P0300 and poor gas mileage on 3rd Gen MT

Hi guys I have a 2019 TRD OR 6spd Taco with 46k miles that is experiencing its first issue. Maintenance has been UTD per Toyota schedule.

Twice in the last 3 months I've experienced a misfire. Both times were directly after turning the truck on (not cold, after stopping at a gas station with the engine warm). The first time the truck refused to idle and stalled twice, then I let it sit for a second, turned it back on and it ran fine. No CEL. I noticed afterwards that I had a little loss of power in the upper rev range and that I lost about 1.5 mpg in combined driving. I changed air filter, ran injector cleaner through it and seem to do okay other than poor mpg. Then last week, again after stopping at a convenience store with engine warm, immediately upon starting it ran very poorly and would not rev past 2.5k rpm with multiple cylinders misfiring. I turned it off and back on and it ran fine, but with continued poor mileage. This time it threw a CEL.

I ran the codes today and the only one that came up was P0300 which is multiple cylinder misfire.

I know this can be spark plug, MAF etc just curious if anyone has experienced anything similar before I just start replacing stuff. It seems since turning the truck off and back on resolves the acute issue it could be a sensor or something rather than spark plugs?

Thanks

 

You say both times you were stopped at a gas station; did you fuel up on both occasions? That would lead me to think 'evap system'. There are a LOT of things that this could be... if you don't have one, I would invest in a scan tool with 'live data' capability so that you can get a better idea of what's happening. Fuel trims and misfire counters could be especially helpful here.

 

Thanks for reply, both times were after driving about 2 miles (so engine warm but not at full operational temp) and I just stopped to get snacks, did not fill up or remove gas cap. Cool. I have a blue driver which looks like has live data capability if I leave it plugged in. So I guess I just leave it in and wait for it to happen again? I honestly thought it could be an O2 sensor or something since I lost some power in the higher rev range after the VVTI but iirc that would throw a different code. I paid for the "100k" warranty from Toyota when I bought the truck so I could maybe get them to look at it for free it's just one of those issues that is so intermittent they're likely not to find anything and I'd be without a ride for a couple days..

 

If you get a code again, don't clear it. The shop will at least have that as a starting point.

Here is some generic reading re the code you did pull. Not saying to do anything with this info, but worth having some ideas.

Low fuel pressure made me wonder if your truck is one covered under the fuel pump recall?

And there were issues with crank sensors as well.

https://www.700r4transmissionhq.com/p0300-toyota-tacoma/