Failed smog test twice. Need advice.

[StreetCreeper]

Failed the California smog test and re-test due to high NO reading.


On the retest I missed the mark by about 65ppm for NO. So I'm sorta close.



Vehicle background:

1997 3.4L. This is a California truck with about 390,000 miles on original engine and transmission.

Changed plugs and wires about 2000 miles ago.

After 1st failed test, I cleaned the MAF and replaced the upstream O2 sensor.

Second test got me to within 65ppm of the passing level.

Since I'm only 65ppm from passing — I'm wondering if there is anything I can tinker with or try to do that might help lower that level down just enough to allow it to pass?

Obviously I can replace the cat which is the original, but I'd be more than happy to try "alternative" methods as well! I'm not above burning sage, hitting the bong and dancing around the truck if it will somehow please the smog gods and help it pass....(it doesn't btw...found that out last week).

So anyone have any real-world facts, tricks, tips, suggestions, rumors or old wives-tales about lowering NO levels?

 

[SilverRidgeRunner1]

Failed the California smog test and re-test due to high NO reading.


On the retest I missed the mark by about 65ppm for NO. So I'm sorta close.



Vehicle background:

1997 3.4L. This is a California truck with about 390,000 miles on original engine and transmission.

Changed plugs and wires about 2000 miles ago.

After 1st failed test, I cleaned the MAF and replaced the upstream O2 sensor.

Second test got me to within 65ppm of the passing level.

Since I'm only 65ppm from passing — I'm wondering if there is anything I can tinker with or try to do that might help lower that level down just enough to allow it to pass?

Obviously I can replace the cat which is the original, but I'd be more than happy to try "alternative" methods as well! I'm not above burning sage, hitting the bong and dancing around the truck if it will somehow please the smog gods and help it pass....(it doesn't btw...found that out last week).

So anyone have any real-world facts, tricks, tips, suggestions, rumors or old wives-tales about lowering NO levels?

I hear if u ran Premium fuel for couple weeks and retest it would pass or not. I read that somewhere but cannot recall.

 

[Konkordmusk]

Let's start by defining why high NO levels happen; almost exclusively due to high engine temperatures. Normally I'd say cooling system issues, but also knowing that you have such high mileage, I would instead say that it's possible you have enough carbon build-up in the combustion chamber to increase compression enough to cause the high temperature condition. I've seen it before. Try some Seafoam treatment.
Also ensure your cooling system is in order. Lastly, inspect for vacuum leaks, spray some brake cleaner around some vacuum lines and if your idle rises, you have a leak. A vacuum leak could cause a lean fuel condition, causing excessive combustion temperature.

 

[s20004runner]

Other than the usuals (engine cleaning, premium fuels, upstream O2 sensor replacement, etc), I learned that Cat's optimal operating temp is pretty high and they can cool quickly during my last CA emission.

If you had let your engine/Cat cool down before the test, you can try not letting it cool or heat up the Cat.

 

[StreetCreeper]

I hear if u ran Premium fuel for couple weeks and retest it would pass or not. I read that somewhere but cannot recall.

I've come across that as well. I guess higher octane burns at a lower temp. I think it may be worthwhile to run it during the test. Who knows if it will help or not though.

Let's start by defining why high NO levels happen; almost exclusively due to high engine temperatures. Normally I'd say cooling system issues, but also knowing that you have such high mileage, I would instead say that it's possible you have enough carbon build-up in the combustion chamber to increase compression enough to cause the high temperature condition. I've seen it before. Try some Seafoam treatment.
Also ensure your cooling system is in order. Lastly, inspect for vacuum leaks, spray some brake cleaner around some vacuum lines and if your idle rises, you have a leak. A vacuum leak could cause a lean fuel condition, causing excessive combustion temperature.

I think you are on the money in terms of the carbon buildup. This truck runs great now, but it was neglected most of its life and I can guarantee there is a lot of build up inside.

I'm almost afraid of Seafoam though. I worry that I may have so much buildup that it may cause other problems if it all starts to come out at once from some cleaner.

Would I need to change plugs again after a Seafoam treatment?

I've checked for vac leaks and found none, but that was a few thousand miles ago. Perhaps I inadvertently caused a leak while working on things. I'll check again.

The cooling system is good as far as I can tell. I don't have an after market monitor but I haven't noticed the dash gauge changing or any other signs of higher than normal temps.

Other than the usuals (engine cleaning, premium fuels, upstream O2 sensor replacement, etc), I learned that Cat's optimal operating temp is pretty high and they can cool quickly during my last CA emission.

If you had let your engine/Cat cool down before the test, you can try not letting it cool or heat up the Cat.

Interesting that you mention this. The place I go to for the smog test advertises most vehicles in & out in 15 minutes. However, both times I went there, my truck sat for about 45 minutes before they took it in for testing.

I don't know if waiting is good or bad. On the one hand the engine is cooling down and that should help lower the Nox levels right? Yet as you mentioned, the cat may not be at the optimal temp to convert that Nox which means the reading will be high.

 

[s20004runner]

I've come across that as well. I guess higher octane burns at a lower temp. I think it may be worthwhile to run it during the test. Who knows if it will help or not though.



I think you are on the money in terms of the carbon buildup. This truck runs great now, but it was neglected most of its life and I can guarantee there is a lot of build up inside.

I'm almost afraid of Seafoam though. I worry that I may have so much buildup that it may cause other problems if it all starts to come out at once from some cleaner.

Would I need to change plugs again after a Seafoam treatment?

I've checked for vac leaks and found none, but that was a few thousand miles ago. Perhaps I inadvertently caused a leak while working on things. I'll check again.

The cooling system is good as far as I can tell. I don't have an after market monitor but I haven't noticed the dash gauge changing or any other signs of higher than normal temps.




Interesting that you mention this. The place I go to for the smog test advertises most vehicles in & out in 15 minutes. However, both times I went there, my truck sat for about 45 minutes before they took it in for testing.

I don't know if waiting is good or bad. On the one hand the engine is cooling down and that should help lower the Nox levels right? Yet as you mentioned, the cat may not be at the optimal temp to convert that Nox which means the reading will be high.

I didn't do the seafoam, but got one of those BG engine cleaning thing at a shop. (similar concept as seafoam I think).

I don't know enough, but from my basic knowledge, I think the cat at its optimal temp will convert more nox than cooler engine emitting less nox. So I think 45mins of cooling time may matter.

 

[jeremyc74]

I don't know if waiting is good or bad. On the one hand the engine is cooling down and that should help lower the Nox levels right? Yet as you mentioned, the cat may not be at the optimal temp to convert that Nox which means the reading will be high.

I think you're onto something there.

I don't know a lot about how they conduct the test, but the NO levels drop substantially during the 25MPH portion of the test, even though the RPM is still very close to the same. The max allowable value is higher for that portion, so that tells me they're expecting it to go up on some vehicles. I'll bet if you can get it in there hot it will pass.

Something else you might try is overinflating the tires. Since you're right on the limit that might lower the rolling resistance and bring the RPM down a little to get that last little bit. :first:

(Forgive me if that's illegal, I'm not up on CA emissions regulations)

Alternatively, you might swap on a set of lighter, taller tires to accomplish the same thing.

 

[white_n_slow]

New cats was the only solution for me. Squeaky clean after that. At 390 miles, if they are original, they are most certainly not doing their job any more. I replaced mine at 300k.

I have tried all the alternative methods: heet, e85, driving to the emissions shop in 1st or 2nd gear, various tuning tricks, (won't admit to above mentioned bong dance). You need cats. That's my $.02 Even if you squeeze by this test, you will certainly fail the next, and be making the baby polar bears cry in the meantime.

 

[StreetCreeper]

I didn't do the seafoam, but got one of those BG engine cleaning thing at a shop. (similar concept as seafoam I think).

I don't know enough, but from my basic knowledge, I think the cat at its optimal temp will convert more nox than cooler engine emitting less nox. So I think 45mins of cooling time may matter.

It's a fine line I guess. I'll have to do some more digging and figure out if there is an optimal time to smog in relation to the engine temp and cat temp.

I think you're onto something there.

I don't know a lot about how they conduct the test, but the NO levels drop substantially during the 25MPH portion of the test, even though the RPM is still very close to the same. The max allowable value is higher for that portion, so that tells me they're expecting it to go up on some vehicles. I'll bet if you can get it in there hot it will pass.

Something else you might try is overinflating the tires. Since you're right on the limit that might lower the rolling resistance and bring the RPM down a little to get that last little bit. :first:

(Forgive me if that's illegal, I'm not up on CA emissions regulations)

Alternatively, you might swap on a set of lighter, taller tires to accomplish the same thing.

I'll definitely over inflate the tires! Might not help but it sure can't hurt it either. I think if I do enough "little things" like this — I might just tip the scales in my favor on the next test.

New cats was the only solution for me. Squeaky clean after that. At 390 miles, if they are original, they are most certainly not doing their job any more. I replaced mine at 300k.

I have tried all the alternative methods: heet, e85, driving to the emissions shop in 1st or 2nd gear, various tuning tricks, (won't admit to above mentioned bong dance). You need cats. That's my $.02 Even if you squeeze by this test, you will certainly fail the next, and be making the baby polar bears cry in the meantime.

I'm doing all this with the understanding that eventually I will have to replace the cat. Though I would prefer not to do it right now if I can put it off until after I win the Powerball lotto next week.

Now you have me wondering if I have TWO cats!

While the bong dance didn't work for me last week, I think I'm going to give it another shot this evening...and tomorrow evening too...in the name of science I mean.

​

 

[white_n_slow]

Sorry, the two cats was in reference to my Lexus. I didn't mean to confuzzle

 

[kball]

Streetcreeper, you are the perfect test subject for this product!! They will double your money back for the product but not for the test but it's still worth a shot!

http://www.amazon.com/CRC-05063-Guaranteed-Emissions-Formula/dp/B000CIPUR8

 

[StreetCreeper]

Streetcreeper, you are the perfect test subject for this product!! They will double your money back for the product but not for the test but it's still worth a shot!

http://www.amazon.com/CRC-05063-Guaranteed-Emissions-Formula/dp/B000CIPUR8

Think I may give this or seafoam a go along with some other odds & ends. It won't be very scientific though as even if I pass, I won't know which or how much of whatever I did actually helped.

If I wasn't broke and this wasn't my DD, I'd run just the CRC cleaner without any other changes and then compare results.

Of all the testimonials for this product, I didn't see a single honest before & after comparison. Lots and of people say it worked, but nobody offers any evidence beyond their word.

Still though, for $9 at Walmart — I thinks it's worth running it with a tank of fuel I guess.

 

[Jhelms]

Run the rig down to, or just below 1/4 tank. Pour a bottle of everclear or denatured alcohol (ethanol) into the tank before going to emissions (1/4 gallon is enough). This should get her through. When done, take her to the gas station and fill up the tank to dilute the rest. :cheers:

 

[StreetCreeper]

Run the rig down to, or just below 1/4 tank. Pour a bottle of everclear or denatured alcohol (ethanol) into the tank before going to emissions (1/4 gallon is enough). This should get her through. When done, take her to the gas station and fill up the tank to dilute the rest. :cheers:

At first I scoffed at the idea...but then I thought about it and it makes sense. I guess alcohol burns cleaner right? Cleaner burn = less emissions.

When you say denatured alcohol, are you talking about any kind or something specific? Will the stuff at Walmart suffice?

So far I'm thinking that before the next test, I'll run a bottle of CRC emission stuff through a full tank, then change my oil, double check for any vac leaks, then air up the rear tires above normal range, put a quarter tank of premium in and then finally some alcohol.

As previously stated by forum members, my thinking is that the CRC will possibly help reduce carbon buildup and lower the operating temp thereby lowering the NOx before the cat. Then the oil change may help eliminate any dirty vapor crap the PCV valve might suck up (I'm due for a change anyways). As stated earlier, the extra air in the tires will reduce rolling resistance and hopefully reduce emissions. The alcohol I assume will simply burn cleaner and reduce emission levels as well. The preimum fuel should burn cooler which I guess will reduce NOx levels specifically. And lastly, I'll figure out what time the shop opens and then drive the truck for about a 45 minutes on the freeway and then time my arrival to the smog shop for right as they open. Hopefully this will ensure that the cat is tested at its optimal temperature.

If all this doesn't lower my NOx by 65ppm — then I'll just buy a new cat.

I'll post up the new test next week when I test again. It may not be scientific, but if I document all the tests, and report exactly what I did between each test, it may well help others in the same boat as me somewhere down the road.

Thanks to everyone who replied with their thoughts. Pass or fail — I appreciate the help.

 

[cashmoney]

Pass or fail this will be interesting to see.

 

[gamefreakgc]

You have high HC and NOx, just NOx is over the limits and HC is not.

This chart is very helpful, it's from the 3VZ-E but it's still relevant (although not all 5VZ-FE's have EGR's). See attached.

Usually when all readings start to creep up, it's the cat that is failing. High HC only indicates a rich engine, high CO means a lean engine.

A cheap fix that can sometimes work is a new PCV valve. More nasty gases go back into the intake to be burnt off that way!

 

[StreetCreeper]

You have high HC and NOx, just NOx is over the limits and HC is not.

This chart is very helpful, it's from the 3VZ-E but it's still relevant (although not all 5VZ-FE's have EGR's). See attached.

Usually when all readings start to creep up, it's the cat that is failing. High HC only indicates a rich engine, high CO means a lean engine.

A cheap fix that can sometimes work is a new PCV valve. More nasty gases go back into the intake to be burnt off that way!

I replaced the original PCV about 20,000 miles ago. Not sure if it would be failing already but I'll definitely check it before I retest.

I think you are correct. After 20 years and nearly 400,000 miles, the original cat just isn't working quite like it should. Even the smog tech was surprised it was doing as well as it did for being original.

 

[BrianSD_42]

Let us know how it goes!

 

[s20004runner]

I replaced the original PCV about 20,000 miles ago. Not sure if it would be failing already but I'll definitely check it before I retest.

I think you are correct. After 20 years and nearly 400,000 miles, the original cat just isn't working quite like it should. Even the smog tech was surprised it was doing as well as it did for being original.

400,000 miles!!

That's great, that means my t4r w/ 215K miles still has a lot of life left. good luck!

 

[Jhelms]

At first I scoffed at the idea...but then I thought about it and it makes sense. I guess alcohol burns cleaner right? Cleaner burn = less emissions.

When you say denatured alcohol, are you talking about any kind or something specific? Will the stuff at Walmart suffice?

So far I'm thinking that before the next test, I'll run a bottle of CRC emission stuff through a full tank, then change my oil, double check for any vac leaks, then air up the rear tires above normal range, put a quarter tank of premium in and then finally some alcohol.

As previously stated by forum members, my thinking is that the CRC will possibly help reduce carbon buildup and lower the operating temp thereby lowering the NOx before the cat. Then the oil change may help eliminate any dirty vapor crap the PCV valve might suck up (I'm due for a change anyways). As stated earlier, the extra air in the tires will reduce rolling resistance and hopefully reduce emissions. The alcohol I assume will simply burn cleaner and reduce emission levels as well. The preimum fuel should burn cooler which I guess will reduce NOx levels specifically. And lastly, I'll figure out what time the shop opens and then drive the truck for about a 45 minutes on the freeway and then time my arrival to the smog shop for right as they open. Hopefully this will ensure that the cat is tested at its optimal temperature.

If all this doesn't lower my NOx by 65ppm — then I'll just buy a new cat.

I'll post up the new test next week when I test again. It may not be scientific, but if I document all the tests, and report exactly what I did between each test, it may well help others in the same boat as me somewhere down the road.

Thanks to everyone who replied with their thoughts. Pass or fail — I appreciate the help.

It will say "denatured alcohol" right on the can (usually comes in a can - google it). Can be found at most any hardware store and even walmart. Or go to the liquor store and buy a large bottle of everclear 190 proof. Betting you will have little trouble passing doing this as close as you are.

And on the bright side, it can help clean up cylinder walls, chambers build up and injectors