engine seems to run roughly

I test drove quite a number of 2009 before I bought mine and I would say the engine should not run roughly, at least not for more than a few seconds - in some conditions when the engine shuts off or starts up you may feel the "rough stop" or "rough start", which are normal, but if the engine runs roughly continuously while the car is moving at speed then that does not sound normal. Just my 2 cents. Good luck!

 

If you're not seeing any malfunction indicator lights (check engine and/or a big red triangle), then it probably isn't a big problem.

But it really shouldn't be running roughly after warmup..

 

The faster and slower behavior you're encountering when engine warming up is normal on the Prius. Yes, it runs roughly during that time and RPM goes up and down. IIRC, it corresponds to stage 1a of http://priuschat.com/forums/attachm...ference-aid-priusstagemodereference051408.pdf (from http://priuschat.com/forums/knowled...perating-mode-availability-reference-aid.html).

I have a ScanGuage and can definitely see IGN at -10 at startup. But, I don't usually leave that gauge up nor monitor it anymore, for most of my drives.

The rough ICE shutdown that 2009Prius mentions can be a bit startling and sometimes very rough. It can almost sound like the car is dieseling (like the knocking sound you hear from overheated cars right after they've been turned off).

 

I know the feeling, it feels like it misfires or a jerking. This is normal and it does not feel like thart all the time. To my surprise, my 2007 has not gave me that feeling yet. What's weird is that yesterday on my way to the park, I set the cruise at 43mph purposely so keep the engine running at an efficient manner so that way I wouldn't run the battery down and induce the engine into heavy charging. Anyways, I was cruising at 43mph and my Energy Monitor was telling me that the engine was purely powering the wheels, while also sending charge to the battery. This is a fairly normal operation the Prius will select while cruising and I was getting between 53-57mpg. (As you might have seen from some past pictures, I live in the flat lands of IL. No hills at all.) Back to my story, my battery had 6 blue bars which is usually where the Prius feels most comfortable so it was fairly normal. About 5 minutes later, I looked back at the Energy Monitor, this time I had 7 green bars "Hmm, it must have charged more than it wanted." So I expected the car to start using more electric and for my mpg to climb, nope. She kept on charging. I kept a close eye on the SOC (state of charge) and before I knew it, BAM!, all 8 green bars where there! After it hit all 8 bars, it used EV mode very aggressively, even though I had my cruise set at 43mph. I took some photos of this event and will be happy to share them with you. Apparently, it's a battery reset of some sort that the Prius does every few thousand miles. I don't know if any of you have experienced this, but yeah.

 

Hey, that's what were here for.

 

One more reply "The engine seems to run roughly, especially ... when it goes up to about 45mph". What if you sit in park and rev the engine? Is that the roughness you're talking about or is it possibly from feedback via the tires and suspension while moving?

If one is used to the superior NVH (noise, harshness, vibration) levels from inline 6, V6 or V8 engines of non-sports cars, esp. luxury cars or family cars, then the NVH of 4 bangers like in the Prius will be disappointing. It's not just the intensity of the noise, but it's also the sound of it. I can totally relate since I miss the power and smoothness of my 02 Maxima's 3.5L 255 hp V6.

Maybe you can meet another 2nd gen Prius owner in the area and have him ride along or swap cars briefly and compare notes? I'd offer to except I'm on the other side of the country.

 

I'd start with changing the oil.

If you don't know the repair or maintenance history, this is cheap insurance. Mine *seems* smoother and quieter on synthetic, but I suppose it could be my imagination.

It wouldn't hurt to check the electrical, too, to be sure everything is functioning within normal parameters.

Plus, I'd highly recommend new tires. They're a small percentage in cost of the car, yet they make a huge difference in performance and safety.

 

Check the tire pressure. There are some threads about Prius tire wear and inflation pressure. The general consensus is that the Toyota specified 35 psi does not seem enough to keep the tire from uneven wear so slight over inflation is recommended. Some use 40 front 38 back and others 42-40. The max is specified at 44 for the OEM tires. Good luck!

 

OEM is pretty common - it means "Original Equipment Manufacturer"... so, if you buy a Toyota oil filter, you are going OEM with the filter... etc.

 

Google is my friend. The first item I got when I typed in "oem":