Failed Emissions Post #9534548

Ok, bombed the GA emissions test in my 94 XJ 4.0. I need some pointers, here are my readings after sitting for 40 minutes in hot Georgia Heat for the test:


25/25 Test

HC: did 104, 159 allowed
CO: did 0.72, 1.78 allowed
NOX did 1877, 1014 allowed <<<<<<<< my problem

50/15 test

HC: did 98, 163 allowed
CO: did 0.69, 1.38 allowed
NOX: did 2110, 1110 allowed

Is this fixable by dumping some of that "snake oil emissions ghetto pass" in the tank?

Can I pull timing for the test to help the results?

Can I run a colder plug?

Thanks!!!

i dont think ths cat. is doing its job. time for replacement.

I'll second that motion. The three cars I've had fail for high NOx with clean hydrocarbon and CO2 readings were all cat failures. Might want to replace the oxygen sensor too, just to be safe.

High NOx usually indicates high combustion chamber temps. Your '94 doesn't have an EGR valve, so it isn't that. Could be a lean burn condition, though. You may be due for an O2 sensor, but those usually result in a rich mix when they fail. Check for vacuum leaks.

The catylitic converter is responsible for NO, thats what I would say is time for a change.

Well, I just found the rubber hose from the airbox-valvecover is off, could this be it???

I also picked up some that Gaurenteed to Pass Stuff........................... :wow:

Can I retard the timing?

No. You can put stock champ truck plugs in, if you don't already have them. I found a noticable change in NOx when I changed. If you want more info, do a search. on emissions.