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Failed Smog need help!!

25K views 80 replies 20 participants last post by  4wd_mofo 
#1 ·
Well the 99 4x4 V6 taco went in today to get smoged. CO2 is fine, HC and CO fine, it's the damn NO (PPM) whatever the frunk that means. I live in California and they are strict as a MOFO on in this bitch. Max value at 15mph is 512 and i ran a 685. Realized that i had the deck plate mod open, and closed it up to make it stock again. put some 91 octane in, ran it hard for about 60 miles then came back. Second go dropped from 685 down to 601.

The truck is stock, outside a K&N drop in and deck-plate mod, and 2.5" cat back piping with flow-master muffler. This bastard passed 2 years ago no problem. It's Got 197K miles on it, I've had it for 4 years, and put 54K miles on it. Only thing i can think of is to swap out the O2 sensors. IIRC there are only 2, one in front of the cat, one behind. Any help would be great, thanks!
 
#2 ·
NO is nitrous oxide.

Do you have a check engine light on?

Vacuum leak?

Clean MAF?

Do you cats rattle when hit(loose material inside)?

Bad O2 sensor?

Maybe Seafoam it.
 
#4 ·
i changed the plugs and wires at 180k, should be fine. The cat hasn't even been on the truck for almost 2 years. i put it back on a month ago so the ECU would work with the O2 sensors to remember what a cat is like. No CEL, no codes, no leaks. Sense the other read outs on the smog are good the only thing i can see would be a problem with be a leak, or the sensors. it's $53 each on amazon.com right now, for replacement Denso o2's. gonna order them up and see how it turns out.
 
#3 ·
High NOx readings are usually caused by high combustion temps and or a failing cat. One of the functions of the cat is to reduce the NOx levels. Assuming your cat is good due to the other readings and the comment about your deck plate, I'd look at a possible issue with the EGR not functioning correctly or the fuel mix is too lean.

Clean the MAF if you haven't already. You can buy specific MAF cleaner spray at the autoparts stores. NEVER touch the sensor element, just dowse it with cleaner and let it air dry. Next, check to be sure the EGR is opening and closing by drawing a vacuum on the top port. If you reach under the EGR (when cold), you should feel the diaphragm retract.

If you have never replaced the front O2 sensor, then it is due. They are only rated for about 100k miles of use anyways. www.sparkplugs.com has good prices on Denso OEM replacements or you can get factory OEM from www.toyotapartsales.com

Also, if you haven't done a tune-up recently, do that. Just changing the spark plugs and the oil has a noticeable effect on the smog performance. Make it a habit to do a tune-up and oil change before you get a smog check. You'll have far less issues. Don't forget to change the PCV valve also.

If none of that helps, then its probably time for a new cat. You can always inspect it with a flashlight to see if the honeycomb is largely intact with no deep holes.
 
#5 ·
yea, been running Royal purple since 155K miles, that was recently done. The cat is fine, when i pulled it 2 years ago it looked fine, and it just sat in the garage, doubt it went bad. I didn't even know we has PCV's on these. never even looked. I have cleaned the Throttle body 2 times, and never the MAF, and never the O2's. the stupid kid i bought the truck from with 144K miles took it to a shop that changed on only one side of the block (the easy side) spark plugs. So i change them every 30K. Should go get a PCV and check the EGR.O2's wouldn't hurt, been debating doing them cuz my MPG have been slowly getting worse.

thanks for the link but Amazon's got you beat :p

http://www.amazon.com/Denso-234-416...otive&Make=Toyota|76&Year=1999|1999&carId=001
 
#15 ·
you can verify if you have an EGR system by looking at the emissions sticker under the hood. All California emissions vehicles will have an EGR.

The EGR is a valve with a round metal cap on it near the back of the engine. On the top, there is a vacuum line that goes to the center of the cap. This opens and closes the EGR valve. Using either a vacuum gauge or just some kind of vacuum pump, draw a vacuum on that line to make sure the EGR opens and closes.
 
#16 · (Edited)
very true, I live in CA, and that is where the truck is from. It has an EGR, I can clearly see it. I just sold my MR2 spyder yesterday, so i got $$ now and will be buying 2 new O2 Sensors. I'll let you know the outcome of the newest smog when i take it next week. I believe the O2 sensors are the originals, due to the lack of maintenance before i bought the truck with 144K miles.

P.S. how was big bear? if my lift and tires where installed i would have gone but i needed to sell the car first for the new rear suspension...
 
#19 ·
I would replace your front O2 sensor. I had the same issue with high Nox and 200K in mileage.
 
#20 ·
they are only $53 on amazon including shipping. Im going to do both, do you know if the front one is different from the rear one? gotta find some time to get under the taco when it's under 100 degrees outside...
 
#21 ·
Don't know about your year but CA emissions vehicles are different and I believe at one point they all switched. Front O2 was replaced with A/F sensor.

I have a 2000 taco CA emission spec. The front sensor is an Air/Fuel and the rear is an O2. 250$ for the front and 100$ for the rear.
 
#22 ·
Don't know about your year but CA emissions vehicles are different and I believe at one point they all switched. Front O2 was replaced with A/F sensor.

I have a 2000 taco CA emission spec. The front sensor is an Air/Fuel and the rear is an O2. 250$ for the front and 100$ for the rear.
how can i tell if it's a Air/Fuel vs. O2. And my understanding is that any O2 is an Air/Fuel...
 
#23 ·
I went through www.sparkplugs.com that Showstop mentioned above. I called them for my truck since Denso had several different part numbers. Based on their website and your truck their are 3 different part numbers for the front and 4 for the back. They all say 02 sensor. When I bought mine the different part numbers were related to the length of the electrical wire. I measured the electrical wire and called in the measurement. www.sparkplugs.com matched it up and It was delivered in two days. I believe they came out of Corona so you being in Diamond Bar might be one day delivery.
 
#24 ·
oh thank god. I just looked at the o2's on my taco, the part numbers do not match the ones on Amazon.com. However, the ones on sparkplugs.com do match up with the ones on Amazon. i see there are 4 wires coming out of each O2. I guess i'll measure then order both.
 
#25 ·
Now here's the kicker, a month ago my numbers for the NO(PPM)
15mph test=685 Max allowed is 512
25mph test=479 Max allowed is 765

So i plugged up the Deck plate mod, put the truck back to stock minus the K&N drop in filter, and the flowblaster exhaust. Ran $15 worth of 91 octane and drove the truck hard for a day. Returned the next day and got these numbers
15mph test=601 Max allowed is 512
25mph test=505 Max allowed is 765

So again i failed the second test. got the new O2's in, a new vac line and PCV valve, runs great, no CEL and my MPG seems to be a little better. Drove for about 4 days after i replaced them and reset the ECU (unplugged the neg on the bat). I got to another Smog only station (just incase the one i was at wasn't working correctly) and i get these numbers

15mph test=676 Max allowed is 512
25mph test=540 Max allowed is 765

WTF?!?! it got worse after i replaced the O2's! :doh: So now, i'm going to change out the spark plugs (even tho there is only 14-16K on the ones in there now) And run a can of sea foam thru the Brake vac line into the intake manifold and some in the tank. Maybe run some 91 octane again, seemed to help. I'm out of ideas, need to get this smogged asap. The worst thing is, i found my smog report from 09, about 19K miles ago, I got these numbers...

15mph test=142 Max allowed is 512 :eek:
25mph test=8 Max allowed is 765:eek:
 
#27 ·
You had 600+NO(PPM) readings? where were they? I got a can of MAF cleaner, going to do that and the SeaFoam tomorrow. How do i clean the EGR? take all the hoses off and blow it out with my compressor?
 
#30 ·
NOx is caused by high combustion temperatures:

The egr releases exhaust back onto the intake, and displaces the amount of combustible matter in the cylinders.Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates.

The EGR is either clogged (passage between the valve and intake)
or the Vacuum system is not working properly.

easy way to test EGR valve, is to pull a vacuum line on the intake, and use it directly on the EGR valve, the engine should run rough or stall out.

The other three components to check for the EGR system, are the EGR vacuum modulaor, the Vaccum switching valve, and the Engine Computer.
 
#31 · (Edited)
technically if what your saying is true "lower temps caused by EGR" couldn't i remove the EGR and fix the high temps caused by it?:D. I've removed an EGR from a mr2 turbo like 2 times, but i can't seem to find this one on the truck, have to wait 20 mins for it to cool down, i just cleaned the MAF, Cleaned the TB, and seafoamed the hell outa it.

Is this the EGR? looks like a FPR to me...
 
#37 ·
So i took it in only to fail smog for the 4th time! :xcrybaby:
I've done the following now...

Spark plugs
new O2's
dusted off the K&N drop in filter
cleaned the MAF
oil change
new PCV valve and line
ran about 3/5 of a can of Sea foam thru the motor, then the rest in the tank

I get perfect numbers for the HC and the CO, but the NO(PPM) is 552 at 15mph and the max allowed is 512. She is at 479 at 25mph test and max is 765 so that passes... can't figure out for the life of me what's going on. I can't seem to locate the EGR, and i keep getting 40% of the people saying they don't have one, and 60% saying it's there, however i don't see it unless it's hiding:confused:.
 
#38 ·
I failed my NO test, too - spec here in Az says 3.0, mine was at 7. Had the front 02 sensor, cracked K&N FIPK pipe replaced, cleaned MAF. That got it down to a 3.19 so I'm close..
I have Seafoam in the tank and am going to replace the PCV valve, plugs/wires. IF that fails I'll do the cat...

BTW, why have people suggested running High Octane Gas to help with the test ?
 
#49 ·
I passed smog today!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

its sad that when you live in Cali, and you pass smog it feels like you won the lottery :xcrazy:

So basically i squeaked by, but what helped the most was the fact that i did a synth oil change 1 hour prior to the oil change, ran a stock air filter (took out my K&N drop in) and Showstop showed me how to properly clean the maf by taking it out all the way. Im wondering if anyone has done a write up with pics/info about what it takes to pass smog in Cali, or any other state that has emissions. I'm going to be working on my recently purchased 01 4x4 V6 TRD toy, maybe i should snap pics and do a How to for everyone.
 
#52 ·
I finally passed smog today also, and yes I feel as though I won the lottery.

Took me several seafoam treatments new NGK plugs, coilpacks/wires/, air filter, fuel filter, oil change/filter, o2 sensor...
I was struggling with the NOx. Finally squeaked by....512 max, with 509 measured on the 15mph test. Everything else was ok
 
#51 ·
yea well i couldnt have done it without you bro. got my new 01 rig, starting to plan out what im doing to her, and getting it set for being a street queen for a bit with the best mpg i can :D
 
#55 ·
I am in the same boat as you were. What sucks is I passed emissions my first time through, failed visual due to gas cap. Retested the same day, and got 4ppm over max on NO @ 15mph....

This was after already doing a full tune up/timing belt/water pump etc.

Im glad I dont have an egr valve cause i didnt want to clean it! And the other fixes seem much easier to do (seafoam/MAF cleaner). Im thinking ill flush the coolant too.

Just realized how old this thread was... at least it wasnt 4 years old though!
 
#57 ·
Well I'm reviving this thread...

My wife's 1999 3.4L Taco failed CA smog last weekend with issues just like those above. Every thing passed at or below the average except for the 15 mph NOx was almost double the allowable. The cat is 3 years old as it was stolen from our house by some tweakers.

I was reading online and found the EGR to be the best place to start for high NOx readings. After reading this thread I realized the 3.4L doesn't have one. I checked my 04 Tacoma and couldn't find one. Last night I ran to the parts store to get some stuff as listed above to start working on her car, and sure enough she has an EGR sitting behind the throttle body. When did Toyota stop putting EGR valves in the 3.4L?

Anyway's I'm going to do the stuff above and see if I can bring the 15 mph NOx values down. Also plan on cleaning the EGR, changing the fuel filter, and using a can of "CRC Product Guaranteed to Pass Smog".

I wish I could afford to use the can of CRC and see if it passes with just that.
 
#59 ·
When did Toyota stop putting EGR valves in the 3.4L
The newer the engine the more chance of EGR systems... I know when I swapped in my "new" 3.4 out of a 98 T100 in my Taco (check sig for details) that the T100 engine did NOT have EGR and even had block of plates and I shoulda left them on instead of putting my EGR system on since it's fucked anyway.

EGR=JUNK

Ditch that shit if you can, I plan to move out of the state I'm in within the next few years though so I'm probably gonna have to fix mine instead of yanking it off (which I would like to). I've always had the mentality that if a 1968 Mustang GT didn't have it's got no place on my ride... But I'm old school. :2cents:
 
#60 ·
FWIW, did you guys replace the gaskets when you removed the cat converters?

Exhaust leaks before the cats can introduce air and cool the gases, making it too cool for the cat converter to do its job.

You could also be too lean, which is raising the combustion temps. Make sure the filter/MAF/TB is clean. Make sure there are no cracks in any vac hoses. You may want to opt to change your intake gaskets. Overkill, but what about the fuel filter?

Low coolant level or too much antifreeze to water ratio, can lead to higher cylinder temps. Because I don't freeze where I'm at, I run a 60% water, 40% antifreeze mix, with Redline Water Wetter. The fan clutch could be at fault also. Test by crumpling a newspaper and sticking it in the fan while the motor is idling. If the fan stops, the clutch is bad. If it's good, it will shred the paper.

Running higher octane won't make it run better. All higher octane does is prevent pre detonation. There is absolutely no point in running higher octane to pass a test.

Also overkill, a lot of shops do not set up the fan in front of the motor. Insist that the fan is setup and running. Without the fan, temps could rise because of less air passing through. The dyno test is supposed to simulate driving on the road, so you should have a fan pushing air, like it would be on the road...
 
#63 ·
Pulled apart the intake and throttle body last night, everything internally looked extremely freaking clean (180K miles). Just a very little carbon build up on the throttle body. The EGR valve looked brand new. Pulled the plugs they all look great, and are gapped at 0.44. All the vacuum lines look to be in great condition and connected securely to their connections.

The PCV looks like it could be replaced. To remove the PCV do you just pull up and out of the valve cover. Is there a trick? If so I guess I need to go get my man pants out of the closet.

The air filter was surprisingly dirty, so I replaced that. And cleaned the MAF. I'm hoping that was part of the issue. Although I thought running lean makes for more NOx, and i would think with a dirty restrictive air filter I'd be running rich.

I guess tonight I will change the fuel filter, and run a tank with the "CRC Pass or Your Money Back" junk in it and hope the NOx comes down.

I really don't want to put a bunch of $$ into her truck, as we plan on selling both our trucks in the near future. Future planning for a family wagon (3/4 diesel).
 
#64 ·
PCV pulls right out, don't worry. I'd replace that shitty rubber grommet too, mine was toasted at 295,XXX. I'd be more trusting toward Seafoam than CRC.. FYI, there's not really a way to tell if the "egr looks clean" because most of the time that junk shit ain't. Hope you get 'er runnin clean for the fuckin' NAZI'S! :lmao:
 
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