I have been battling with my 1991 4 Runner to get it to pass smog here in CA. It failed HC, CO, and NO at 15 and 25 mph.

Facts:
3VZ-E @ ~170k
Automatic
4x2
235/75/r15 Bridgestone duelers, stock gearing
New plugs - NGK V-Power BKR5EYA
Clean air filter
Clean oil and filter
Does not overheat, no oil in coolant, no coolant in oil. Doesn't burn/leak either of them.
Timing @ 10* set according to FSM
New O2 sensor - Denso 234-4055
No CELs
No vacuum leaks
No visible fluid leaks around the heads, valve covers, or front cover
Great gas mileage; ~16 city/mixed, ~19 hwy
Doesn't feel down on power
Starts on the first crank
Exhaust smells like straight gasoline

Here are the numbers:


Since my gas mileage is nearly stellar I'm almost certain I don't have leaky injectors, fuel dampener, etc. Idle is perfect, no shaking. No hesitation when I step on the gas or work the throttle body; instant power. I recently Sea Foamed it (after failing the test but before changing the O2) and it runs the same and the exhaust still smells heavily of gas.

The only things I haven't replaced are the Cat or anything in the EGR system... and here's why: The EGR controls NO, but my HC and CO are still high. I have read that high HC can create high NO. So where do I start?

From searching it seems like I may need a new Cat, need to test/clean the EGR system, AND possibly replace the charcoal canister. But before I do it all, where would you start and why? Cost isn't a problem but I'd also rather not spend a fortune if I don't have to.

Thanks guys!

 

I just plugged your 25mph numbers into a Lambda calculator, and they come back OK, kind of lean actually.

Lambda: 1.012

If > 1.02 the cat is less effective. Also will be creating more nox from higher combustion temps. The closer to 1.0 even the better.

I bet your exhaust smell is just because the cat isnt working at all, so yours smelling the raw exhaust, kinda like when you smell the exhaust from a class car, burns your eyes a bit? (In a good way of course!) My first guess would be like you already mentioned, replacing the CAT, and see how it goes after that. You mentioned that everything else seems fine, and the engine is in good working order, no power issues or leaks. CAT sounds easy enough and would leave you with this situation. FYI I have read it will take some miles to break in the cat initially, no idea how true that is just thought I would mention it.

 

Thanks mbomberz. Back in the day I built a couple of 400+ AWHP turbo Eclipses/Talons and it does smell like every car I've run without a Cat at the strip, but not quite like our Pike's Peak cars (but I can attribute that to not running a Toluene/Methanol mix in the Runner hahaha).

The Cat is my number one suspect too but I wanted to get a second, third, maybe fourth opinion before I swapped it.

What do the rest of you think?

 

170K isn't much, do you still have your oem cat? or was yours one of the many victims of stolen cats back in the early to mid 90's and now you're running an aftermarket. I still have my oem with over 200K and pass smog fairly easily, but heard the aftermarket ones don't last very long.

 

It's been replaced at some point in time. I'm not sure if it was due to theft or not but it is aftermarket.

A new CARB legal cat is only a little more than ~$200 installed by my exhaust guy. I'll likely drop it off with him tomorrow morning and try to get it tested in the afternoon if it knocks out the smell.

 

Let us know what the result comes back as....aftermarket = suspect.

 

I would agree the most likely candidate is the cat. The effectiveness of the cat makes no difference in how the engine runs, but a lot of difference in cleaning up the last of the emissions (assuming the O2 sensor is keeping the mixture correct)

 

I'll report back for sure, it's not in my nature to leave things unfinished. Not many things bother me more than searching for an answer on a forum and finding an unresolved thread, or 10 unresolved threads on the same topic as it seems to be.

 

when reading the first post, my first guess was the cat. as well.

Just in-case, it could be a good idea to do a diagnostic on the AFM. The AFM do fail although not often.

 

I'd drop money on the converter being bad. If that's not it, the valves should be checked and adjusted before going any further.

 

Thanks for all of the suggestions guys. I went ahead and had a new Cat put in today. My muffler guy said the old one was nothing but honeycomb, no catalyst left at all. The truck runs just as good as before but I can't smell the exhaust at all!

I stopped by my Smog guys' place after putting about 50 miles on the new Cat and he said to try to get ~200-300 miles on it to really get it working before I come back. I'm going to blow through the miles this weekend and have it tested on Monday. I'll report back afterwards.

 

You probably need to clean your plenum. I dont know the 3.0 plenum but the EGR is quite simialr to the 22r EGR. Here is how I have gotten my EGRs working. I know it plays a part in the NO.

I worked on the EGR. Here is another picture that may look like the wrong way to do this, but the screw will strip if you use a screwdriver. Get a good firm grip, but not so hard to distort the screw.


With the screw out, get another bite on the the pipe to get it out of the EGR. Leave the carbon in the pipe at this time as it will help keep the pipe round. The carbon is hard as concrete. Slowly work back and forth to get the pipe spinning inside the EGR tube and to start breaking it free. Could take up to 10 minutes but just be patient.


Once you get the little pipe out, I tap on the the big nut with a wrench to help break the rust up on the threads. The I mount the nut in a vise and tap in both directions, tightening and loosening, with a rubber hammer. I have tried using wrenches and did snap an EGRs threads one time which ruined it. These run about $150 on ebay if I recall right. This could take another 10 minutes.

After it is apart, I use a drill bit, screw driver, nail, clothes hanger to get all of the carbon out. It is rock solid in places. You can put vacuum on the hose and see and hear the plunger moving and operating inside the EGR, the goldish part.


It is clean and working but didnt get any pics. I took a wire brush to the whole EGR and then coated it with WD- for the pretty factor.


I cleaned the valve to the EGR. It is marked on the sides with "Q","R","S" on the brown part as well for correct reposition. The cotton like material is easy to clean, just need to be careful with it. I also got the metal lines that connect to it cleared. One was clogged. The black top just comes straight up to remove. Will need to check the plastic lines are clear as well on it.


This line had a hard clog in it. I took a clothes hanger and air hose to it get it clear. I have fixed several code 71s just by cleaning all of the above and never had one come back yet. The tabs on the bottom willget it back into proper postition.


Here is one of the metal pipes that was clogged. The carbon gets hard as a rock. I use a drill bit with my fingers to help break it loose. The carbon on my finger is only half what came out of the pipe.


This is the same port that was clogged. The rest were clogged just as well. This is normal as to what you are going to find on a 150k mile or more trucks.

 

Terry has this stuff down, I would take a peek at the things he mentioned just to be sure before you get it smoged again. I know the plenum on mine was pretty bad when I did the rebuild on 22re and 2vz-fe (camry).

 

Thanks Terry. I'll go through it all this weekend!

 

Thanks Grego !!!

General Specific... I have not removed a Throttle Body off of a 3.0, but do NOT mess with the TPS, leave it attached to the Thottle Body and dont mess with the adjustments. On a 22re Plenum, I use differnent cleaners but have never tried oven cleaner like some suggest. A wire brush and long screw drivers to use a scraper and loosen the chunks of carbon out of it. I have gotten chunks the size of a quarter and proably a quarte inch thick. Then I take it to a carwash and spray it out. I use a trash bag as a rain coat as it is mess and stains clothes.

Check all hose connections (metal and rubber) for blockage. I am sure most that applies to the 22re motor is quite similar to your motor.

As I understand the EGR introduces hot air into the combustion cycle and warmer air actually is a cooler burn then when cooler air is used, as cooler air is more dense and a hotter burn. Makes sense to me as that is why racers like to have cool air for racing. Just the way I understand it if it makes sense. Somehow this is the purpose of the EGR to bring down your NOX? maybe???

Like others have mentioned, an aftermarket catalytic converter is junk and for California purposes will usually fail smog.

 

The throttle body and plenum are nearly spotless on mine. The whole engine really is a gem and everything comes apart/goes back together without any issues. Just a benefit of good maintenance and a warm dry climate I guess.

You're correct on the EGR function in both theory and practice.

The Cat I had installed yesterday is aftermarket but is also vehicle specific and CARB legal. I have no doubt that it will pass as is, however I am going to open up the EGR as you have suggested and check for any blockages or restrictions.

 

Simple truth: the EGR valve on the 22re will not be called on to operate during the California emissions tests. This means the catalyst is being tested, as well it should be; EGR operation is not a factor, sadly.

 

False, The EGR is active during the 25 mph test.


Also false that the EGR doesn't affect HC, It has everything to do with HC.
EGR opens during cruise and lets inert atmosphere into the intake to cool the burn.
If the EGR is stuck open you will get high HC through out the test and higher on the 25.
If stuck closed you will get higher NO during the 25 mph test.


if his test results varied more for the better on the 25 mph test I would assume the CAT is not getting hot enough to make the burn off or chemical change needed.


You have no change at all and that is a bad CAT or gutted CAT.


Oversize tires on an auto with incorrect gearing will keep and engine loaded on the 25 mph test and the EGR will not activate showing higher NO.

 

I have heard over sized tires will cause an emissions test fail. Forgot about that one. When I had to do smog test in California, they didn't drive them as I am assuming they do now.

Another issue I have heard to fail a test there is headers. I don't have to deal with smog test now so don't know on that one.

I would also suggest doing the Sea Foam treatment thru the intake system before going to the test. I would not suggest running it thru the tank as if you have 20 plus years of varnish build up in the tank, you just pushed it thru the fuel filter and injectors. Not sure what the tanks in California get like, but in the Midwest or humid areas, they get nasty.

 

Terry - I started pulling some of the EGR stuff and it was all spotless (I'm serious when I say this motor is a gem) so I stopped and put it all back together then just drove it for the weekend. I'm not running headers and my 31s aren't going on until the end of this week (though they aren't large enough that I would be worried they would skew the results).

I always run 91 octane in it and I ran a can of Sea Foam in the tank that I burned through this weekend. I had also run 2/3 of a can through the brake booster and PCV the night before I did the Cat.

I took it back to test today and it passed with flying colors. Looks like it was just a dead Cat. Here are the results:



Thank you to all who contributed. There is a lot of good information in this thread. It's all legal now and about to be shipped to Hawaii so when I move at the end of the month I'll meet it there!