Toyota Avalon Failed Smog for High NO Emissions

I recently changed the Bank 1 Sensor 1 Oxygen Sensor on my 1997 Toyota Avalon, which has about 40,000 miles. I applied the anti-seize lubricant that came with the Denso 234-4622 O2 Sensor.

The MIL went off after 14 miles, but the car failed the Calif. NO test as follows: 15 mph - 889, 25 mph - 1183. The rest of the scores were very good, very low. I then drove it 140 highway miles. Turned off the DTC code in memory. Drove it another 70 miles around town with little NO improvement on a retest as follows: 15 mph – 852, 25 mph - 1139.

There are no other DTCs except that for some reason (?) the “EVA” cycle has not yet run.

Questions:

1. Could excess anti-seize lubricant squeezed out, and sitting in the airflow stream raise NO?

2. Could the “EVA” failure to cycle be a clue as to what might be going on?

3. If not 1 and 2 what else might be the problem?

4. What if anything can I do to correct the problem, whether excess anti-seize or your other thoughts? For instance, if it’s possibly excess carbon buildup, is there an additive that I might add to clean that out?

Answer:

The likelihood of the anti-seize lubricant causing your Toyota Avalon to produce high NO is slim to non. Unless the lubricant (in large amount) seeped into the oxygen sensor (and began causing the sensor to send out lean fuel voltage), your Avalon's high NO fault is not due to the lubricant.

We'd recommend looking into other faults, beginning with air/fuel mixture. It is very important that your Toyota Avalon is not running lean, and that its EGR system is functioning properly. These are the two main reasons vehicles produce high NO; not enough fuel and not enough EGR (exhaust gas recirculation) flow.

Any problem which would cause a lean fuel condition will raise NO emissions. You have to check for simply things such as vacuum leaks, all the way through emission components responsible for measuring intake air flow, such as the mass air flow sensor (MAF).

What Causes High NO?

posted by SmogTips Support