Quick question on Emissions Testing

[crawdad]

I've never had to have an emissions test on my truck before, however, I may have to have one pretty soon. I'm just curious as to what things would cause a truck to fail emissions? What do they look for and what are some things that I could do, i.e., tune up, etc., to insure I pass the test. Thanks as usual for your help.

[blink32]

The single best thing you can do is make sure the vehicle is completely warmed up. After that its basically what you mentioned, a tune up (whatever that entails for your particular vehicle), and make sure you know what the laws are for your area. Some places you must have all original emissions equipment installed, some places you only need cats and still others don't care as long as you pass the sniffer test.

Most of the cars I've had or seen fail emissions were from running too rich. Either the air/fuel ratio was effed or the O2 sensors weren't operating correctly. Replaced/adjusted and they passed fine.

[Zoomad75]

Having the engine in a poor state of tune will fail all the time. Like above, depending on the local laws, if you are missing emissions equipment they will fail you.

Prep is to make sure the parts you need are there. So if you got a nice chrome open element air cleaner, better have a stock one to put back on. The stock one has the hot air stove to the manifold among other emmisions parts. Give the engine a good tune up. Plugs, minimum but cap/rotor/wires if it needs it. Set the timing correctly and if you can, lean the carb out a little at idle. As stated before get it WARM. If the engine isn't burning oil, you'll pass easy.

Now, if you are burning oil. Even if it's valve guides the sniffer's going to pick it up as extra HC (hydrocarbon) emissions. If they don't fail you for that, they might catch you for the visible smoke. (another reason to get it nice and warm) Having been able to get my Nova to pass the test in Denver many times with a hopelessly worn out 307, just about anything can pass. Besides the prep work mentioned above, also change the oil, preferebly to 20-50w if its using oil. Thicker the better (your going to change it again once you pass). Go to the local parts store and get a bottle of Wynns Smog Check. Follow the instructions on the bottle and add to your gas tank. Once in the tank, get the engine right up to operating temp and go straigt to the testing station. I don't normally fall for those fixit in a bottle snake oil bits, but the wynns stuff worked every time (but I did make sure it was ready with the tune up first). Before I was failing on the HC and couldn't lean it out anymore.