My car failed smog this morning. I dont get it, it has been well taken care of. Here are my numbers:

...........______HC______ ______CO______ ______NO______
..........Max | AVE | Meas| Max | AVE | Meas | Max | AVE | Meas
15mph 50 | 8 | 2 | .64 | 0.02 | 0.00 | 508 | 88 | 653 FAIL
25mph 34 | 6 | 2 | .78 | 0.02 | 0.00 | 761 | 82 | 477 PASS

I only failed at 15 mph. The shop told me it would cost $95 just to diagnose the problem.

Anyone know what these numbers mean, and if there is somehting I can do myself to pass smog in California?

Thanks in Advance

 

NOX failure is caused by excessive combustion chamber temps. It could be a number of things:

An inoperative EGR system.

Advanced ignition timing (computer controlled on the 5VZ).

Overheating.

Lean air/fuel mixture (got any mods?).

Compression too high due to carbon build-up on the pistons.

If you still can't figure it out, a cooler thermostat will help. But I would try to get to the root cause before putting a bandaid on the problem.

Good luck!

 

unfortunately, i am no mechanic, and am unable to diagnose any of the things below. i read in another thread, that it could be as simple as changing the O2 sensor??

 

It could be that too. Your best bet is to have it diagnosed by someone you trust vs. throwing parts at it.

 

It is running lean. You do not have an EGR system.

Find a shop that offers the Snap On Motor Vac service. This runs your engine on a special cleaner fluid instead of gas and it cleans the injectors restoring full flow, cleans the intake valves, and removes the carbon from the cumbustion chamber.

Then I would install a new front O2 sensor if you have not already done it and finally if you have been running one of those crappy K&N filters clean the MAF sensor.

Then you should pass that test with flying colors.

Gadget

 

You might want to read this for a few clues to what is going on:
http://www.autoshop101.com/forms/h56.pdf

As Christian mentioned there are a few reasons for NOX:

High levels of NOx can be caused by excessive temperature in the combustion chamber of a damaged catalytic converter (I doubt that it is the converter causing your problem....replacing it will make it worse).

Check for problems with the following:
- Air injection system
- EGR system (don't have one on 3.4L)
- Combustion chamber deposits
- Dirty fuel injectors"

You also do well to follow the FSM for complete diagnosis of this problem.

 

I thought some CA vehicles had EGR? Why did my stock manifold have a block off-plate on the drivers side?

Just curious.

 

Tacomas had EGR, the 3rd gen 4Runner with the 3.4 never had it. Remember they put that engine in all the trucks.

Gadget

 

Any idea the rationalle behind not having one on an engine?
I would be interested if you had any insight on this.

 

I failed NOX on my 88 the first time around. Truck was sitting for 2 weeks and only drove it a mile or so to the testing station. The testing guys told me to take it for an hour drive and come back. I did that, and it then passed the 2nd time around.

If testing is free if you fail, give that a shot.

 

Thats actually good advice. I lliterally drove 3 blocks from an overnight stop. Good stuff guys, keep it coming.

 

oh she was running rich.....lol.

 

Would it be safe to assume that if I drove it around for about an hour or so on saturday, then took it to a different smog place, that I would pass??

 

No, I doubt it.
That is usually if you fail for HCs (ie you are running rich) because the cat has not gotten to proper temp.
Yours is running lean already so the cat is plenty hot at that point.

 

Interesting. So they must have decided a block-off plate was cheaper than re-doing the casting process.

Weird. Thanks for pointing that out.

But wait a minute. My 98 Taco had the block-off plate too...

 

This guy says he tested the EGR on a 1998 Tacoma:
http://www.los-gatos.ca.us/davidbu/toyota.html

 

Well I totally believe Gadget; he would know. But I am just curious if it was only on some Taco's and not on all 4Runners...or what?

Doesn't really matter. It's mainly because I am curious.

While we're at it, I wouldn't mind the Taco's "extra" 7 horses.

 

My 96 failed the same thing, it was the catalytic converter and the o2 sensor... did the trick.

 

I am going to get it checked out by a friends mechanic this wknd. I already have the O2 Sensor link. Does anyone know a good online source for Catalytic Converters?

 

Have your converter tested first before replacing, it is much more likely that a bad O2 sensor, dirty MAF or carbon deposits are causing the high NOX problem (as Gadget, Christian and I mentioned). As I mentioned, in most cases replacing it makes it worse. Most people don't understand how a cat works and they think it magically makes all the emissions come out nice and clean so if something is off then the cat must be bad....not so in most cases.