Cruise control slow to engage

My cruise holds right where I set it, just like my other cars. I get up to speed like you say, push the lever down to set, see the SET light come on, ease off of the accelerator and the speed stays right where I set it.

I would take it back to the dealer and show it to them.

Also, I single "bump" up or down changes the speed by 1 mph. If you hold it down I believe I have read where it increments in 5 mph steps, though I have not tried this.

 

Unless you are going up a hill at the time you engage the CC, I think you have a claim with the dealer.

 

I have noticed the same. A bit annoying in my opinion. The other cars that I have driven did not show that behavior - their cruise control took over immediately. What I do now is when I press on "Set", I wait for 2 seconds before releasing the accelerator.

2 years ago I had rented a Prius II, and I had noticed something similar.

 

I set mine often going up an on ramp and mine sets fine.

 

Are you in Eco mode? The CC will lag going up hill in eco mode and then catch up just as you're discribing. Make sure Eco is off and try again in standard or even Power mode.
Tom

 

i use eco mode and don't notice the op problem.

 

I confirm that the problem appears both in ECO and normal modes.

 

Yes it is normal, I don't think it is mode dependent. If the ICE (or catalytic converter) has cooled down the ICE will start to warm itself up even in reverse. It usually takes about 15 seconds after the ready light comes on. Emissions take priority over mileage. Also, you can start the ICE anytime by pushing your foot down on the accelerator in park.

 

I have also noticed something similar with the "resume" function. Sometimes, pressing on "resume" to go back to the previously set speed after a "cancel" can take as much as 4 seconds before the CC starts to accelerate. Anyone else noticed that?

 

I just found another anomaly with the cruise control.

This afternoon I have tried the technique proposed by nparker in http://priuschat.com/forums/gen-iii...conomy-hills-cruise-control.html#post1135178:

I have tried the same: I have set CC to 100 km/h, and when the car was going down a hill, I pressed slightly on the accelerator to start gliding, without cancelling CC. Then speed increased over 100 km/h. On the other side of the valley, speed started burning down. I assumed CC would take over as soon as speed went back to 100 km/h, as the other cars that I know would do. What happened instead is speed decreased down to 94 km/h before the CC decided to kick in and accelerated back to 100 km/h. I tried it twice and got twice the same result.

Anyone else observed similar anomalies with cruise control?

 

This sounds a lot like other cars I've driven too, though I haven't done it on the Prius yet.
In general, it seems to me like the cruise control computer (not Prius-specific) determines how far to press the gas pedal based on current speed and acceleration. It won't make sudden changes, so if you quickly go from flat roads to a steep incline, it will slowly press more on the gas pedal, but bleeding speed, until it floors the pedal and gets you back up to speed. It also doesn't know how hard you are pressing, and the engine control computer will take input from whoever (you or the CC) is pressing the gas pedal harder.

Relevant to this case, when you're going over the target speed, it will let up on the gas pedal. So you're pressing at 10% (eg) to glide, the CC computer is pressing at 0%. As you reach the bottom of the hill, you're still pressing at 10%, the computer is still pressing at 0%, and you start bleeding speed ever so slowly. Because the rate of deceleration is so slow, the CC computer will stay at 0% until just before you reach the target speed, and then it will slowly push harder, not reaching the same 10% that your foot is at until you're at 94 km/h, and then it will push even harder to get back up to the target speed. The car takes gas pedal input from whoever is pushing harder; you or the CC computer. So while the CC computer is figuring out how hard it has to press to exceed what you're doing, it feels to you like it's not doing anything.

I've noticed this on at least a Ford and a Honda before, so it wouldn't surprise me that the Prius does this too. I typically notice it not when gliding (since these weren't hybrids) but rather when passing somebody who is going ever so slightly slower than me; I accelerate to the speed of the fast lane, pass, pull back in front of them, and then have to transition back to CC without slowing down the person I just passed.

If you prefer a smoother experience, what you can do is start pressing harder on the pedal to keep the speed 1-2 km/h below the target speed. It might take longer for the cruise control to take over from you (because it sees no need to start pushing as hard as you are on the gas pedal to make such a small adjustment when it's not pressing at all), but it should eventually start pressing harder than you, and get back to the target speed.

 

Funny my '10 also does this... it does engage about about 1-2 seconds and come back up to the speed I set. Will just have to live with it.

 

I have experienced the same problems with CC. What I have found is that when setting the CC speed......bump the "set" twice. This is a very minor fix.....but seems to work for me.

 

Take it into the dealer.
Have them check for vacuum leaks.

 

The Prius cruise control doesn't use vacuum to operate. It's fully electronic with a throttle motor (the same one you influence with the accelerator pedal).

What all of you are describing is normal cruise control function. It's a feedback control system, and with too much "gain" will oscillate. So gain is reduced, causing perceived delays. Add to this the lower power of the Prius, compared to some other cars, and you get a drop of a few km/hr before it recovers from overspeed or sometimes when you set it. There is also a short time delay built in to ensure drivers don't panic and report the car "taking off"! As some have already done!!

This IS NOT a "problem"!

 

Just to add to the discussion, my Prius does the exact same thing as the OP. I have learned to live with it, and just not take my foot off the pedal as quickly. Seems to operate fine once it's engaged. I guess what I am saying (and I think this is confirmed by others on here) is that this is not abnormal behavior for the Prius.