My 2011 Prius will start to stutter and shake when I have the pedal depressed just past halfway. It is way worse when it rains. Speed has no bearing on the issue. I added fuel treatment and premium fuel hoping that it was just bad gas but that did nothing. It has approx. 148k miles. No check engine lights or loss of fuel economy.
Check oil level and see any oil burning issue. From my experience, if the engine is not smooth, and there is no check engine light, mostly i will check the oil level and see if it normal or it's dirt or not. Also check other maintenance item, like air filter. I always change my oil on time. but I forgot to change my air filter. I just replace a new one over the weekend, the car is so much smoother and better MPG.
Welcome to Prius Chat . At 148 k miles: Have you done any preventative maintenance (PCV valve, egr circuit cleaning, intake manifold, etc)? How long had the shuttering phenomenon been occurring? Any oil consumption? Keep us posted .
There are threads here regarding stuttering and shaking when it's cold and damp out. I've had this issue on my 2011 (at 70,000 miles) and took it in to the dealer. Even though the engine light did not turn on, there was a code that registered (P0301 - misfiring cylinder 1). Dealer said the intake manifold needed to be replaced. Replaced it, but the problem did not go away. Dealer then said it was likely EGR (see this thread: warranty enhancement; P0401 EGR Valve | PriusChat). They replaced the EGR under this enhanced warranty. This was done just as the weather was warming up, so I don't know if it solved the problem or not. Now that we're getting into the cold and damp weather, we'll see if it fixed the problem. You might also read this thread: NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10 | PriusChat
I wonder: did they replace the EGR valve and the EGR cooler, or just the valve? The're part numbers 3 (valve) and 7 (cooler) here: EGR System for 2015 Toyota Prius | Toyota Parts
Aren't we skipping something cheap and obvious? Spark plugs. That and moisture in the plug tubes. I've replaced plugs twice and dried out ignitors twice (remove, wipe off, wait, reinstall) to clear a miss (which is also a stutter) in the 150K I've put on my 2004 - now at 342K. This is one of the EXTREMELY FEW faults I've experienced with this '04, the most trouble free car I've ever owned. If moisture is an issue, the bottom of the ignitor will be visibly wet. Simply throwing a $20 set of plugs at it is not excessive if they have 80K miles on them. On the other hand, this will usually throw a P0300 (or P030x where x is the cylinder with the miss) code. If you can drive over five minutes with the miss and DO NOT get a check engine light, I may all wet. As it were.
IMO, the misfire getting worse in rainy conditions strongly implies water infiltration into either the low or high voltage parts of the spark plug circuit. I would check the feed wires for cracking that would allow water to temporarily short out the circuit as well as the igniters and the seals around them. If you find water/moisture, either replace or dry out that component , and then consider how to ensure that the water-proofing of that component works more effectively .
