P0300 troubleshooting?

So after 10 years my Tacoma is finally having some issues. I can't believe it still runs after what I put it through. Anyhow, it is throwing a P0300 random misfire code. It doesn't seem to run all that bad, idles fine, will still do 100, but that code is there for a reason. I just pulled the intake and cleaned the MAF, cleaned the throttle body the best I could without removing it, and cleaned the filter. It has fresh plugs, fresh wideband sensors, fresh fuel filter (and pump), ethanol free fuel, and a new battery. Any ideas?

 

What about plug wires?

 

It doesn't have plug wires, and usually when a coil goes tits up the ECU will throw a code for coil#4 bad or whatever. Random misfire usually means any or all cylinders. Also when I pulled the plugs they were all cardboard brown, if one isn't firing they usually look wet/dirty. I was thinking it was fuel because I recently ran some questionable two stroke race fuel (unleaded).

 

I'd compression test it and check valve clearances. And check for vacuum leaks

http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0050029.pdf

 

missed the "random" part. oops.

 

Did a compression check, no issues all were within 10 pounds of each other or so. I guess it could be a fubar cam/valves, but you'd think it would run like crap if that was the case. It's weird, it seems to run just fine and I can hear no perceivable miss. Checking for vacuum leaks now, resealing MAF, PCV, and aftermarket intake boot with a light dab of silicone to be sure. I sprayed the intake down with carb cleaner listening for an increase in RPM. No dice. Also when you unplug any vacuum line the motor stumbles just like a stock motor does. Sometimes the ECU will compensate for a small leak and "hide" it from you, introducing a minor leak will confirm that.

 

Are you still running the stock ECM? A large vac leak should also log a lean code for at least one bank.

Am wondering about your injectors since you mentioned the questionable fuel. Maybe run some techron or other injector cleaner through it if you haven't already.

 

My thoughts too on the injectors. Get them checked out at least at shop that specialized in injector cleaning, balanced and blue printed.

 

Stock ECM, with an URD MAF calibrator to tune for the volant intake. I went into the "enhanced" toyota codes hidden in the ECM and there was an interesting list of codes. Bank 1 too lean. Bank 1 too rich. Bank 1 camshaft too advanced. Bank 1 camshaft too retarded. Exact same codes for bank 2. Interestingly, my scanner wouldn't clear them which leads me to believe they are either hard faults or you need the dealer to clear them. I just replaced the battery today and the terminals were disconnected for several hours. The P0300 code has been there for months, although I just figured out the "enhanced" toyota code thing.

 

Very well could be. This thing has ate a lot of Pemex and shit gas over the years.

 

Sounds like good enough reason the buy a mini-VCI adapter and get techstream up and running on an old laptop so you can read freeze-frame data, clear those codes, and monitor live data to help determine the issue.

 

Talk dirty to me. I didn't know that was possible. I was dreading going to the dealer,you should see the look on their face when I roll into the bay.

Edit: Read up on it a little, turns out the chinese hacked the software and of course there is a trojan in the techstream software that steals your personal data off your laptop. Need an airgapped 'puter or like you said an old one that's been wiped. Do not install on anything you use to access banking, email, etc.