High nox on emmission but no engine codes

Are all the error codes ok? Sometimes a minor code will not cause a "check engine" light on the dash. If the ignition system is marginal it will continue. The results of the emmission test help diagnose. Usually Nox is too high. It's usually caused by a very high temp combustion temperature. Carbon buildup in the cylinder may cause. If the cooling system is marginal, it may contribute. Some advocate a decarbonizing effort. Double check all your connections, cleaning and scraping to bright metal may help. I found a disconnected ground wire. It seemed to make the difference between pass and not.

Your uncle could be right. It is always best to make sure you put the correct fuel for your make and model in the tank. Don't put in any additives unless approved by the vehicle manufacturer. The catalytic converter in the exhaust system is what reduces the CO and NOX in your exhaust. It has a catalyst in there which causes certain chemical reactions in the exhaust. Firstly the converter must reach operating temperature, so before you get the exhaust checked make sure your cars exhaust is nice and hot, a five minute drive up to the inspection station first thing in the morning may not get the converter to the operating temperature. The other problem may be as your uncle said. The injector cleaner may have put out certain chemicals into the exhaust that have put a fine layer of residue in the converter. This will block the NOX from getting to the catalyst and therefore stop or lower the reduction. You may have to replace the converter (they are expensive here in Australia) but you should try and take the car for a long easy drive in the hope that it will burn off the residue (if there is any in the converter) and then go and have the levels checked, the converter should be hot enough to do its job by then. You may also want to try another inspection station on the other side of town or another town depending on the distance, that will get the converter to operating temperature and the inspection stations meter may be calibrated better than the one you are going so it will give a better reading!

Google what ever your Emission Report has on it

CO or NOX

ppm ---parts per million
NOX--Oxides of Nitrogen

What Causes High NO NOx SmogTips com

here are the possible causes of high nox levels, Misfire condition
Malfunctioning or improperly adjusted EGR valve
Failed oxygen sensor
Leak in exhaust tubing upstream of converter
Excessive carbon deposits in combustion chamber
Improper spark advance
Blocked coolant passage
Overly lean air-fuel mixture
Damaged cold air duct
Failed or malfunctioning catalytic converter
Corroded or damaged engine sensor electrical connections.the best advice is to take it to a emission specialist to check it out! good-luck!

NOX is usually something like an EGR Valve or engine overheating,at least in the inspection lane.
I don't have the code, but you can see if the Egr is working and pull it off to make sure the passages are clean.
Going to inspection on a cool day helps, and don't sit there idling,shut it off.

means that the hc,co2,nox, emissions are too high, you will need the numbers in ppm on the read out to begin diagnossis

The catalytic convertor could be the issue. A car in bad need of a tune-up won't usually pass smog, either. High emmissions is caused by either a bad cat or unburnt fuel. Start looking at the ignition system (spark plugs, plug wires) and give that thing a tune-up.

the car is older that 1996 there for you dont need emissions testing. if you wish to pass, check the carbon canister and the egr valve. if the temp gauge says the cars not over heating and the engine doesnt appear to be hot, dont worry about it.

Sticking egr will raise everything except nox. Bad o2 bad cat hard to give an accurate diagnosis with out checking it