Been 3 times for tests and I am going backwards.

12-10-15
Just took it in. Drives great, no smoke, no codes. FAILED

12-16-15
Changed front o2, cleaned MAF, checked for any leaks in air intake boot. a few small cracks were sealed up with electrical tape.

1-6-16
Changed plugs, wires, fuel filter. Seafoam through PCV hose and then again about a week later. A little in the tank, ran through almost all that gas, and then refilled with super Chevron.
FAILED and got WORSE!!!! LOl

WTF

Any ideas? I know that the CAT is my next step but Id rather hear some thoughts before I drop $250 on it

Also, the guy at the test only place is telling me to change out the rear o2 and that would help. I have always understood that the rear o2 isn't doing much and therefore wouldn't help in this case. Any thoughts before I drop another 60 on a new o2 for the rear?

 

Try adding a couple gallons of e85. Will help pass a borderline failing nox vehicle. Your running lean( .00 co )which is causing your cylinder temps to rise which is causing more nox production. Since these motors dont have egr valves its the converters job to reduce these nox gasses. A new factory or factory quality converter will take care of this. It i also being made worse by an old or non factory maf sensor. Anyways adding the e85 in a percentage less than 20% to premium gas will cool your cylinder temps( alcohol cooling effect ). Its a cheap trick i would try before doing a cat. But since you have failed so many times already, another "attempt" might look bad.

 

Also with a scanner monitor fuel trims and see lean you are running. You might have some vacuum leaks you are not seeing. And always always always try and use factory original parts and stay away from aftermarket parts. Espcially when it comes to tune up parts like gaskets, plugs, wires, t-stats... Etc. the original stuff will go ten times longer with no probs. As for aftermarket cats.... They wont last nearly as long as your original factory one. Shops will try and sell you an aftermaket cat. Just be prepared to replace it in a three or four years if that. And maf always factory. It has the single most important job of the entire fule injection system. If it is ten years old. Replace it with a factory brand new one and watch how much better it runs!!

 

I had problems with my EGR system causing high NO. Vacuum hose routing was mixed up. Check the routing carefully as its easy to mix up. Also look at condition of vacuum hoses and make sure they hold vacuum pressure or they are not clogged.

Take off the EGR and inspect where the small hard line tube.... see photos.









Mine was completely plugged with carbon deposits. The deposits are hard and crusty so devise some way of mechanically scraping. A drill bit and some welding wire worked well for me.

 

I wasnt aware 3.4l v6 cali cars had egr valves.........?

 

Some of the early Tacomas had EGR but that was dependent on model (single cabs did, extended cabs didn't; or something like that), the 4Rnners with a 3.4 never had an EGR system, and I'm not sure about T100s or Tundras).

 

My Bad, I saw 1992 Toyota Pickup Ex-Cab but missed the 3.4 swap part. I was referring to my 1985 & 1986 Truck and 4 Runner 22RE.

 

Frustrated!!!!

Changed the rear o2 sensor to another NEW Denso, replaced the CAT with an Easton brand new unit.

Took it back in today and again........its gotten worse. WTF

Didnt try to E85 as I figured the new CAT would solve it with the new rear o2 being a bit of overkill.

Other than a new MAF, I cannot think of where to go from here.

Smog guy did feel sorry for me and didn't charge me, so that was good. LOL

 

Also, this isn't one of my swap vehicles.

This is a 98 tacoma, auto ,4x4 daily driver.

 

This has been a nightmare!!

I have been noticing that the idle was a bit rough so after chasing vacuum leaks on split hoses with the help of a friend with a smoke machine, the slight rough idle was still there.

Decided to pull back the cover and take a peek at the timing belt.

Holy Captain Worn the Heck Out!!!!

I am hoping that this gets me back in time and makes the lean burning go away and it will finally pass smog. Pained to think that I have replaced the plugs, wires, fuel filter, both O2 sensors, the CAT, and spend many hours chasing down culprits.

Oh well.......I just want it to pass at this point.

 

Thought I would update this for future searchers for similar problems

After changing out the wires, plugs, fuel filter, CAT, both O2 sensors, seafoaming this intake.....twice. It turns out the culprit the whole time could have been the timing. Who knows if any of the other items I changed contributed to it passing along with the timing belt but I dont care cause it passed today.

So if you have this high NO problem, check your timing.

 

Looks like it BARELY passed. You were at the max for HC !!