I failed an emissions test, could it be because I didn't warm up my car adequetly before testing?

You definitely want to be up to normal operating temperature, at least. How warm was it when you had it checked? You shouldn’t need to drive for more than 20 miles to get it ready.

In the past, when I had a “near miss” on my emissions, the checker told me to go run the car on the freeway for at least 20 minutes. It worked! I passed when I returned.

Typically when your catalytic converter isn’t warmed up enough, your car will put out a lot of pollution. That’s why driving around on the freeway works. If you spend a lot of time idleing while you are waiting for your turn, you run the risk of cooling off your catalytic converter. I’m not sure if it would work, but you might consider gassing your car while you are waiting in line to give your car the best chance at passing.

I’ve got friends with crap cars that they will literally drive around the city loop and go through inspection until they get their emissions under the acceptable ratio.

My SO love old clunkers that you would never beleive would pass inspection and before testing he always uses this. He swears by it. You might want to give it a try.

Warming it up helps, and so does changing your oil before you go. I always do that and never fail any smog tests.