PCV can cause cylinder miss fire

It would not hurt for you to change the PCV valve since it has 80K miles on it. However I doubt that is the cause of the engine misfire.

Did you have the iridium spark plugs changed at 120K miles? If not, they should be replaced now as worn spark plugs is a likely cause of engine misfire.

If the spark plugs had been changed recently, then check the spark igniter wiring harness connectors to make sure they are securely attached to the spark igniters. The fuel injectors and their wiring harness connectors are also suspect.

 

Are engine misfires supposed to happen on the Prius? My car has pretty much done some type of engine misfires since we got the car at 61,600 miles. The engine runs rough when the ICE is on and runs very rough sometimes shutting off the ICE. Other times it is completely or relatively seamless. Will the Check Engine light come on when the engines misfire?

I have noticed that even with the MAF and throttle body clean, the engine in my Prius still runs rough sometimes. I was told that the car running rough is completely normal by the Toyota dealership.

I notice when the ICE is running, the engine runs rougher generally than when only the electric only is on. It does more bucking/jolting when going from drive to park and vice versa, and I have noticed very abnormal unstoppable shaking two separate times when the car was in park.

 

1. The Prius has a four-cylinder gasoline engine and by its nature, is not particularly smooth-running compared to an inline six cylinder engine or a V-8 engine. Not only is an inline four cylinder engine not inherently balanced, but it only produces two power pulses for every 360 degrees of crankshaft rotation. Depending upon what you were used to driving in the past, you might think the engine runs a bit rough.

2. The check engine light will come on if engine misfire exceeds a certain % threshold which is relatively high. I think an individual cylinder has to misfire more than ~20% before a DTC will be triggered (which will turn on the CEL.)

3. Electric power alone will be quite smooth. It is to be expected that when the gasoline engine is running, more vibration and noise will be produced. The question of what vibration and noise is normal is somewhat subjective. You may need to drive another Prius for comparison purposes.

4. The issue of abnormal unstoppable shaking is unusual for 2G Prius. Neither my 2004 or 2007 had that particular problem, but I noticed it a few times with my 2001. It was just like a manual transmission car in first gear, if you approach a stop without pressing the clutch pedal. The engine will balk and jerk because it cannot spin smoothly at a very low RPM. If your car is producing that driveability issue, you might look into the possibility of having the hybrid vehicle ECU reflashed with the latest available firmware for your model year.

 

One possibility is that the center seam between the two pieces of plastic cowl covers that's leaking.

 

As I recall there was a Technical Service Bulletin for a leaky hood. If it has not been performed on yours a dealer will fix the gasket for free.

 

Usually because it rained so hard it overflowed the water seal on the water dam under the windshield and then it drips on the top of the engine and gets in the ignitors and rusts ignitor connections. Evidenced by alot of rust in the spark well. Usually requires a new ignitor to fix.

Btw, there's also a Gen 1 TSB for this includes new seal. If me I would check to see how the water dam evacuates also. Pour controlled water in the dam till it fills up but don't let run over. You should see a strong stream of water coming out for behind both front wheels. If not the dam vents are clogged with leaf debris. Pretty common. Always keep all debris out of that dam area.

 

Well, the cylinder head is a poor design and it bit you, but it's time to change the title of the thread because as you admitted, the PVC valve had nothing to do with a toyota misfiring, and as is it's misleading, jmho