I have a big issue- 2012 Prius c slipping/jerking at slow speeds

wow - that's a hard one to shed any light on without actually seeing the vehicle in person. What came to my mind first was possibly not having the lug nuts tightened fully. But I'd think one of them would have fallen off now if that was the case. Have you tried putting the tires back where they were initially?

 

Tangential to your jerking issue, I know, but I couldn't help noticing:

Are you getting four new tires, or two new ones that you'll be putting on the rear?

In general, you never want worse tires on the rear than you have in front. I would probably have recommended not moving the tires (so just leaving the better ones on the rear) while waiting for the new ones. Then if it's four new ones you're all set, or if it's two new ones, put those on the rear and move the better old ones to the front at that time.

 

Broken CV joint?

I can't think of anything else that might do this on a c, but then I haven't seen one with 250k miles on it yet.

 

I think the issues might be unrelated; on general vehicle stability, you're better off with the good tires on the back, bu either way I'm not seeing that as the cause of the jerking you're describing.

So the engine was changed 150,000 ago? How did the transmission input damper look at that time? Was it reused, or was there one on the replacement engine?

 

Worn tires can do something like you describe. To me it felt like the tire was binding somehow, but I only noticed it at slow speeds and tight turns (i.e, parking lot) where the wheel would jerk a but a few times as I'd do a 90 degree turn. I'd never had a car do that before but I figured it had to be something about the c and the worn OEM tires (bought used with almost 50K miles on it) even though they seemed to be worn evenly and no feathering. It drove fine otherwise including high speed around curves. Once I replaced the tires a couple months ago it has not done that.

 

You should watch the video that was in that post.

 

That's what I think too but the current crop of "experts" doesn't agree.

While it is true that loss of traction on the front wheels is much harder to learn to deal with than loss of rear traction...........
your average driver is MUCH more likely to put the rears under "traction stress" than the fronts.
So it is more likely to have the rears lose traction so the ones with better grip need to be there.

I have been convinced that general situation is real enough so that conclusion makes sense.
But not for me. I still put the best ones on the front.
Because during my driving years I have recovered from a rear slide out maybe a thousand times with no major damage.
I have lost front traction twice. Both times required major body work.

 

As I understand it, whether that is true may be the exact thing being reconsidered by the current crop of experts.

"There are two good things about having the better tires on the back," noted Evan Sanders, another Michelin test driver at the proving grounds. "The main thing is that [the front tires hydroplaning] is easier to control, it's safer, it's more stable and the car won't spin out,"

Without doubting that you had the experiences you had, it's possible they involved factors that make them harder to generalize.

 

Which is more important, the traction you were hoping for or the traction you were counting on?

Always put the deepest tread on the back. That gives you the stability and steering control* you've been counting on the whole time.

*More precisely, it helps your chances for maintaining that control and predictability when driving in wet weather.

 

While seeing the logic there, it seems to me that this practice almost guarantees that the front tires need to be replaced earlier than the rear ones. This may result in different types of tires on a car.

 

Yes, you're bumping up against the lack of sophistication in a simple "more tread rear" rule. Like everything else, it is nuanced.

You're likely to wear the fronts faster in any car with F>R weight distribution.

Braking loads will amplify this a bit.

You can use regular tire rotation to keep things manageable. Yes, you will regularly wind up with a slightly deeper tread up front, but not for long as it wears. Doing it this way keeps all four tires at about the same performance for predictable handling throughout most of the life of the tires. It's just those periods right after the rotations where things are out of whack, but only slightly. Rotating the tires isn't the corrective action, just the setup: driving those first 500-1000 miles on them after the rotation is the real corrective work.

You could better honor the "deeper tread on the back" rule by installing 2 new rear tires, drive x miles and then move them to the front and put 2 more brand new tires on the back, and repeat ad infinitum.

The problem with that method is that the wear-induced handling characteristics of the fronts will be significantly different from those of the rears throughout most of the tires' service life. This isn't necessarily bad, just... undefined, not proven or predictable.

 

It doesn't SEEM like a misfire to me based on your video, but your plug change (along with the other thread) is strong circumstantial evidence of an ignition issue. Odd that it is not that consistent or throwing a code though. The occasional "rattle" just sitting at idle makes it seem like something is loose so inspecting the engine/transmission mounts wouldn't be a bad idea. I wouldn't think it would have to do with the transmission internals since it does it in park as well.

 

You didn't put any "grease" on the plug threads when you installed them, did you ??

 

Okay that's....kind of a big omission.

Put new plugs in the car. Buy good Densos from your neighborhood auto parts store. Amazon, eBay and most of the rest of the internet are overrun by crappy counterfeit plugs, so don't trust anything mail order.