My friend in SE Texas just failed to get his inspection sticker b/c of high NOx (oxides of nitrogen). He is disabled but able to do a little mechanical work. He passed last year easily. Truck has new oil change, new filters, new pcv valve, new plugs, and new half-*** $40 autozone plug wires. He swears it runs smooth, burns rubber, and idles smooth. He got it nice and hot before going to inspection station including flooring it a bit. 1)Anyone have any ideas on what to check? 2)I was thinking bad EGR valve or bad TBI bottom manifold gasket. Or else, both of those with a lazy O2 sensor and those half-*** wires. Any advice appreciated. Thanks,Michael

 

Failing on NOx usually indicates a temp problem. First thing i would look at is the EGR. It is designed to cool the combustion chamber. If that checks out ok,and it isn't overheating, you might want to look at the converter. If it has the original converter on it, its probably only a 2 stage. You can get a 3 stage converter that will help reduce NOx