2-Stoke Fuel in my Tacoma. Now I've got a p0420 code

Earlier this week I put the remainder of my 2-stroke fuel ( less than 1/2 gallon) in my tacoma. It had sta-bil in it and was only 6 months old. I saw on another thread here that usually this wont cause any problem but maybe it could cause so problems with the cat converter. 2 or 3 days or so later and the check engine light pops up. Could this have cause this? The truck is also almost at 208,000 miles so it could just be time for a repair anyways.

If you put it in with a full tank of fuel it should not have caused any problem. If it had Stabil in it I would have just saved it for whatever I had mixed it for.

Thanks. The tank wasnt full but it was probably 3/4 full. I was refilling my 2.5 gallon jug and felt it would be easiest to do the mix by just starting over. I’m probably alot more paranoid with my 2 stroke stuff because I’ve seen so many people mess up their equipment becasue of fuel related issues.

It was probably due anyway, but I’m sure the 2-stroke mix didn’t help any. Burning oil, even if it’s mixed in as part of a 2-stroke mix, contributes to the carbon deposition on the cat’s core… and that’s never good.

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2 stroke fuel in the tank of a modern engine certainly won’t help. It’s hard to say whether it caused this specific problem, but I wouldn’t do that. Diagnosis and repair costs too much these days to take on any additional risk. I take no longer needed fuels to the local auto repair shop and ask them to recycle it or if they won’t, or what the best disposal options are.

Right thanks you guys for the help. It’s the first and last time I’ll put 2
stroke fuel in my car. I used to work in a small engine shop with a kid who
was pretty knowledgable in a lot of areasons but sometimes a bit too
redneck about other things. He’s the one who told me it would be fine,
guess I shouldve double checked.

Please post the cause for your CEL being on. I would be surprised if the blended fuel was the cause but if it was I will need to inform some friends that my past advice might not be quite as certain as I likely made it sound. I recently poured about 1 gallon in my old Blazer but haven’t driven it more than a few miles since. Hopefully I’m safe again this year.

I definitely will. My dad is a mechanic so we’re going to look into it this week.

Many of the posters here said it is ok to do, and Ray has even mentioned it is ok on the show. But like I say, with diagnostic and repair costs what they are on modern engines, it doesn’t make sense to me take on that type of additional risk.

I’m not among them. I think it’s foolhearty for the reason I stated in my earlier post. You burn oil, even mixed with gasoline, and you add carbon to the exhaust stream unnecessarily. That cannot help but reduce the lifespan of the cat converter.

Maybe this is time for some “miracle” cat cleaner liquid in the gas tank plus a good hard run at higher than usual RPMs. What’s to lose?

It’s a thought, but I’d be reluctant to use any additive unless I knew how it would react in the combustion chamber… and/or whether it’d leave any residue in the injection system, or on the valves, as well as how it reacts in the converter.

I’m not an advocate of additives without full knowledge of exactly how they work. To me they’re analogous to medications. All meds work by changing something. I’ve suffered some serious side effects from meds that did what they promised. All additives also work changing something. But, unlike meds, there’s no innate warning system to let me know there’s a side effect.

If the 2-stroke gas was 32:1, 1/2 gal contains 2 oz or 0.0625 qt oil. If your truck gets 25 mpg, it’ll go 250 miles on that, so it’s equivalent to an engine burning a quart of oil every 4000 miles. This will not possibly hurt your truck.

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Even less, it’s 50:1

I learned something here. I would never have assumed that any oil in gasoline would be OK. I would have assumed there would be a problem. Good luck.

The volume of oil seems hardly noticeable and the current variety of 2 stroke oils that are formulated to function at 50:1 ratios seem to burn very clean. When cleaning spark arresters I see that the pistons are bright and carbon free. But in today’s automobiles with catalytic converters costing hundred$ it would be worthwhile to be careful.

So I reset the CEL per suggestion of my Dad and it has not turned back on
after probably 60 miles now. I’ll still keep everyone posted if it changes.

P0420 on my old truck was taking 100-250 miles to drive after reset before it would come back

have you ever replaced a downstream oxyden sensor[s] in your Tacoma?

200K miles seems to suggest it is on the last leg if it is still an OEM one, that sensor might condemn a working cat and it is usually very cheap to replace

if your dad can check the sensor condition with an oscilloscope - you would know for sure

I’ve never even heard of a oscilloscope. I’ll ask him about it later this
evening though. I just figure change both the sensors first and reset again
to see if it changed. Thanks for that tip, definitely helpful.

from you answer I assume you still have OEM sensors

likely it is V6 and you have 2 downstream sensors - replace both, they are cheap

don’t touch the upstream ones - do not over-complicate things with too many changes