So my 2000 SR5, 3.4, 230k. 6 months ago I had a shop replace the starter, and while I had it there I had them go ahead and replace the plugs and wires. They also did some coil pack work but from further investigation I think they only replaced some boots as the coils were not the same. 1 Denso and 2 others with no markings. All 3 looked pretty old, but I cant say 100%. The hand written receipt is hard to read and not clear on what he actually did with the coil packs. Im not going back to this shop as there is a bit of a language barrier and communication is tough.

So....... recently it started misfiring and running very rough. P0303 and 0300. I went ahead and ordered off brand coil packs from Amazon and another set of Denso wires thinking it had to be the #3 coil or coils. Replaced packs and the wires and still had the same codes and crappy idle and obvious misfire. My thoughts about the plugs is that they are only 6 months old so "should" be ok.

I was really focused on the #3 due to the code I kept getting so I figured I would pull just that one to see, and low and behold very oily. I replaced it with a spare plug I had laying around and it fired up and runs great. With that being said I am now more concerned about whats going on internally. I dont have an endoscope to look into the cylinders but just by shining a light and the naked eye its obvious the cylinder has carbon build up and looks shiny.

I did check my coolant and its low. Oil looks great and Im not getting excessive white smoke out the tail pipe. So I dont know.

At this point I have extra coils and wires laying around now. HAHAHAHAHAAHAAAA

With that said Ill be using it for my local grocery runs and to drive to work. I sure as hell dont trust it for any future long distance trips until I can have some one do a more thorough investigation than I can do.

Just thought Id share
Cheers
Curt

Excessive white smoke and low coolant do not sound good. Could be a busted head gasket, get cylinder pressures checked.

Just to clarify from my post that my coolant was low, but Im not getting excessive white smoke.

Top off your coolant to the correct level and monitor it for the next couple weeks. If it keeps going down, it's either leaking somewhere or is being burnt up inside the engine. Misfires can be a symptom of a bad head gasket.

A leak down test is the best way to determine if you do or do not have a bad HG (among other things).