QuestionI had my 1992 cad DeVille 4.9 liter V8 smog tested for registration renewal and it failed. The test results shows it passed everything except
"NO ( PPM )". I don't know what that means and how to resolve or repair it in the least expensive way. Do you have any idea what the in the world this means? What is "NO (PPM)" ? Is this something I can easily fix or repair myself. Your help is very much appreciated.
AnswerHi Ron,
The thing that come to mind is this. NO: means NOx or nitric oxide. And the PPM is parts per million or how much NOx is in the exhaust gas.
NOx is a by-product made when the engine temperatures get hotter than normal. If your temperature gauge is reading higher than normal then that would verify it. The normal things for running hot need to be checked and include:
rad cap can't hold pressure
coolant freeze point needs to be around -34 degrees
thermostat opens all the way and when it should
nothing is blocking airflow through the rad
cooling fan turns on when it should
egr valve opens up and the engine runs rough if you push it open at idle, the egr ports could be plugged.
the intake air door should be open to allow outside air to get into the engine instead of hot air from the exhaust manifold.
Once those things are checked then I would retest and see if it passes. If not then go to your mechanic for a diagnostic and see what needs to be fixed or replaced. At that point you could do the repair yourself or have them do it. Hopefully they have a tester to make sure the NOx ppm is in the passing range. Bill
