99 Toyota Tacoma miss fire on one cylinder

It's a v-6 ... well maintained was running great.. not using any oil . It just suddenly started missfireing on one cylinder as the code indicated #3. It's never had any major work done on the engine since I've had it over 10 years. So I changed all the spark plugs... changed the coils and the plug wires. I also changed all the injectors. Still miss firing on #3. I checked the OHMS on the injectors and all was good. I replace the spark plug with another spark plug... no change yer. So I switched out the coil with a different coil and issue still is there. Where do I look now? One other thing I just noticed as I took it out to see if running it hard would clear it up. I floored it a 50mph and it fell on it's face...actually started slowing down. Wasn't backfiring tho...just fell flat and kept slowing til I took pedal off the floor then it calmed back to where it was. Repeat and same results. What can it be?

 

You should check the compression on that cylinder, probably all of them while you're at it.

You might find it's lower than the rest. If it's low, it could be for a number of reasons but at least you'll know where to focus.

 

There is also a test you can have done that will test the coolant for combustion gas to check for a head gasket leak.

 

I would suspect something is not right with the wires to the #3 injector. Perhaps it's opened up and the injector is not getting any juice???

 

Wouldn’t be a bad idea to get a noid light and test the injectors that way either. The few times I’ve dealt with this same issue it’s been a head gasket, but it’s best to rule out the easy stuff first.

 

when was the last time valve clearances were checked?