Also failed emissions and looking for advice... high nox, high HC

I am in CA and bought a mystery non-op 1991 4x4 3VZE for $1000 with 226k miles - so no surprise it didn't pass...

here are the results:
15mph 25mph
CO2 15.2 15.4
O2 0.5 0.3
HC 150 93 (MAX allowed: 121 and 70 respectively)
CO .34 .21 (MAX allowed: .70 and .63 respectively)
NO 848 427 (MAX allowed: 704 and 866 respectively)

After my test:

I went through and ran all the EGR diagnostic tests with the vacuum pump and gauge and everything checked out. Replaced all the EGR vacuum lines anyways and found a crack in the fuel pressure regulator vacuum line. I ran injector cleaner and 91 and drove 360 miles from the bay to southern CA. (Got 21mpg tank average mostly @60mph on 91 and injector cleaner!!!) I haven't tested it since then but I think my exhaust still smells pretty nasty and am hesitant to waste the money on another test.

Here's the rest of the history for the car from before I got it smogged:
Registration is from 2019, Non-op since then.
Had a leaky main seal, replaced.
inspected oil pump, good: replaced o ring and back together with sealant.
Timing belt was 1 tooth off when I got it. fixed.
This made awful predetonation... drove 60 miles back to my house and fixed the iginition timing.
Had to restep the distributer. I think they were making up for the distributor with the timing belt?

Top of the rad comes in just above 200 and the bottom usually read 175ish after 20 minutes of driving.
No CEL
No odd sounds or anything that I can tell.
My dad has a 202k mile pickup with 3vz that I can compare

 

Hi:
Three major items come to my mind regarding high NO, and high HC.
1.) Most common is unmetered air getting into the engine after the AFM causing lean misfire (gasket leak possible, spray carb cleaner around intake manifold & look for a engine idle change)
2.) Second most common is bad ignition components, spark timing, high resistance plug wires, old plugs, base engine timing. (also borrow your dads igniter/coil assembly for an elimination test)
3.) Third consideration is an injector(s) with a too high or low resistance coil, or clogged tip, or a leaky fuel rail. The fuel pressure regulator lives on the rail, don't overlook that guy.
The cold start injector could be adding fuel when it's not supposed to.

Was the timing belt ever changed? Worn cogs, coupled with a faulty belt tensioner could cause it to jump a tooth. I am pretty sure that your tensioner is of the spring type. Later ones are hydraulic.
Your thinking that the P/O slipped the belt one tooth, to make up for an improperly stabbed distributor, is a little out of whack.
The amount of time and labor to do that, is way out of proportion to any benefit, real or imagined.
Has the head gasket ever been changed? The factory gasket has been proven to have a death zone of 180-220 K miles.
Are you losing coolant at all? Even a minor coolant leak into one cylinder can really upset the fuel trim calculation. A cylinder leak down test might be in order.
I live in the SF Bay Area, so I am fully aware of what you are facing.
I went through the same dance as you 12 years ago when I bought my first Runner. It was a bitch.
But once you have all the dominos lined up, it is a good stable engine emission system, that will hold a tune with proper maintenance.
Post results please.
Good Luck.
Art.

 

Ok. I wouldn't put it past the PO with the distributor stuff... Everything he touched was a little out of wack.
Timing belt is new. He did it 5k miles ago. Looked good and tension is good. Cogs look really good. Fairly certain I have no coolant loss.

I forgot that the end cap for the wire that goes into the middle of distributor actually came off. I just crimped it back on with a wrench... I could definitely replace those. Besides that I'm not sure how to tell if a plug wire is bad and I have no clue how old they are.

I'll look into the rest of those things. This has been such a pain I'll be sure to update so others don't need to suffer

 

Art is definitely right about a lean condition and or misfire causing those emission readings. Another thing to consider is the catalytic converter. A quick way to see if it’s ok is to take the temperature of the inlet and outlet. You want the outlet temperature to be at least 20 degrees hotter than the inlet. If the temp is the same or less than a 20 degree split, the catalytic converter is bad. Smack the catalytic with a rubber mallet and see if you can hear anything rattling in there. That’s another sign that it can be bad.

 

Hi:
Borrow, or treat yourself to a cheap Harbor Freight Volt/Ohmeter.
Any excuse to buy another tool.
Measure the resistance in ohms of each of the plug wires, including the center wire back to the coil.
The Toyota manual says no more than 25 K ohms for each wire end to end, regardless of length.
When I measured my wires they averaged 12-15 K ohms each. Wiggle the wire as you measure the resistance to aggrevate any possible internal fracture.
Like the guy upstairs said, beat on the converter with a soft mallet, and listen for crap rattling around, a sure sign the honeycomb assembly has perished.
Wash, Rinse, Repeat.
Post results.
Good Luck.
Art.

 

Sorry to hear of your struggle. I was just there, but on the other end of the emissions spectrum.
Sure sounds like poor ignition, as was already eluded to above. I can definitely vouch for the improvement with new coil, wires, cap and rotor. Probably needs it anyway and fairly cheap, so it doesn't hurt so much.

 

Sorry for the delayed update but I ended up swapping out my cat with my dads OEM one off his 202k mile 93 pickup. Thats all it took. knocked my NOx and HC down to less than 110 ppm. Glad I was able to familiarize myself with the car through all this but man oh man if I had known it was only the cat that was failing me. I dont know what happened between the previous owner replacing the cat and now but it wasn't doing anything it was supposed to be doing I guess.

 

Cool. Pretty easy fix then. A new Cat is all I needed too, except it cost me about $800.

 

I failed today, first time ever . I bought a new cat from eBay and will be sending my original injectors down to LCE for cleaning. I noticed mine has been smelling rich. I replaced the 02 sensor with a Denso OE unit a few weeks ago and noticed no change. The only change to my truck was replacing the original injectors with the 4 hole type. So when the new CAT comes I’ll R&R it and go back for one more try before I send the injectors down. My CAT is the OE and at 30 years might be failing.

This is the first time since 2014 (when I got her) that my 4Runner hasn’t passed with flying colors.

 

bthp223,
You are lucky some a-hole has not pilfered your OEM CAT. They are worth a lot of money for the palladium. Mangna Flow makes a nice CARB legal CAT that is 2-1/2". I'm sure FlowMaster does as well. But you will have to make flanges to get them into the OEM location.