2001 Tacoma Cylinder #3 and #4 misfire

I was driving to work one day when my truck misfired. Saw the check engine turn on so I pulled off the side of the road to check it. Didn’t see anything visibly but I noticed when I accelerate at certain speeds the motor vibrates, and my truck doesn’t idle smoothly anymore. If I gas it hard, my truck runs as smoothly as it did before.

My first thoughts after putting a scanner and seeing codes P0300, P0303, and P0304. Was damn I need new spark plugs. So I went to Autozone bought new spark plugs, even new coil packs and spark plugs wires. After swapping everything out I still had the codes.

After 2 days of googling everything that could go wrong, here’s what I plan to do:

• Put some Lucas Upper Cylinder, and injector cleaner in my gas tank.
• Take off throttle body and clean it with seafoam
• New Throttle Position Scanner
• Test compression of cylinders
• Air/Fuel filter change
• New Cam/Crank shaft sensor
• Fuel injector replacement
• Smoke test
• Fuel pump replacement

Let me know what y’all think of my list, any suggestions, tips, or advice is highly appreciated.

 

Test compression first

 

And have you adjusted the valve shims ever?

 

The list isn’t in order of what I plan to do, but the compression and smoke test are the first 2 on my list. I’ve never adjusted the valve stems, wondering if I could do that or if I should have a mechanic take a look.

 

not the stems, the shims. If they’re out of spec then they could contribute to misfire. Checking em is easy. Should at least check em. Timmy the toolman has a detailed vid on the process.