engine buck wildly when first started

You guys realize that the engine is constantly starting and stopping for short periods of time in normal operation, right?

Would this not kill the theory of short trips causing the issue?

-Iain

 

I like your theory, but folks are saying it happens during cold starts.

 

Correct, it has only happened to me when I start the car from cold then shut it down within a minute or two the day before.

For example: I relocate it in the driveway when the engine is cold and shut it right off, then the next morning when it is first started it will sometimes do the "rough start" trick.

That is why it is hard to analyze, it only happens intermittently under a very special set of circumstances. Also as far as I know it mostly happens in cooler weather, not in the summer.

 

It hasn't been above freezing for months here, so I'll try your theory out.

Is it repeatable?

-Iain

 

No, unfortunately it is not repeatable. You could try to duplicate it for a week or two and it might not happen, also I think some cars don't have the problem. But I have never seen it in the summer or when I shut the car down after it is warmed up.

It doesn't actually need to be below freezing, first time it happened to me was in October and night time temperature was probably 35 to 40 or so. But the cars are apparently not all the same and others may have different observations.

 

we have not had it happen in our 08 with 40,000 miles. i wonder if they were able to fix it?

 

LOL, a ton of us have had this now but while at a dealership looking to buy it that is rich. It is a very rare occurrence and seems to only occur after the car was previously moved a short distance and stopped well before the engine reached normal operating temperature.

It "appears" like it's really nothing to worry about, but we don't know because Toyota hasn't said a thing about it that I've come across. I don't worry about it much. I've had it twice in 19k miles.

I agree you should. It is unequivocally a fault in the design somewhere. BTW, even among the times I do move it without it warming up it hardly ever makes this sound.

No, because when it is starting/stopping it's not shutting down cold. It's the shutting down cold that causes the problem. Though it is hard to repeat consistently at all, but you move the car a short distance and the ICE starts but way before it's warmed up you shut the car down and then let it sit for some hours/overnight/whatever, then you MIGHT get the sound after. Probably not, but it appears to be the only time people get it after a cold shut down.

I've not come across anybody able to consistently repeat it. I tried myself in conditions I felt would be perfect (started it, ice turned on and I floored it then shut it down immediately and then came out many hours later) and could not get it to recur.

 

I had mine do this when I started the car this morning...

And I think I can attribute it to the fact that I was reading up on the warming up stages and I wanted to test out the "stage 1a" (I think) that is supposed to run from the initial start of the engine to about 50 seconds later. My car was in the garage for about 4-5 hours and I thought I would time it to see how long it took for a noticeable change in engine sound (when the ignition timing enters normal range). So I started the car, timed it (about 55 seconds), and then shut it down.

When I started it this morning, it bucked for about 2-3 seconds and settled down. Maybe the unburned fuel theory does make some sense after all!

Could it be possible that in order to duplicate the problem, you have to let the engine run long enough to get out of the "Stage 1a" warmup phase, then shut it down (about 50-60 seconds from ICE startup - depending on outside temp and coolant temp)?

Edit: Rephrased last paragraph.

 

This happened to me this morning. It lasted for about 30 seconds and sounded just like in the video - very rough and banging. And yes, my 2010 Prius is red!

I came back from Florida last Sunday, so the car had been driven for 2 days. It then sat in my driveway for 4 days. The temperature has been below freezing on Long Island. It was not shut down cold, but hot, so it is not the case that it only happens with cold shut downs. Car has 22,000 miles and this has not happened before. Never happened with my 2005 Prius. I was thinking it might be contaminated gas, but I see that others have had this problem. The engine smoothed out to normal after 30 seconds. I hope this is not a serious problem. I usually start the car every day, so I wonder if sitting for 4 days has anything to do with it.

 

A google search reveals that this problem is widespread. Toyota must be aware of it. Is there any explanation of it so far?

 

No. Toyota is doing a good job steering clear of acknowledging it.

 

This is very disappointing. I like the gen 3 Prius, but it has problems I never have with my gen2. The brakes make annoying pumping/barking sounds. And now the rough starting engine that nobody has any idea as to the cause. I'm beginning to think the gen3 is worse than the gen2.

 

One thing I forgot to mention when I had a rough start this morning was that the engine came on immediately the second I pressed the power button. It did not take the 10 or 12 seconds it usually does.

 

Add me to the list of people that it happened to. (twice, with only 2500 miles on her). I did not see that poll, but you can add me to the 55%.

 

I went to the dealer and of course everything was normal. I faxed Toyota and they sent a letter offering to discuss this over the phone. Smart. No written record. Anyway, it only happened once so far so we will see.....