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Discussion Starter · #1 ·
Hi everyone.

Two weeks ago I bought my first Prius, brand new. About 20 miles out from the dealership, the check engine light came on and I noticed it seemed to be running a little rough. A U-turn to the dealer, 20 minutes in the garage, and they say one of the O2 sensors is dead (I was glad to see that they were as disturbed by that as I was, the word "fluke" was used at least five times). That has since been replaced (fully covered of course) but I still feel that the engine is not running properly.

Unfortunately, I have never owned a Prius before, and I'm coming from a 2000 Jeep Cherokee, so I have no idea how a 2007 Prius is supposed to feel. I think the best description I can give is that (when the ICE is running) I feel like it has a pulse to it. Imagine what it would feel like if the engine was spinning very slowly but one of the cylinders was firing much more strongly than the others.

Is this something I need to tell myself to get used to, or is there something wrong?
 

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My 2007 does not have that problem and if it did I would return to the dealer and take a mechanic for a ride.
Particulariy since you had a problem with the initial ride from the dealer.
 

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Are you talking about when you are sitting at a stop with the engine warming up, or while you are driving. My experience (04) is that the engine runs a bit erratically during the warm up phase at a stop but not while the car is actually moving. After it is warmed up, the engine usually shuts off at a stop, with the well documented shudder.
 

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Discussion Starter · #4 ·
It definitely happens at a stop. I'm not really sure how long it takes to warm up so I couldn't tell you if the engine is still warming up at the time. Unfortunately, it's quite a bit harder to notice when I'm actually driving around since it's hard to isolate it from your standard bumps in the road. I think it's still doing it while driving but for all I know it's just a combination of the road, my paranoia, and the fact that any engine is going to produce some vibration when it's under load.
 

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I'm guessing that it's normal. If you are sitting at a stop and the engine is running, it is probably still warming up, or about to shut off, in which case, as I said, it runs a bit erratically compared to conventional cars and outright shudders before shutting down. I think it is almost impossible these days for an engine to run poorly and not have the OBD II system detect some fault and put the warning light on. The system is so sensitive to anything that can cause emissions problems it tends to have the opposite problem. That is, the light comes on when you can't tell that there is even a problem.

If you aren't sure you could take it back to the dealer and have them check it out or maybe you could drive someone elses for comparison.
 

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Discussion Starter · #6 ·
I think you make a very good point about the OBD II system, especially with so hi-tech a car. Also, having thought more about my driving I realized that most of my driving during the week is to or from school and/or work (both drive times less than 15 minutes) and it's been below 40F for most of the week. A friend of mine also made the reasonable point that if it all of a sudden gets much worse and damages the engine, I've still got many thousands of miles left on my powertrain warranty anyway, so I suffer no more than the inconvenience of driving a loaner for a little while.

Looks like the plan for now is to try not to worry too much but make sure it doesn't get worse. And as you both say, if it persists and I start getting too worried about it I can always just have the dealer take a look at it.

Thanks!
 

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SomeJerk said:
I think you make a very good point about the OBD II system, especially with so hi-tech a car. Also, having thought more about my driving I realized that most of my driving during the week is to or from school and/or work (both drive times less than 15 minutes) and it's been below 40F for most of the week. A friend of mine also made the reasonable point that if it all of a sudden gets much worse and damages the engine, I've still got many thousands of miles left on my powertrain warranty anyway, so I suffer no more than the inconvenience of driving a loaner for a little while.

Looks like the plan for now is to try not to worry too much but make sure it doesn't get worse. And as you both say, if it persists and I start getting too worried about it I can always just have the dealer take a look at it.

Thanks!
From your driving description and the outside temperature, it's definitely a cold ICE situation and nothing to worry about. It's normal for a cold engine. Once it's fully warmed up, you will hardly notice the starting or stopping, except for the worried look on your passenger's face (...it stalled?).
 

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The temperatures down here are quite a bit warmer than anywhere else right now so I may not be the best guide.

When I first leave my house, the engine starts and runs for about 45 seconds to a minute. It will continue to run beyond that if I am driving but if I come to a light after that first 45 seconds, it will shut off (and it's usually more abrupt than normal and at times, it feels like it is second guessing itself and almost shutting off, not shutting off, and then a few seconds later, it shuts off.)

However, if I come to a stop within the first 30 seconds, it is very rough feeling. The engine is running but it feels not right. I never had anything like this with my 01 but, was the 01 an Atkinson engine? Maybe that's the difference?

I do love that thermos though... Last night, I needed heat and it was warm in the first 30 seconds!
 

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The classic was also Atkinson, but slightly different timing.

I believe the reason for the shudder is to prevent hydrocarbon emissions from escaping the intake assembly. The Atkinson pushes some fueled air back out into the intake manifold, some of which is captured in the charcoal pack in the air cleaner. I believe the Prius is allowed to run with spark but no fuel from the injectors to purge all fuel vapors from the intake assembly. This would give the feel of 'running out of gas' shudder.

However, the shudder usually doesn't occur right away at a stop, especially if there is cabin heat demand that the engine isn't warm enough to supply. In the latter case, the engine would continue to idle normally.

How does the car feel during the initial warmup 7 seconds after powering up to READY? This is a normal idle for about 10-20 seconds in moderate temps. You might get some shudder at the last 5 seconds of it shutting down the ICE, but not before.
 

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Unfortunately, I hardly ever start the car and then let it idle. Once the ready light is on, I am moving so I am already moving before the ICE kicks in and it feels fine.

I'm sure many will yell at me for this, but I have never let my cars warm up any before driving. Even with the Lexus, I start the car and as soon as it's running, it's in gear and I am on my way.

With the Prius, I leave just as quickly, it just hasn't started the engine yet.

When I get to my first stop sign (two blocks away), if I have to stay stopped for more than a few seconds, it shudders a few times. It feels like it is thinking of shutting off but then chnages it's mind. Two more blocks, I come to a stop light and if I have to stop there, it almost always gives a good shudder when it shuts down. From that point forward, it's fine.

I'm sure it's nothing....

One benefit to owning a hybrid.... I was driving up to Boston last June in my friends RX400H and I had driven too long and couldn't find a reasonable hotel so I pulled into a rest area, left the car in Ready, and went to sleep. A/C kept me comfortable for the 4 hours I slept and the ICE only started every 20 minutes or so. My gas mileage was still 25MPG for the entire trip up and back... Not bad for an SUV.
 

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Discussion Starter · #11 ·
DanMan32 said:
The classic was also Atkinson, but slightly different timing.

I believe the reason for the shudder is to prevent hydrocarbon emissions from escaping the intake assembly. The Atkinson pushes some fueled air back out into the intake manifold, some of which is captured in the charcoal pack in the air cleaner. I believe the Prius is allowed to run with spark but no fuel from the injectors to purge all fuel vapors from the intake assembly. This would give the feel of 'running out of gas' shudder.

However, the shudder usually doesn't occur right away at a stop, especially if there is cabin heat demand that the engine isn't warm enough to supply. In the latter case, the engine would continue to idle normally.

How does the car feel during the initial warmup 7 seconds after powering up to READY? This is a normal idle for about 10-20 seconds in moderate temps. You might get some shudder at the last 5 seconds of it shutting down the ICE, but not before.
I tend to only get the shutdown shudder the first or second time it shuts the ICE down when the car is cold. My concern is more how it feels while just idling (and occasionally accelerating). I would say it's more of a pulse than a shudder at that point. I think the more car-literate term might be knocking.
 
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