I'm not aware of a wide-spread problem with cold-start, engine knock in the 1.5L Prius but we're trying to characterize what it takes to reproduce the 1.8L Prius, cold-start, engine knock. It is intermittent and rare but if we can come up with a protocol that reliably reproduces it, we have a chance of getting effective, corrective action. If you've had the knock, recently, please take the poll and add any additional details including your model year that might lead to reproducing this problem at will: Reproducable knock? | PriusChat Thanks, Bob Wilson
Very occasionally my 2009 Prius makes loud banging noise when the engine stops at the end of S1 in Park. No apparent pattern.
Thanks! This sounds different than the cold-start problem we're seeing with the 1.8L Prius. But it is interesting, none the less. Our 2003 Prius doesn't knock but if I do the following: level side street 45 mph, engine is on shift into "N" and coast down to below 41 mph shift briefly into "D" and back to "N" before engine halts -> I'll hear and slightly feel the engine shudder to a stop, no knock In your case, I'm wondering if the 'parking pawl' might be loose. If the car is in "P", do you hear a knock if you try to rock the car back and forth on a flat surface? Thanks, Bob Wilson
You guys are scaring me...lol. My 2007 has never knocked or made any engine noise. Yeah, in the early stages before its fully warmed up it starts and shuts off harsh sometimes but it doesnt make any kind of noise associated with it.
I tried to rock the car in park in several different locations and no knocking sound at all. And I am pretty sure the noise I heard before came from the engine.
Bob, Just like other Gen 3 owners have reported here, I experienced the cold-start knocking with my 2010 the morning after after shutting down the engine with only a few seconds of run time while moving the car in my driveway. (EV isn't available with a cold engine below about 60 degrees.) Ambient at the time was maybe 30 degrees. The car then sat overnight. Upon start-up the next morning, I got a few seconds of the rough-running routine where the engine felt like it was trying to swap pistons. It's only happened twice in over 2 years with the car, and thanks to PriusChat, I now know to let the car run long enough to turn itself off. I'm not conversant about the several stages of warm-up, but it appears that the Gen 3 doesn't like to be interrupted while in the first stage ("warm-up interruptus"). Whether due to moisture in the intake manifold or confused programming, a start-up in cold weather after a short run time the night before may result in the automotive version of delirium tremens.
My 2012 had exactly these symptoms yesterday. ~30deg outside, did a quick move of my car in the driveway and shut it off, then had a rough terrible start the next morning. I'll let it complete the startup cycle next time!
Sometimes, even 10 minutes of sitting after letting the engine run for a few seconds cold will generate the knock and pending codes.
