My 1992 Previa 1992 didn't pass the emission test. Check engine light not on. The NO level is too slightly high. It need to be 956 or lower on the 25/25 test and it pass on the 50/15 the first time.


Asked by Dec 31, 2011 at 08:09 AM about the 1992 Toyota Previa 3 Dr LE Passenger Van

Question type: Maintenance & Repair

It's running fine. Although my oil light came on and I know the oil needs to be changed. Would that be the cause of it not passing that part of the test? I changed the gas filter and put some fuel injection cleaner in the tank and drove half a tank of gas through and it when down on the 25/25 test but not enough to pass but then the NO went up on the second test. What do I need to do to fix this problem?

4 Answers


okay, this may not sound real technical and I certainly cannot explain why or how it works, but here is what I did, and never have a problem passing emissions. Local auto supply store carries a product called "guaranteed to pass", its some type of fuel additive that costs around 20$, and if you use as directed and don't pass, you get your money back. I was skeptical, until I used it. And recommended it to this or that friend, who also found success with it. Thats about all I can suggest to you, all the other emissions repairs are fairly spendy and I wanted to exhaust all other options before taking that route. Fortunately, I did not need to! Hope it works for you.

1 people found this helpful.

Thanks for the information, it used to be sold at Walmart but they don't carry it anymore. I brought some Lucas fuel injection cleaner for $9, changed the gas filter, and got my oil changed.It passed.

1 people found this helpful.

Excessive NOx is produced when the combustion temps inside the cylinder are too high. Introducing exhaust into the intake lowers these temps. My 1993 Previa failed the NOx test because the small passage through the intake manifold, from the EGR valve, was stopped up with carbon. I had to clean that passage out with a sharp pick and carb cleaner, so the EGR valve could pass exhaust into the intake manifold. This was a few years ago, but as I remember, it was kind of a headache because I had to unbolt the intake manifold to get to it. I also had a 1989 Ford F150 that failed the NOx text every 2 or 3 years. The EGR valve on this truck would get plugged up with carbon, and I had to take it off, and break it free. The cone shaped valve on the EGR was made out of tough metal, so I could tap it with a hammer until it broke free. I then used carb cleaner to flush it out. I had that truck for about 10 years, and this consistently happened, but it always passed after doing this.

2 people found this helpful.

Thanks Larryboy89, but once I got my oil change and drove some more after changing the gas filter and putting some Lucas fuel injection cleaner in the gas it passed. Thanks for the information.

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