Engine Misfires Only After a Hot Engine Start

2001 Tacoma 2.4L L4 A/T 2WD Regular Cab DLX 186,000 miles
Engine misfires ONLY after a hot engine start (P0304 - Cylinder 4 Misfire Detected). After a hot start and driving for about 1 minute, the engine smooths out. Plugs and ignition coils have been replaced. All four plugs looked clean. No signs of burn, carbon or oil on plugs. I have replaced the fuel filter, removed and cleaned the throttle control and idle air control valve and replaced both gaskets. Cleaned mass airflow sensor. Removed and cleaned all four fuel injectors and replaced upper and lower fuel injector O-rings. All vacuum hoses look good, and no vacuum leaks have been found. The only other issue that I am experiencing is an exhaust leak, which is coming from a hole in the muffler. Water coolant temperature is in the normal range. Next step is to check fuel pressure but at the moment I don't have the equipment to do so (gave it all away after I retired). Over the course of the last 7 years the truck has been driven very little, however being the original owner I frequently added Techron fuel additive to the gas to maintain a clean fuel system. This was evident when I pulled and cleaned the injectors. Any help that you can provide will be much appreciated.

 

It seems you covered all the common possibilities.. others may include defective aftermarket coil pack, even if it came in a Toyota box doesn't mean it's actually a Toyota made part as there is a large market of counterfeit Toyota parts sold at non dealer parts stores.. cam / crank shaft sensor could cause a p0304 code as well, possible intake leak also..there's a few dozen possibles and unfortunately if the easy stuff hasn't fixed it then maybe a good shop is in order and at worst a Stealership may be needed..to find the cause..Best of luck..Hopefully someone chimes in soon to help you with their personal experience with a similar issue..