Is it safe to run a gallon of Lacquer Thinner in the gas tank to try and clear a code P0420? (QX4 2003 91,000 miles)

[dk203040]

Is it safe to run a gallon of Lacquer Thinner (to 10 gallons of gas) in the gas tank, to try and clear code P0420?
(QX4 2003 91,000 miles).

I've read comments of success stories for clearing the P0420 code.
Also read comments suggesting that Lacquer thinner could possibly damage seals and rubber.

Any other additives worth a try?

QX4 runs well, but long time very poor gas mileage.

The P0420 code came up shortly after the #3 ignition coil was replaced.
(Only drove about 40 miles with the bad coil before replacing.)

[mdmellott]

Is it safe to run a gallon of Lacquer Thinner
Any other additives worth a try?

I wouldn't risk it. Lacquer thinner can degrade plastics in fuel system components.
Cataclean is the product I finally tried, which successfully resolved my inefficient catalytic converter. Just follow the instructions. Add a 16oz bottle to your tank when it is down to about one-eighth full. Drive it for at least 15 miles and then fill up the tank no more than half full. Fill up as usual when it gets down to about an eighth full. I had to repeat the process in about 6mo when the code came back. It has been well over a year since then and no more P0420 or P0430 codes have popped up.

[mdmellott]

The P0420 code came up shortly after the #3 ignition coil was replaced.
(Only drove about 40 miles with the bad coil before replacing.)

It is also possible the inefficient cat code P0420 may be due to less efficient #1 and #5 coils relative to the new #3 coil. That right bank (bank 1) works in concert with fuel delivery controlled by the upstream O2 sensor dictating the same amount fuel injection into all 3 cylinders on that right bank. If the voltage delivery from coils #1 and #5 is less than the new #3 coil, the ignition event and fuel burn at #1 and #5 could be weak while #3 is normal. Your downstream O2 sensor could see this as an inefficient catalytic converter when it is actually an out of balance set of coils. Coils get weak over time. When one goes bad because of age it's a sure bet the others are soon to follow.

O2 sensors also get less efficient over time. Replacing them is part of routine maintenance. It is the downstream O2 sensor that is flagging that P0420 code. The question is whether or not it is sensing the truth about your exhaust gases. Since your code popped up just after replacing #3 coil, it may be more of an efficiency balance issue but the catalytic converter may still be a bit too dirty.

All of these parts of the system play together in concert so they all need to be playing their part well.

[dk203040]

The P0420 code came up shortly after the #3 ignition coil was replaced.
(Only drove about 40 miles with the bad coil before replacing.)

It is also possible the inefficient cat code P0420 may be due to less efficient #1 and #5 coils relative to the new #3 coil. That right bank (bank 1) works in concert with fuel delivery controlled by the upstream O2 sensor dictating the same amount fuel injection into all 3 cylinders on that right bank. If the voltage delivery from coils #1 and #5 is less than the new #3 coil, the ignition event and fuel burn at #1 and #5 could be weak while #3 is normal. Your downstream O2 sensor could see this as an inefficient catalytic converter when it is actually an out of balance set of coils. Coils get weak over time. When one goes bad because of age it's a sure bet the others are soon to follow.

O2 sensors also get less efficient over time. Replacing them is part of routine maintenance. It is the downstream O2 sensor that is flagging that P0420 code. The question is whether or not it is sensing the truth about your exhaust gases. Since your code popped up just after replacing #3 coil, it may be more of an efficiency balance issue but the catalytic converter may still be a bit too dirty.

All of these parts of the system play together in concert so they all need to be playing their part well.

Thank you for 2 great detailed replies. I'm happy to read a good success story with a commercial product designed for use in the gas tank. That feels much safer to try vs. using lacquer thinner.

Here's more part to my story which supports your discussion about the coils...
A few weeks before #3 coil needed to be replaced, coil #5 went out suddenly with a limp, and was replaced the next day. Other than that, the QX4 always runs well, (except when one of the coils goes bad.)

The gas mileage has been seriously terrible for a long time, with no solution recommended by the mechanic shop that works on the truck.

Whatever is causing the extremely poor gas mileage probably is related to why both, the coils are going out, and maybe causing the cat code P0420.

In the fairly recent past I did get a code for the rear bank #2 02 Sensor. (I forgot how we fixed that code).
The truck also uses oil like all the rest of these trucks, but no smoking, and no smells from the exhaust. I guess most owners just live with the oil usage.

Thank again for the help!!! Very much appreciated.

[mdmellott]

Consuming a lot of oil, as you described, will certainly foul up the cats. I would do the Cataclean treatment twice, back to back, to be sure and get the cats more reasonably clean. After that, at your next oil and filter change which should be every 3000 to 3500 miles, a Seafoam High Mileage Motor Treatment additive would help a bit on your MPG and oil consumption. Pour 4oz into your motor and the rest into fuel tank. It's all good medicine.

[dk203040]

Consuming a lot of oil, as you described, will certainly foul up the cats. I would do the Cataclean treatment twice, back to back, to be sure and get the cats more reasonably clean. After that, at your next oil and filter change which should be every 3000 to 3500 miles, a Seafoam High Mileage Motor Treatment additive would help a bit on your MPG and oil consumption. Pour 4oz into your motor and the rest into fuel tank. It's all good medicine.

1) So, add 16 oz Cataclean when tank is down to 1/8 full, ...drive 15 miles, ...then fill gas tank to 1/2 full;
then run down to 1/8 tank and repeat add 16 oz Cataclean again. Right?

2) How often is best to use, (or worth using), the Seafoam High Mileage Motor Treatment additive?
I did see good reviews for this product.

Thank you again!!!

[mdmellott]

1) So, add 16 oz Cataclean when tank is down to 1/8 full, ...drive 15 miles, ...then fill gas tank to 1/2 full;
then run down to 1/8 tank and repeat add 16 oz Cataclean again. Right?

2) How often is best to use, (or worth using), the Seafoam High Mileage Motor Treatment additive?
I did see good reviews for this product.

1) That's right
2) I have used it twice in my PF over the past 5yrs to clean up the oil passages in my engine and to free up an intermittently sticky VVT solenoid valve and the rest in the tank help clean up combustion chambers and the fuel system. Top tier detergent gasolines and the detergents in high quality motor oils do their job well enough but once in awhile these older engines just need an extra cleaning to keep them running smooth.

I have 236K miles on my PF. It consumes less than 3/4 of quart between oil changes and the MPG is as good as it was when it was brand new.

[Mike W.]

Did I miss it? Have you tried changing the post cat O2 sensor for that side? My '03 Q did code for that once, shortly after I go it nearly 50K or so, currently at ~180K, but then went away. Actually think it was P0430, the other side. Regardless. It has since coded for that again, which I replaced it for, and the other side, heater circuit which I replaced it for, and currently at ~180 with no codes. And unfortunately very high oil consumption. (I've got to do something soon before I trash the cats)

Anyway, if you haven't, try the O2 sensor and cross your fingers. You're mileage is low, but it's not that much time or cost to put in a new O2 sensor. Might not do a thing, a bottle of Cat a clean is far cheaper and easier, but don't discount the sensor itself.

[dk203040]

Did I miss it? Have you tried changing the post cat O2 sensor for that side? My '03 Q did code for that once, shortly after I go it nearly 50K or so, currently at ~180K, but then went away. Actually think it was P0430, the other side. Regardless. It has since coded for that again, which I replaced it for, and the other side, heater circuit which I replaced it for, and currently at ~180 with no codes. And unfortunately very high oil consumption. (I've got to do something soon before I trash the cats)

Anyway, if you haven't, try the O2 sensor and cross your fingers. You're mileage is low, but it's not that much time or cost to put in a new O2 sensor. Might not do a thing, a bottle of Cat a clean is far cheaper and easier, but don't discount the sensor itself.

In addition to the P0430 code that you got on your Q, did you also get a specific code for your O2 sensor, or did you just go ahead and change out the sensor without an "O2 Sensor" code, and that worked to clear the P0430 that you got on your truck?

Was it difficult to remove your post cat O2 sensor?

So far I put in 16 oz of Cataclean and I still have the P0420 pending, (after I manually deleted the code).
I'm planning on trying another 16 oz of Cataclean, when I get back down to 4 gallons.

[mdmellott]

It has been over a year since I used Cataclean to get rid of what was a persistent P0430 code popping up every couple of months or so prior. It popped back up this morning after a short drive. My PF typically only sees short drives over the past few years so my cats never really get very hot or hot for very long to burn off much of what gunk is polluting my left cat. My coils, injectors, and O2 sensors are all fairly newish and the scans of my engine indicate the sensors are behaving normal, with the exception of an inconsistent blip in the otherwise steady state voltage reading from oxygen sensor B2S2. Someday, maybe, I might replace my cats but for now and once again a Cataclean treatment is what the doctor ordered. "Physician, heal yourself!" is the proverb that comes to mind.

[mdmellott]

No more blip showing up in the scan graph of my downstream O2 sensor and no more P0430 DTC. Everything is back to normal, for now at least.

[dk203040]

Did I miss it? Have you tried changing the post cat O2 sensor for that side? My '03 Q did code for that once, shortly after I go it nearly 50K or so, currently at ~180K, but then went away. Actually think it was P0430, the other side. Regardless. It has since coded for that again, which I replaced it for, and the other side, heater circuit which I replaced it for, and currently at ~180 with no codes. And unfortunately very high oil consumption. (I've got to do something soon before I trash the cats)

Anyway, if you haven't, try the O2 sensor and cross your fingers. You're mileage is low, but it's not that much time or cost to put in a new O2 sensor. Might not do a thing, a bottle of Cat a clean is far cheaper and easier, but don't discount the sensor itself.

Mike W, I just found you message. Somehow I missed. Thank for the reply. So I've had no codes for the same side downstream O2 sensor? And... No I did not replace it.
I understand you saying the you replaced your downstream 02 sensor, (with no mention of a code), and that solved the P0420 or P0430 code. ...Is that correct???
...if so, definitely "worth a try."

I did separately run two bottles of Cataclean in the gas tank, and no joy.

Before the P0420 code, I did get a code for the downstream O2 sensor on the other side, (the driver's side), and that code disappeared by itself for some months, then briefly came and went again.

The truck consistently runs fine except for very low gas mileage. Mostly only very short drives to work and back with auto climate control running always.

So bottom line, sounds like you're saying changing the same side downstream 02 worked for, even though no code for that 02 sensor.

Thanks for taking the time to reply to my problem post.

[dk203040]

Is it safe to run a gallon of Lacquer Thinner
Any other additives worth a try?

I wouldn't risk it. Lacquer thinner can degrade plastics in fuel system components.
Cataclean is the product I finally tried, which successfully resolved my inefficient catalytic converter. Just follow the instructions. Add a 16oz bottle to your tank when it is down to about one-eighth full. Drive it for at least 15 miles and then fill up the tank no more than half full. Fill up as usual when it gets down to about an eighth full. I had to repeat the process in about 6mo when the code came back. It has been well over a year since then and no more P0420 or P0430 codes have popped up.

You're a lucky man! I followed your instructions with two rounds of Cataclean and no joy so far. ...Any other ideas??? Thanks for your info.

[VStar650CL]

You're a lucky man! I followed your instructions with two rounds of Cataclean and no joy so far. ...Any other ideas??? Thanks for your info.

Then chances are your cat is actually dead and no amount of cleaner is going to resurrect it. Cataclean is just what the name implies, a cleaner. It's very effective for removing soot and carbon, and even small amounts of phosphorous and zinc scale. It won't help a cat that's badly poisoned or whose catalytic surfaces are clumped or decomposed.

[mdmellott]

Any other ideas???

Test and verify:
1. A leaky fuel injector could throw off fuel efficiency and trigger an inefficient cat code. A fuel pressure test to check for a leaky fuel injector would verify this.
2. If the cat is dead, the temperature of the cat pipe right at its intake neck will be about the same temperature as the cat pipe right at its output neck. The output end should be about 20% hotter is the cat is good. A cheap thermal scan gun would verify this. https://www.amazon.com/gp/aw/d/B07VTPJXH9/?th=1
3. If your coils are now a mix of old and new original and aftermarket, that could through off fuel combustion efficiency balance and trigger an inefficient cat code. A brand new set of 6 original Nissan/Infiniti coils (22448-8J115) are super inexpensive on e-bay. https://www.ebay.com/itm/358599108411
4. An inefficient downstream O2 sensor could trigger a false positive indication of an inefficient cat. An inexpensive generic scan tool with a graph view of the sensor should show a steady state voltage reading, somewhere around .3V at idle. If the voltage is fluctuating randomly or flatlined, the O2 sensor is bad. https://www.amazon.com/dp/B00UJV3E12

[VStar650CL]

2. If the cat is dead, the temperature of the cat pipe right at its intake neck will be about the same temperature as the cat pipe right at its output neck. The output end should be about 20% hotter is the cat is good. A cheap thermal scan gun would verify this

Md is absolutely right about this, and it's the first thing you should do. There's no point in screwing around looking at other hardware if the cat is a dead duck.

1. A leaky fuel injector could throw off fuel efficiency and trigger an inefficient cat code. A fuel pressure test to check for a leaky fuel injector would verify this.

Could be, but chances are very great that it would be throwing a P0172.

3. If your coils are now a mix of old and new original and aftermarket, that could through off fuel combustion efficiency balance and trigger an inefficient cat code. A brand new set of 6 original Nissan/Infiniti coils (22448-8J115) are super inexpensive on e-bay. https://www.ebay.com/itm/358599108411

+1. Crappy coils can be a hidden culprit in a lot of things. Not likely, but definitely possible.

4. An inefficient downstream O2 sensor could trigger a false positive indication of an inefficient cat. A generic scan tool with a graph view of the sensor should show a steady state voltage reading, somewhere around .3V at idle. If the voltage is fluctuating randomly or flatlined, the O2 sensor is bad.

You can't really do a meaningful check on a rear O2 at idle except to make sure it isn't flatlined. The ECM doesn't even look at the readings at idle, you need to be warm with the RPM's elevated. Then you'll see oscillations of about 2 seconds from around 0.3~0.8V. The ECM judges the health of the sensor by voltage, the health of the cat by oscillation frequency compared to the front O2. The upshot is, the ECM's are pretty good at discriminating bad cats from bad sensors, so if your only code is a P0420/P0430 then it's unlikely the sensor is the culprit.

That all said, the one thing which can and does routinely cause false P0420/P0430's is exhaust leaks, especially right around one of the O2's. Sometimes pinholes aren't audible enough for your ear to notice, but the sensors will notice the extra oxygen. Leaks near the front O2 will make the ECM think the mixture is wrong and can indirectly cause a false cat code, while leaks near the rear O2 directly affect the oscillation rate. Have an assistant plug your pipes with shop rags and then listen in the area of the cat, the extra backpressure will make even the tiniest leak very audible.