I’ve got a '95 Nissan Sentra with about 108k miles on it. It failed to pass emissions today, and I’m wondering if there is anything I can try to do myself and have it retested before I take it to a mechanic.
The specific test it failed was for NOx. The maximum reading to pass is a 2.0, and it got 2.4885. I don’t know if that if is a real bad score, of if it was close to passing or what.
Although I do have an appointment at a mechanic for next Wednesday to have this looked at, I’m considering trying to get it retested before then to see if I can get lucky. Is this a good idea? In my state I’m allowed 2 free retests, so I guess if it still failed I could bring it to the mechanic and assuming they fixed it on the first shot I’d be OK.
One thing I know for sure my car needs is a new air filter. The one in there now is very dirty, so I’m getting a new one tomorow. Could this help?
I’m also considering filling it up with premium gas before I get it retested. Is this worthwhile?
Any other suggestions, or easy things to look for? Is it even a good idea for me to try this stuff myself, or am I just wasting one of my free retests?
Here in Ohio there was a scandal when an undercover investigator discovered that x (x being a high number which I can’t recall) of out 10 cars that failed the EPA test passed a subsequent test at a different testing facility. No work was done to the car; the dude just drove to the next station and had it tested again.
So, yeah, I’d take it to a new station and fork out the twenty bucks (or whatever fee they charge in your state) to get it re-tested before I spent large American dollars to get it repaired.
NOx occurs when combustion gets too hot. (I’ll leave Una to present the exact temperature. )
Three things produce a high NOx reading:
Lean combustion (too much oxygen).
Faulty exhaust gas recirculation (again, too much oxygen; the oxygen is not displaced by “dead” air).
Malfunctioning 3-way catalytic converter- catcon notsplitting NOX molecules into free nitrogen and oxygen molecules, respectively.
My husband’s car failed the local emissions test, and we paid a local garage to have it looked at/fixed. It turned out that the culprit was a gas cap that had a “door” so he could fill the tank without actually having to remove the gas cap. (This was a replacement cap that we got when he forgot to replace the original gas cap after filling up the tank one day.) We paid something like $75 for the repair person to let us know what the problem was.
I doubt it applies here, but if you do have one of those gas caps, you might consider putting the original cap on for the re-test.
A can of Techron fuel system cleaner in the tank couldn’t hurt, might help. It’s a long shot, but it’s cheap (and not a bad idea for maintenance anyway).
Don’t use premium fuel prior to an emissions test. It burns slower than regular and you will end up with unburned fuel in your exhaust. This will guarantee a test failure. My brother found out the hard way a few years ago. He had a Dodge Dakota that required regular, he would use higher grades of fuel claiming better fuel mileage. The pickup failed it’s first two tries so my brother took it back to the dealer, it was still under warranty. The mechanic determined the problem from the test report and my brother ran a couple tanks of regular and it passed emissions. He also found out he got better mileage using the correct grade of gasoline.
I did take another shot at the emissions test before I took it to the mechanic, I just replaced the air filter and made sure the car was hot before I took it in. It did get better, but it still failed. The NOx level dropped to 2.2 from 2.48.
So, I took it into the mechanic today and found out it needed 2 oxygen sensors and a catylitc coverter. Total cost would be like 600 bucks which I can’t afford right now. So, I paid for the test and took the car back.
Now, I’m trying to decide if there is anything else I can do myself to get this thing to pass emissions without me having to shell out over 500 bucks. Basically, I don’t know how much longer I’ll have this car for, it has needed a lot of costly repairs recently, and I’m getting sick of dumping money into it.
Anything else I could try myself before I had to bite the bullet and get the repairs at the mechanic? I’ve heard that putting a few bottles of “heet” into it right before a test could help. Any tricks to use to get it by emissions one last time before I (hopefully) get rid of it?
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