Help: 97 Failed Smog due to high NOx at 15mph, now what?

[calnhob]

So I had to take my truck in for SMOG testing on NYE.

Came back with a failed test due to high NO reading at 15 mph. MAX is 512 PPM and my reading was 566 PPM. NO reading at 25mph wasn't great but was below the MAX at 555.

It's 97 with 229K. No issues, runs great with decent gas mileage. Wires, spark plugs, air filter have been replaced within the last year.

It passed smog two years ago when I bought it but the NO reading was at 485 so a little high but still below the MAX.

Based on some old threads I've read it seems like the best option is to get the CAT replaced. The current one is an aftermarket Magnaflow 445105 that's probably been on for more than 50K.

Anyone have first hand experience with a similar issue? Replacing the CAT isn't too bad, $180 for the same aftermarket Magnaflow + $60 for someone to cut/weld it on but wanted to make sure I'm not missing anything.
Thanks


UPDATE: 1/19/19 - took the retest and it passed. Post here

 

[fixxor]

Do you have long crank start issues?

 

[Nate_GB]

So I had to take my truck in for SMOG testing on NYE.

Came back with a failed test due to high NO reading at 15 mph. MAX is 512 PPM and my reading was 566 PPM. NO reading at 25mph wasn't great but was below the MAX at 555.

It's 97 with 229K. No issues, runs great with decent gas mileage. Wires, spark plugs, air filter have been replaced within the last year.

It passed smog two years ago when I bought it but the NO reading was at 485 so a little high but still below the MAX.

Based on some old threads I've read it seems like the best option is to get the CAT replaced. The current one is an aftermarket Magnaflow 445105 that's probably been on for more than 50K.

Anyone have first hand experience with a similar issue? Replacing the CAT isn't too bad, $180 for the same aftermarket Magnaflow + $60 for someone to cut/weld it on but wanted to make sure I'm not missing anything.
Thanks

You barely missed passing. Did it sit and cool down for a bit right before the test? Did you have a long drive to get to the test center? Catalytic converters perform better the hotter they are. If it was me, I'd retest and see if you can get the truck up to temp and hot lap around the block a few times to get the cats nice and hot and then have them test it right away and I'll bet you pass.

 

[gamefreakgc]

My 4Runner almost failed 2 years ago and I had to test it again this year. I used this product: https://shop.advanceautoparts.com/p...2WxV-bYjcOsCWHi8Kh4aAi_VEALw_wcB&gclsrc=aw.ds. It passed with flying colors. It's worth a try for sure, beats $240+ for a new cat.

 

[calnhob]

I wouldn't say it's super long but it takes a sec to get the car started. I just replaced the starter contacts so I know it's not that issue.
[MENTION=147152]Nate_GB[/MENTION] - I did drive it around before going to the test station. I was about 10-15min but i do wish I had driven it longer and used higher octane fuel.
[MENTION=115347]gamefreakgc[/MENTION] - I read about that and might try it the next time. I don't know if I want to spend the $$ on the retest without getting the issue fixed. The CRC might just be a bandaid for a bigger issue. Did you have high NOx issues?

 

[pluton]

I did drive it around before going to the test station. I was about 10-15min but i do wish I had driven it longer and used higher octane fuel.

My best amateur understanding of what to do prior to a smog test:
Use regular gas, and drive it a good hour (or more) at highway speeds before the test. Take a nice, long drive.
Some aftermarket cats don't last.
Best to find a shop with an exhaust gas analyzer that can check the exhaust before taking it to the official smog shop.
Next best: some smog shops offer a 'pre test' that is the regular test but "off the record" as far as the authorities are concerned.
When I was worried mine wouldn't pass, my shop did the pretest, and then waived the fee for the pretest when I went ahead and got the official smog test right after. Good luck, and may the smog gods smile upon you.

 

[DaMonkey]

Possible cat went bad after 50k. But you are real close on passing so couple things to consider.

Failed NOx = high combustion temps.

Have you cleaned MAF? If not, my bet is that. Poor fuel mixture.

Or carbon deposits. Give your intake a long slow drink of water while revving a hot engine and then blow it out with a couple WOT blasts. Steam cleans your your combustion chamber.

Less likely but worth doing is brushing its teeth. Get a can of throttle body cleaner and clean up deposits in and around the butterfly.

You were real close to pass. Even if your car is starting to go bad, if you have not done these things for awhile it’s a good idea and they will likely push you into pass.

Big bucks no whammies.

 

[DaMonkey]

Forward o2 sensor also. If no history on that, I’d swap it before the cat.

 

[gamefreakgc]

I wouldn't say it's super long but it takes a sec to get the car started. I just replaced the starter contacts so I know it's not that issue.

[MENTION=147152]Nate_GB[/MENTION] - I did drive it around before going to the test station. I was about 10-15min but i do wish I had driven it longer and used higher octane fuel.

[MENTION=115347]gamefreakgc[/MENTION] - I read about that and might try it the next time. I don't know if I want to spend the $$ on the retest without getting the issue fixed. The CRC might just be a bandaid for a bigger issue. Did you have high NOx issues?

Yes high NOx and high HC as well. Heck, all my readings were bad. The tech told me I'd most likely fail the next text and the converter was failing over time. I used the product linked above and my NOx went to the 200's and my HC's into the 20's. Made a huge difference. Just follow the directions on the bottle, you have to run the whole tank through before the test. They even offer a guarentee and will refund the price if you don't pass and have to repair it lol!

 

[nissanh]

Try Eastern Catalytics. They have bolt on type CATS for a decent price.

 

[Wedgy]

I had the same thing, missed NOX by 7...tech told me to run some B&G system cleaner, change upstream sensor, clean the MAF, and run premium gas. Did that and brought it in hot and passed by -26, not sure what did the trick but one or all of them combined.

 

[StreetCreeper]

I’ve been here and done this —> Smog Gods: One man's journey into the smoggy abyss. ( How to lower NOx )

 

[Twisted Sid]

I would try sea foaming the intake side of the engine and then also run some in the fuel to help clean out the injectors to help clean out carbon deposits and then do an oil change and try the test again.
High NO is from high combustion temps. Carbon build up on the pistons can help cause that.

 

[octanejunkie]

Mine passed with flying colors. The Smog Tech said he never saw numbers like mine on a 20 year old vehicle.

Don't waste your time or money on that Guaranteed to Pass crap, it's just ethyl alcohol - you can get more benefit by dumping a bottle of octaneboost in your tank and drive it like you stole it before the test - but the key is to bring it in warm to hot

As far as the other suggestions, they are all good. I'm pretty sure one of my cats is on the way out and I still passed - it's not just one thing, it's everything combined

Good Luck

 

[gamefreakgc]

Mine passed with flying colors. The Smog Tech said he never saw numbers like mine on a 20 year old vehicle.

Don't waste your time or money on that Guaranteed to Pass crap, it's just ethyl alcohol - you can get more benefit by dumping a bottle of octaneboost in your tank and drive it like you stole it before the test - but the key is to bring it in warm to hot

As far as the other suggestions, they are all good. I'm pretty sure one of my cats is on the way out and I still passed - it's not just one thing, it's everything combined

Good Luck

Except that it works! I know all the tricks in the book, hot converter, high octane gas, yada yada and I use fuel injector cleaners on a somewhat regular basis. That stuff dropped my numbers way down.

 

[calnhob]

Okay based on all the helpful comments, here's what I'm going to do/did:

1. Bought new Denso upstream o2 sensor. Don't know the history of mine so might as well change it.

2. Bought the CRC emissions cleaner.

3. Bought the CRC MAF cleaner.

4. Might do another oil change but I changed it only 1K ago.

5. Going to buy the seafoam SS14 spray. I'm assuming it's the spray and not the engine treatment right?

 

[gamefreakgc]

Okay based on all the helpful comments, here's what I'm going to do/did:

1. Bought new Denso upstream o2 sensor. Don't know the history of mine so might as well change it.

2. Bought the CRC emissions cleaner.

3. Bought the CRC MAF cleaner.

4. Might do another oil change but I changed it only 1K ago.

5. Going to buy the seafoam SS14 spray. I'm assuming it's the spray and not the engine treatment right?

Either the Seafoam Spray or the regular liquid Seafoam works but the spray is much easier to use. It's the same stuff but one is in an aerosol spray. Seafoam is a blast to use, I love bellowing huge clouds of smoke down the road . But change your O2 sensor AFTER you use the Seafoam.

 

[calnhob]

Went to the smog station for my retest and it PASSED! What a relief.

All numbers were good except the HC went up to 34 from 15.

Just to summarize in case you are having the same issue passing:

1. Bought a Denso upstream o2 sensor. $46
2. Bought the CRC emissions cleaner. $10
3. Bought the CRC MAF cleaner. $10
4. Oil change Mobile 1 15K extended life and TOYOTA filter. $40
5. Seafoam SS14 spray. Sprayed both in the throttle and in the upstream sensor opening (right before the cat). $10
6. Filled up 1/2 tank of 91 and added a bottle of Isopropyl alcohol.
7. Drove 20 mins on the fwy before the test and got there as it opened.

 

[nissanh]

I had P0430 code in my 100 series cruiser and it is the catalytic converter. Cure is to add a gallon of lacquer thinner to 10 gallons of gas and drive 100+ miles at high rpm (2000-3000).
No more codes and that is what Scotty Kilmer recommended. Take a look at his video about clearing CAT and read reviews. Everyone got positive results including me.

Just make sure to dilute the lacquer thinner with 3-4 gallonsof gas BEFORE pouring it into the tank (just to prevent 100% thinner damaging rubber hose between the tank and the fill cap)

The active metals, Pd, Ir, Rh and Pt are good catalysts and used in so many reactions in the world of chemistry (I've used those in my graduate studies) . Those metals don't degrade but with burned oil and carbon it could by coating a thin layer above the metal preventing its function as a catalyst. Lacquer thinner will remove that coating exposing the metal again!

In addition, you get fuel injectors, combustion chamber, intake valves, etc cleaned!

 

[kball]

I had numbers just like the OP. My trucks numbers were always high since I bought it and came very close to failing just like the OP. I used 2 bottles of Cataclean and did nothing else and it passed with no problems.

Maybe it was a fluke, maybe the other smog place I took it to didn't get the same readings?? (they should all be very close to the same), maybe that crapaclean actually works...? who knows.

I will be using it before the next test as well.