2002 Toyota Prius • 4 cylinder FWD Manual • 145,000 miles

My prius runs smoothly when it's cold and most of the time when it's warm. There are times when I pull over and go into a store and it's will run really rough for about 5 minutes of driving. The engine light comes on and gives a random misfire code. I took it into a mechanic and they found fuel in the number 1 and 4 cylinders. I had the injectors cleaned and inspected and the first time that I ran it and then stopped for 10 minutes it started misfiring again. The odd thing is that I can disconnect the spark plug wire on any cylinder and it will run fairly smooth. I'm confused!
April 16, 2011.

P0300 Random misfires normally caused by vacuum leak and bad fuel fuel-

Apr 16, 2011.
Would that cause it to misfire when it's warm but not when it's cold?

I am having the EXACT same issue with my 2002 Prius with 140000 miles. Did you ever find a cause? I had mine in the shop for 3 days and they replaces the o-rings on the fuel injectors because they appeared to be leaking some fuel, but it did not solve the issue. I have cleaned the mass air flow sensor and throdle body. I replaced the plugs last year. The only othe issue with the car is that the A/C only works for a little while and the green light stops flashing and it stops cooling. I assume this is unrelated but thought I would share as much data as possible since this is a tough one to solve.


Sep 3, 2011.
As the spark plugs heat up, their resistance increases. That could cause it. It could also be a vacuum leak that doesn't happen until the leaking part heats up and expands. Try running a can of good quality fuel system cleaner through your tank, change the plugs and wires, and check to make sure the coils) is/are functioning properly once heated up.

Sep 22, 2011.