Hi,
I have a '95 Camry with 312,000 miles. It hass the 2.2 4 cylinder with 5-sp manual transmission. It failed the emissions test this morning. It failed the "oxides of nitrogen" part. It was allowed 2.00, but it had 2.94. It passed the hydrocarbons part with .39 and .80 allowed. It also passed the carbon monoxide part with 5.46 and 12.00 allowed.

The pamplet they give you when it fails for NOx says that it is either the EGR system, operating temp, air management system, lean air/fuel mixture, catalytic converter, or over-advanced off-idle timing.

No component of the EGR has ever been replaced, the engine does NOT run hot, air management..????, air/fuel mix, maybe I need to replace the air filter, catalytic converter, still the original one, timing, maybe it needs to be adjusted.....

I had a feeling it was going to fail, I remember the last time I had it tested a couple of years ago, it was close to failing.

Any advice is appreciated.

Chris

 

High N0x is caused by high combustion temps.

Has the MPG changed?

How does the car run? Other then failing the test any other issues?

One place to start would be to check the EGR system for excess carbon buildup.

A portion of the exhaust gas is routed into the engine intake to cool the combustion temps. Over time carbon can build up plugging EGR valve passages and causing the valve to stick closed.

 

The car runs great! I don't think the mpg has changed. No other issues ith it. It is still on the original engine. Nothing in the EGR system has ever been replaced.
Is there a way to check the EGR system before I start replacing items?

Will the car still run good if the egr is bad?

 

well, around here, you go to any repair shop, they "look at it", you pay $200 or so and get receipt where it says that "$200 was paid towards emissions repairs". you take that receipt, turn around and go back the station. now, they look at your receipt, nod and shake their heads, ask you to pop hood open, they do "visual inspection to confirm that none of the emission system parts was removed or damaged" - and you get release for 2 yrs. you simply did not ask.

DO NOT WASTE $$ ON "GUARANTEED" TO PASS EMISSIONS CHEMICALS. FAST AND FURIOUS IT BUILDS UP TO SAME AMOUNT - AND YOU STILL DO NOT PASS.

 

Are you going to be doing the work or a shop?

Is this a California or Federal emissions car? There is a sticker under the hood stating CALIF or FED.

The car will run OK.

If it is carbon, no need to buy parts. The carbon is cleaned out.

 

Thanks for the help everybody. I took it to a shop close by my house. They tested it and said it was the cat...they replaced it and I took it back thru emissions. The readings were before and after: HC-.39/.09 , CO-5.46/.64 , & NOX-2.94/1.31. I'm a little dissapointed that the NOX wasn't lower, but I passed.....

Chris

 

Great, thanks for posting back with the results.

 

What causes High NOX Emissions


Thousands of technicians have faced the challenge of bringing a particularly stubborn application into compliance for NOx emissions. High NOx readings are a clear sign of performance issues somewhere in the system. The question is, where?



Among the potential causes of non-compliant NOx readings are:
Misfire condition
Malfunctioning or improperly adjusted EGR valve
Failed oxygen sensor
Leak in exhaust tubing upstream of converter
Excessive carbon deposits in combustion chamber
Improper spark advance
Blocked coolant passage
Overly lean air-fuel mixture
Damaged cold air duct
Failed or malfunctioning catalytic converter
Corroded or damaged engine sensor electrical connections
Please note that while a failed catalytic converter will contribute to high NOx readings, the failure in itself may have been caused by some other upstream performance problem. In all cases, it is crucial to identify the root cause of the problem before blaming the converter.
Case Study
" I'm working on a 1992 3.1-liter Chevrolet that failed in the test lane. The results were very good for HC and CO—nearly zero—but it failed for NOx. The converter seems to be operating properly and the engine is running okay. What's causing the problem?"
Answer: Because this application, like many others, does not have an EGR adjustment, there's little the technician can do to "tweak" the engine's performance to bring it into compliance. It's clear the engine is running overly lean. A lean engine operating condition produces more NOx than usual, and the lean exhaust chemically interferes with the converter's ability to clean NOx (remember that excess oxygen is good for cleaning HC and CO, but bad for NOx).
There are dozens of potential causes of the high NOx readings, ranging from the relatively easy (detonation or failed oxygen sensor) to the extremely difficult and time-intensive (an improperly signaling MAP sensor). Because the engine is otherwise performing satisfactorily, the least expensive option may be to upgrade to a heavier duty converter such as a CleanAir "Premium" unit featuring increased catalyst for greater efficiency.

 

I have no reason to suspect this, but the way it is, as you still have relatively high NOX readings, cause is likely still there. I am suspicious that shop simply went for quick and easy kill, and - what was it, 300-400 job? - instead of truly trouble shooting and figuring out what exactly is the cause. It might have been a small repair item, not worth their time and effort. Also, now they have you "on the hook" for future repairs.

 

I've had the Camry for 10 yrs now, if I still have it in 2 yrs when I have to take the test again & it fails NOx part, I will have to investigate the EGR system.......it was $273 to R & R the converter.