Mechanics

ROUGH RUNNING

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!
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Smcgann92562@yahoo.com
April 16, 2011.




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

Tiny
Rasmataz
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.

Thanks
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Tiny
Spreacker
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.

Rivermikerat
Sep 22, 2011.

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