I have an 01 3.4l 4x4 Tacoma. It will not pass CA smog for the life of me.

It passed last time barely. This time it will not pass. It is giving high CO and high HCs.

It is not showing any codes. I have tried new plugs and a new o2 sensor, and even new cats. The MAF is clean as well as the throttle body.

It does not give consistent readings on smog. A mechanic tried several things and run several pre-tests and we can't get it to pass.

Anybody have any ideas??

Would the TPS throw a code? What about the fuel pump?

I am thinking it is running rich but I cannot figure out why. Air filter is clean.

 

Find an address in a city in california that is smog exempt, change ur physical address to that one with dmv, and make ur mailing address whereever u want it to be.... Wallah...no smog problems

 

Try running a hotter thermostat. That might lean it up a bit.

 

what do the plugs look like? Does it fail at idle or at cruise? maybe you need a motorvac treatment done to clean the internals. Does it have egr?

 

Did you change the O2 sensor (after the CAT) or the Air/Fuel sensor (before the CATS).


FOG

 

I have changed the o2 sensor, MAF sensor, and air/fuel ratio sensor.

Now it still runs high on CO.

Could it be a leaky fuel injector? Would this throw a code?

Why is it running rich and no code??????

I would like to get it fixed properly.

 

From a 5vz-fe FSM:

CO: Normal HC: High Symptom: Rough idle
1. Faulty ignitions:
• Incorrect timing
• Fouled. shorted or improperly gapped plugs
• Open or crossed high-tension cords
2. Incorrect valve clearance
3. w/ EGR:
Leaky EGR valve
4. Leaky intake and exhaust valves
5. Leaky cylinder

CO: Low HC: High Symptom: Rough idle (Fluctuating HC reading)
1. Vacuum leaks:
• PCV hose
• w/ EGR:
EGR valve
• Intake manifold
• Air intake chamber
• Intake air connector
• Throttle body
• lAC valve
• Brake booster line
2. Lean mixture causing misfire

CO: High HC: High Symptom: Rough idle (Black smoke from exhaust)
1. Restricted air filter
2. Plugged PCV valve
3. Faulty SFI systems:
• Faulty fuel pressure regulator
• Clogged fuel return line
• Defective ECT sensor
• Faulty ECM
• Faulty injector
• Faulty throttle position sensor
• Faulty MAF meter

 

It idles fine.... Not really rough.

The fuel trims appear fine, but could it still be the fuel pressure regulator or an injector?

 

A way to beat the Smog Nazis sounds fishy but works. Use in quart of 93% Alcohol with a quarter tank of 93 octane. The alcohol burns very hot and clean and you will pass. It doesn't hurt the motor and after you pass add more gas to dilute whatever is left.

 

Want to fix the problem not put a bandaid over it. It should pass.

 

Seafoam. Works every time.

Also you said you replaced the o2 sensor. Why not both o2 sensors?

 

He said he replaced the O2 sensor and the air/fuel sensor. On an '01, the front sensor is a wideband A/F sensor, not a standard O2 sensor, so he only has one.