1991 ToY Camry Nox Emissions Failure ?

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I have a 1991 Tot Camry with 130K miles and till yesterday everything with that car was perfect. I had a major tune up done 6 months ago and I didnt have a doubt that I will pass the inspections. I failed. :banghead:

Nox emissions was 700ppm over the limit. All others were below.

Nox: 1767/1088
HC : 2/141
CO : 0.95/0.79

Now what could be the issue. EGR valve. Do they have EGR's in 1991 camry's. Should i adjust my carbu. How much will it cost ?

I would appreciate any guidance.


posted by  vigoyal

From what I understand, several issues will contribute to high NOx.

1. Malfunctioning EGR system (including carbon build up in EGR valve)
2. Excessive vacume leaks between MAF sensor and engine (throttle body leaks, manifold leaks, leaks around fuel injector O-rings, etc.)
3. bad coolant temp sensor, O2 sensor, etc.
4. Ignition timing out of spec.

I understand the frustration - I own a 1990 Buick which has to be emmssions tested here in Tennessee for the first time since the car was built.

posted by  tbaxleyjr

I know the original post is old, but the problem continues for many of us, so I'd like to comment.

Guess what---drunken gasoline is no help to your old car. Never was designed to be flooded with booze and the government wags know it.* E10 ethanol laced "gasoline" increases NOX emissions by 15% in the atmosphere. Didn't exist when your car was built. E85 is an environmental nightmare, but hasn't gotten much press. I have two older vehicles which performed fine until the proliferation of drunken gas. You couldn't CO poison yourself with as clean as my engines run, but the NOX is going ever higher. The new fuels also deposit more carbon----so pollute the environment by using a top end cleaner (smokes and stinks like crazy, but blows out the carbon!) and then you can more easily pass the e-check test. (GM markets a top end cleaner and another common brand to be found is SeaFoam---most auto parts stores).

* here's the proof they know about ethanol:


posted by  Vonda

A car not designed as a flex fuel will not pass emissions when burning e-85. There are subtile differences in the air fuel ratio and other combustion characteristics the ECM must have algorithims to ensure proper combustion takes place.

Additional studies are required (stated in the paper) since there was no control on other variables. Almost any air pollution control effort has various issues - fix one issue and cause others.

posted by  tbaxleyjr

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