1998 Toyota Tacoma 3.4L Failed CA Smog Test. High NOx at 15mph any ideas of the problem?

Replaced spark plugs 10k miles ago

Cleaned the mass airflow sensor

Replaced the oil filter

Replaced engine air filter

Replaced fuel filter

Seafoamed the vacuum line

Got the cat hot before the test, put in premium chevron w/ techron gas. This is my second test and numbers remain unchanged. Could it be something as simple as PCV valve? I noticed my car has been leaking oil slowly from the backside of the engine, I was reading that a bad PCV valve could cause increased engine pressure and cause oil leaks and high NOx.

Would like any second opinions, mechanic said replace the catalytic converter but there is no promise that will fix these numbers. From what I read online is that if the cat is failing all the emissions would be high, not just NOx at 15mph. This car doesn't have an EGR valve. Gonna bring it in again to have mechanic check the timing, for any vacuum hose leaks. Is there anything else I should bring up to the mechanic to check for?

Thank You

 

Leave California. Fixed.

 

change spark plugs if it has been a while, use lower octane gas (not higher), and thicker oil

https://axleaddict.com/auto-repair/How-to-Pass-a-Smog-Test

 

High oxides of nitrogen can be caused by high combustion temp's. Is your EGR system functioning?

 

There is no EGR system on the 3.4L tacomas. In the report you can see EGR Visual is not applicable

 

You have a Cabin Air Filter but no EGR?
Are you sure you have a Tacoma?

 

I thought it was called cabin air filter, maybe its called engine air filter? Its in the air cleaner box under the hood pardon my ill knowledge, just started learning due to smog issues

 

Ask mechanic to check cam sensor

 

thanks

 

as was stated in the other high NOx thread... NOx is the result of high combustion temperatures and it is the job of the catalytic convertor(s) to convert NOx to other gases. If your truck has an EGR valve that could be an issue. The other ways to modify high exhaust temps are by fidling with the ignition timing and modifying the air/fuel ratio but on most Tacomas these things can be adjusted. If you have an EGR'd Tacoma, exhaust gas is passed back into the intake manifold to reduce the amount of air/fuel to lower the combustion temperature. The "other" way is to put an additive into the fuel tank... ISO-Heat is one product. Iso-heat is an isoprophly alchohl based additive. The thought is... alchohol burns cooler and that lowers the combustion temerature. Will it be enought to solve your issue, I dont know, you are so close that it just might. Then that brings up the question, is this what you are going to have to do every 2 years?

 

It's worth double checking this. It seems like the majority of Tacomas do not have them (Federal emissions package) but California emissions package do. @1997tacomav6 has one on his truck IIRC

 

It also says Fuel Cap Visual is not applicable. I guess you're going to tell us your truck doesn't have a fuel cap either???

 

yes, there is... just kind of rare...

https://toyotaparts.mcgeorgetoyota..../emission-system-cat/emission-components-scat

 

Thanks for the explanation, got any idea of the ratio I should add ISO-Heet to help my NOx numbers? I will also ask my mechanic about the ignition timing.

 

My car doesn't have one, I've checked and 2 other people have verified. This car was purchased in Hawaii, interesting that CA models would be the only one to have them.

 

If the truck like mine was built in California it came with an EGR system.
California emissions have always been tougher than any state even back in the 90s.
You can lookup where the truck was built online with your vin number.
If built in California it came with one.

The EGR system can be deleted easily but that will make the truck fail inspection.

If I could delete mine I would

 

You can also look at the emission sticker under the hood. It will list all the emission equipment.

 

Can you post up a picture of the under hood emissions label?

 

This is what came on my truck with EGR,.
A sticker and vacuum diagram

 

Weird it looks like a Non-CA vehicle but had EGR? Is that because it’s a 97?