it off?

What often happens with these cars is the EGR passages get plugged up with carbon. The only way to clean it properly is to remove the intake manifold. The pinging most likely was due to the inoperative EGR system (note I didn't say "EGR valve"). Retarding the timing "fixes" the pinging, but at a price.

The other possibility is a poor O2 sensor. That will raise HC and CO. But, so will excessively retarded timing.

Of course, this is all just a WAG, but it is based on some general trends.

 

How old is the CAT on your car? If its old I would replace it. Also make sure that the air tube that goes to your CAT is connected. The CAT need the air to help with the emissions. And make sure you get the car good and hot before the test. And like five7kid said. change your O2 sensor also.

 

Iam so glad we don't have to put up with Emissions

 

Thank You I will recheck the timing on Saturday.

 

I was able to time the engine on Saturday. I disconnected the ESC wire (brown) and timed the engine TDC 0 degrees. Should the timing change when you reconnect the ESC? The reason I am asking is because it did not. The timing remained at 0 degrees. I was under the impression that the timing mark would advance once I reconnected the ESC. Could there be something wrong with the ESC? On the older cars we used to disconnect the vacum advance before timing the engine.

 

Check the timing after you shut down and start the car back up.

 

I am going to say that without a doubt, it was the timing change that caused your engine to over-fuel and fail the test. You pulled some timing out, that lower the manifold vacuum, which causes the MAP voltage to increase and the ECM to inject more fuel. With the the timing at 0* with the Timing wire disconnected and all will be good there. If it is still pinging, try a GM TOP engine cleaner or Sea Foam. Finally, put some premium in the tank!

 

This may be a dumb question but...

Will 93 octane make your car run cleaner with the timing set to 0*? Or will it run cleaner running 4* advanced and 93 octane?

 

higher octane doesn't really burn cleaner

it stops detonation by not pre-igniting, which will hurt emissions greatly. so by not letting your car ping, yes it burns cleaner.... kind of.... its not that the gas actually burns cleaner though.... lol

I'd leave it at 0* and change my O² sensor... that will probably pass you.