Power Surging

[sjrainsford]

Hi all!

Am loving my Prius and have knocked up quite a few miles in it already.

One thing I've noticed is when doing 50mph for instance, and if I floor the throttle the car gets up to the legal limit much quicker than I was expecting. However, if I keep my foot down from 50 i've noticed that the power seems to come in surges rather than as one hit. So you get lot's of power, then it drops slightly, then get more power etc etc. Anyone else experienced this?

[Jan&tone]

Its not the noise of the cvt picking up and then adjusting itself to the speed of the car is it??

[Grumpy Cabbie]

Sounds odd to me. I know the gen2 and gen3 are slightly different but I find one continuous band of power right upto erm, motorway speeds.

Were you the owner with the dodgy 12v or was that someone else? What mileage are you at? Do you need the spark plugs changing? If your miles are getting high you might want to consider getting a Toyota dealer to change the transmission fluid - I think it is an unusual type but could be wrong.

[cootuk]

The most noticeable thing I notice is that you can be accelerating and the engine decides to change rev range (as it were) and you get a very slight surge as the engine changes revs. Not lumpy acceleration or anything, just a slight one off surge as everything switches round to meet your higher power needs.

[capnbirdseye]

I've not noticed that, I have noticed that when you want a sudden burst of speed there is sometimes a slight lag before it takes off which I think depends on whether the engine is actually running at the moment you push the pedal. So many drivers think a Prius is a milk float and can't wait to get past are probably astounded when you suddenly take off and leave them in the dust.

I had 2 kids in a chav boy racer car right up my boot ( really tailgating me) till we got to a traffic island where a dual carriageway started and they immediately tried to overtake me but had no chance probably due to their losing momentum with gear changing. Needless to say I left them so far behind that they then kept at a considerable distance even when I slowed down.

The 2006 spirit I had on loan for 3 weeks before mine was ready seemed to be a bit nippier and also quieter as regards to road noise, Two of the tyres on mine are from a brand that seems popular in the USA,-- DURA PERFORMA HP1, anyone heard of them? I think they are noisy

[sjrainsford]

Yep i'm finding that its got more go in it than the figures would suggest. I'm not sure what cars the reviewers drove either as I'm finding it quite refined on the motorway apart from road noise intrusion.

I'm very sensitive to car 'feel' though so its probably me just being over sensitive!

I'm not the one with Battery issues, although it is a 57 plate so the Battery is around 4 and a half years old. It's only done 34000 miles and feels and looks like brand new.

The only thing I've noticed is that the engine appears to miss fire when it is ticking over, especially when cold. It may not actually be miss firing, but you can feel a shudder from it quite regularly. Maybe that's pointing me in the direction of the problem.

If there is one of course!!

[capnbirdseye]

When you say 'a shudder' then that is a more or less normal thing with the engine turning off but only should be noticeable when stationary. Normally when coasting up to lights etc then the engine should have already turned off as per normal but if it's charging because you have maybe lights,wipers, heater etc then the engine might be on when you stop and it will indeed give a little shudder when it turns off. Strangely enough the 2006 model I mentioned above kept doing that but it was during the extreme cold before Xmas however but mine rarely does 'the shudder'

[Grumpy Cabbie]

If the 12v Battery is 4 years old I'd say you'll probably need to start looking at replacing it. The US forums are full of owners who have had big mpg drops, weird electrical gremlins and running issues when the 12v start to fail - usually 4 -5 years old. Many dealers will say the 12v is OK but it really needs testing after being stood overnight OFF or totally disconnected from the vehicle. A quick and basic test is to turn the car on (but NOT in Ready mode)after it has been stood overnight and then put all four windows down and then bring them back up - if they struggle your Battery is low on charge. Also, if you have run the 12v flat in the past can kill one of the cells inside and cause it to operate poorly from then on.

It is a weak 12v as it doesn't need to turn a starter motor etc - just fires up the Prius computers and lack of use such as in a low mileage car can kill it off early. I'm sure a Toyota fitted replacement is about £100 and well worth it for the peace of mind.

Perhaps Parts King or others can confirm the costings etc.

[agfs]

I paid about £70 for a new 12v Battery (supplied by the AA) after 35.5 k

[sjrainsford]

Thanks for the comments folks.

I know what shudder you mean with regarding the engine stopping or starting but it's not that. The engine is actually shuddering now and then whilst it's ticking over, when stationary almost like it's missing slightly. In my experience of past Toyotas though it's probably nothing.

I'm an electrical engineer so thanks for the heads up there, will give the Battery a drop test of some sort. I'm getting an indicated 51mpg but it's actually 5mpg lower than that really with all my journeys being over 15 miles I'd say that's not brilliant. So as you say this could be related to the Battery.

[capnbirdseye]

The 12v Battery apparently does more than just fire up the computers in the initial few seconds according to this:

My link

he refers to his job job at with automotive electrical systems and connected various testing equipment to come up with interesting results altho the attached PDF files he mentions are missing

[sjrainsford]

To be honest, if the Battery was only driving electronics with small inrush currents then it would be even smaller.

Basically it does everything a normal car Battery does aside from actually turning a starter motor. It still runs other motors though.

Anyway, I ran a few tests on mine yesterday and it seems fine. Plus the car is under a Toyota warranty so will probably get them to look at at. Currently I'm still trying to adjust to the fact that I don't work shifts any more and don't know when people who work a 9 till 5 day ever get anything done!