Hi, I have a 1993 Toyota Pickup Auto Trans with the 3VZE V6.

I am having trouble getting the truck to idle smoothly and i seem to be down on power and mpg. When cold, the idle is high as it should be and it idles smooth and stays, for the most part, at the same rpm. However, when it gets warmed up and to operating temp the idle jumps up and down randomly and has a pretty consistent misfire. From standing at the end of the exhaust, the misfire sounds like a thump and when it thumps i can feel a burst of more exhaust come out.

The things I have replaced are:
O2 Sensor
Spark Plugs
Spark Plug Wires
Distributor Cap
Fuel Pressure Regulator (Unrelated)

I am sure there is more that i just can’t think of at the moment

The misfire doesn’t seem to happen when it’s cold and it also doesn’t seem to happen in drive, It only seems to happen in park idling. Or at least that’s when i have noticed it. Also while driving i don’t feel it want to stutter or hesitate, it just lacks power especially once at about 35 mph. I have run a little bit of sea foam through the intake plenum and that didn’t seem to do much, as i expected.

So i am wondering what i could do to maybe solve this issue without tearing too far into the engine or pulling the engine. Could it be head gasket failure? Clogged cat or clogged fuel filter? Out of adjustment or bad TPS? Out of spec valve lash?

I have not done a compression test but that is on the list. I am stumped and any help would be greatly appreciated

 

Spark plugs, wires, or coils. Easy stuff to chek. Move one item at a time to another cylinder, like say the spark plug, and see if the code follows it. If not, try the plug wire. Still no? Try moving the coil.

Just my thoughts.
Pat☺

 

Follow Pat's advice. I had a similar issue on my 88 3VZE and it ended up being a faulty igniton coil.