Cruise Control

[EnginePassion]

Did anyone notice the reaction of the cruise control on hilly roads is too much to the degree I call it "jumpy" this even is not as smooth as a cruise control of a 1990 car. I hope I am the only one who experienced that and then I'll take my baby to the dealership before the warranty expires.

Thanks.

[NicLX470]

I think it's fine. The car is constantly trying to maintain the speed set at and when going uphill it will open the throttle alot more than you probably would if you were driving without the cruise and it downshifts quickly to maintain the set speed.

[LEXUS IS250 AWD]

I agree. If it were smoother trying to maintain the set speed you would have a higher lag time before the odometer gets to where you want it to be.

[GDixon]

The RX350 is famous (infamous) for this. It is like riding a bucking bronco.

[EnginePassion]

I agree. If it were smoother trying to maintain the set speed you would have a higher lag time before the odometer gets to where you want it to be.

=====================

I am pretty sure it'll spin on icy hilly roads if the cruise is on. Since you're in Canada, did you ever use the CC in winter?

I still believe it accelertes way too much, the weight of the car is part of the equation which tends to drag the car down and backward that's why it tries to compensate by letting too much gas in.

[EnginePassion]

The RX350 is famous (infamous) for this. It is like riding a bucking bronco.

===================

That's a good analogy; LOL.

It's very uncomfortable and not suitable if seniors or babies are on board.

[GDixon]

The RX350 is famous (infamous) for this. It is like riding a bucking bronco.

===================

That's a good analogy; LOL.

It's very uncomfortable and not suitable if seniors or babies are on board.

Here is a link to another post on the subject you raise.

http://us.lexusownersclub.com/forums/index...c=41598&hl=

[pauljcl]

The RX350 is famous (infamous) for this. It is like riding a bucking bronco.

===================

That's a good analogy; LOL.

It's very uncomfortable and not suitable if seniors or babies are on board.

Here is a link to another post on the subject you raise.

http://us.lexusownersclub.com/forums/index...c=41598&hl=

Good (so to speak) to know that I am not alone in this. I had noticed the same thing on my new (Feb.) 09RX350. As a result, I 'modulate the throttle' myself as I can to prevent the lunging that the Cruise Control causes. It is also wicked when you have had to slow down with brakes (thus disengaging the CC), and then click it to return the earlier speed. I now drive up to that speed and then re-set. It wasn't that bad on the old RX300, so why/how have Lexus screwed it up? [On my return from MI, I was going to ask the dealer if there was a way to 'soften' the acceleration' on CC, but forgot to do so.] [There should/MUST be a 'flash' of the ECU available to reduce this problem.]

[bartkat]

Maybe I don't get it. I don't have a problem. How steep and how long are the hills? I can go from here to Ohio through KY and TN mountains on cruise and if nobody gets in the way, never kick it off and have a very smooth ride. If I am on a regular road and have go stop at a light, I can hit resume at 20 mph and get smooth and acceptable acceleration back to highway speed. I once was passed by a truck going down the south side of a mountain. He was doing 90. I set my cruise at 90 and it maintained for me at a safe distance for several miles all the way into the valley.

Underpowered cars will, of course, downshift sooner on lesser hills as it tries to maintain set speed. That's how it works and what it tries to do. A CRV for instance will downshift as soon as it sees the slightest hill. You can see the speedo drop and in some cases it may never even recover speed depending on setpoint and the hill it's on.

Of course it's not recommended to use cruise on really steep curvy roads, wet hilly roads, and ice and snow ought to be obvious not to use to any driver with half a lick of sense.

[EnginePassion]

Well, it looks like this is another Lexus (not just the IS) design problem that I and other Lexus cars owners have to live with! I'm sure Lexus service managers will say this is pretty normal as if the normal of Lexus is very different from other cars normal!

[NicLX470]

Ok guys this is a totally normal function and not a design problem for any car with cruise control on going up a hill. Just think if you are driving without cruise and going uphill and the car starts to slow down. If you want to maintain the same speed you are going to have to press harder on the accelerator and most likely the car will up-shift if you are dead set on maintaining the same speed without going too far under. So either don't use the cruise or get over it. And to top it off the crappier the engine is in your car the worse the downshift jerk and the longer the RPM will stay high in a lower gear to maintain the set speed. I cannot fathom how so many people do not understand this.

[smooth1]

Did anyone notice the reaction of the cruise control on hilly roads is too much to the degree I call it "jumpy" this even is not as smooth as a cruise control of a 1990 car. I hope I am the only one who experienced that and then I'll take my baby to the dealership before the warranty expires.

Thanks.

Can you make the car smoothly downshift while not in the cruise control mode? on those same roads?

[GDixon]

Ok guys this is a totally normal function and not a design problem for any car with cruise control on going up a hill. Just think if you are driving without cruise and going uphill and the car starts to slow down. If you want to maintain the same speed you are going to have to press harder on the accelerator and most likely the car will up-shift if you are dead set on maintaining the same speed without going too far under. So either don't use the cruise or get over it. And to top it off the crappier the engine is in your car the worse the downshift jerk and the longer the RPM will stay high in a lower gear to maintain the set speed. I cannot fathom how so many people do not understand this.

Both of your cars are fairly high powered so can take some lugging. Your comments are not applicable to this discussion based on your models. It also has nothing to do with not understanding the concept.

The problem is a shifting action every few seconds on even moderate inclines. The car seems to cycle far too often in a surge (downshift) and lug (engine stall) pattern that is quite distracting and even disconcerting. The CC setting band between surge and lug seems to be far to narrow - like a home thermostat setting in a 1/10th degree band. It is to the point that, at least in my case, CC is not used unless on flat ground (as you imply).

BTW - my V-8 Ford truck takes the same hills with CC in overdrive without a single downshift.

When the RX is not in CC on the same roads it does not shift nearly as often to maintain the desired speed. The IS250 of the OP might experience the same circumstances. While engine HP is certainly a factor, with the CC engaged there seems to be a change the RPM shift points. Since this is electronically controlled rather than vacuum controlled it seems that a reprogramming could change the settings. Lexus may have programmed the smaller engines to do exactly what is being observed.

[bartkat]

I don't remember what car it was but i had one that you could stop at a light and then hit resume and the cruise would hit WOT until it reached set speed.

[NicLX470]

Ok guys this is a totally normal function and not a design problem for any car with cruise control on going up a hill. Just think if you are driving without cruise and going uphill and the car starts to slow down. If you want to maintain the same speed you are going to have to press harder on the accelerator and most likely the car will up-shift if you are dead set on maintaining the same speed without going too far under. So either don't use the cruise or get over it. And to top it off the crappier the engine is in your car the worse the downshift jerk and the longer the RPM will stay high in a lower gear to maintain the set speed. I cannot fathom how so many people do not understand this.

Both of your cars are fairly high powered so can take some lugging. Your comments are not applicable to this discussion based on your models. It also has nothing to do with not understanding the concept.

The problem is a shifting action every few seconds on even moderate inclines. The car seems to cycle far too often in a surge (downshift) and lug (engine stall) pattern that is quite distracting and even disconcerting. The CC setting band between surge and lug seems to be far to narrow - like a home thermostat setting in a 1/10th degree band. It is to the point that, at least in my case, CC is not used unless on flat ground (as you imply).

BTW - my V-8 Ford truck takes the same hills with CC in overdrive without a single downshift.

When the RX is not in CC on the same roads it does not shift nearly as often to maintain the desired speed. The IS250 of the OP might experience the same circumstances. While engine HP is certainly a factor, with the CC engaged there seems to be a change the RPM shift points. Since this is electronically controlled rather than vacuum controlled it seems that a reprogramming could change the settings. Lexus may have programmed the smaller engines to do exactly what is being observed.

First of all, everyones comments on here are applicable to any discussion. So slander on this board is not needed. I'd like to see how you know you are driving on the same grade hill as these other guys are in your Ford. And the reason the RX does not shift nearly as often as when CC is on is because you are not pressing the throttle enough for it to upshift. You are allowing a greater band of deceleration which is fine. But when CC is on, it wants to keep the speed set and will do anything it can to keep it there. Driving with your own foot and with the CC are two different animals and somehow I will get it through your heads. But anyway regardless this is a normal function of any car cruise control on or not. If you want to maintain a certain speed you are going to have to press the gas more and sometimes the car is going to upshift is my point...depending on the engines power and the amount of throttle you give it. But when in cruise it will only allow a certain amout of deceleration before it says...."hey I need to speed up". And if it cannot keep the current speed in the gear the car is already in it wll upshift and get you there the quickest way possible. So all in all the point is....this is completly normal. My tank LX470 does it with CC, my dads Dodge Ram with the Hemi does it with CC, it's all the same. But I can drive both of these cars on the same roads and be more sensitive with the throttle and they will react normal not trying to keep the same speed. Never has my IS350 done it though. It has enough power in almost any gear to maintain a speed even on some grades that I have driven on. But i'm sure there are some that would make it upshift. But I do not live in a hilly area. So if these "actions" by a normal functioning car bother your. Don't use the cruise. I understand that driving at a normal speed and then all of a sudden it upshifting to keep up the speed can feel like the car is going out of control without your input but hey, that is was cruise control is used for. So because my comments are "not applicable" i'm just going to tell you guys to get used to the way cruise control works. Or don't use it at all. You are not going to get anything done by complaining to Lexus about it.

[NicLX470]

I don't remember what car it was but i had one that you could stop at a light and then hit resume and the cruise would hit WOT until it reached set speed.

My first car!! Was a 92 Accord and I could do it with that car.

[bartkat]

I think it was the 72 Maverick with 302V8 in it. That thing was pretty fast and the first couple times it did that in cruise it scared hell out of me.

[GDixon]

Ok guys this is a totally normal function and not a design problem for any car with cruise control on going up a hill. Just think if you are driving without cruise and going uphill and the car starts to slow down. If you want to maintain the same speed you are going to have to press harder on the accelerator and most likely the car will up-shift if you are dead set on maintaining the same speed without going too far under. So either don't use the cruise or get over it. And to top it off the crappier the engine is in your car the worse the downshift jerk and the longer the RPM will stay high in a lower gear to maintain the set speed. I cannot fathom how so many people do not understand this.

Both of your cars are fairly high powered so can take some lugging. Your comments are not applicable to this discussion based on your models. It also has nothing to do with not understanding the concept.

The problem is a shifting action every few seconds on even moderate inclines. The car seems to cycle far too often in a surge (downshift) and lug (engine stall) pattern that is quite distracting and even disconcerting. The CC setting band between surge and lug seems to be far to narrow - like a home thermostat setting in a 1/10th degree band. It is to the point that, at least in my case, CC is not used unless on flat ground (as you imply).

BTW - my V-8 Ford truck takes the same hills with CC in overdrive without a single downshift.

When the RX is not in CC on the same roads it does not shift nearly as often to maintain the desired speed. The IS250 of the OP might experience the same circumstances. While engine HP is certainly a factor, with the CC engaged there seems to be a change the RPM shift points. Since this is electronically controlled rather than vacuum controlled it seems that a reprogramming could change the settings. Lexus may have programmed the smaller engines to do exactly what is being observed.

First of all, everyones comments on here are applicable to any discussion. So slander on this board is not needed. I'd like to see how you know you are driving on the same grade hill as these other guys are in your Ford. And the reason the RX does not shift nearly as often as when CC is on is because you are not pressing the throttle enough for it to upshift. You are allowing a greater band of deceleration which is fine. But when CC is on, it wants to keep the speed set and will do anything it can to keep it there. Driving with your own foot and with the CC are two different animals and somehow I will get it through your heads. But anyway regardless this is a normal function of any car cruise control on or not. If you want to maintain a certain speed you are going to have to press the gas more and sometimes the car is going to upshift is my point...depending on the engines power and the amount of throttle you give it. But when in cruise it will only allow a certain amout of deceleration before it says...."hey I need to speed up". And if it cannot keep the current speed in the gear the car is already in it wll upshift and get you there the quickest way possible. So all in all the point is....this is completly normal. My tank LX470 does it with CC, my dads Dodge Ram with the Hemi does it with CC, it's all the same. But I can drive both of these cars on the same roads and be more sensitive with the throttle and they will react normal not trying to keep the same speed. Never has my IS350 done it though. It has enough power in almost any gear to maintain a speed even on some grades that I have driven on. But i'm sure there are some that would make it upshift. But I do not live in a hilly area. So if these "actions" by a normal functioning car bother your. Don't use the cruise. I understand that driving at a normal speed and then all of a sudden it upshifting to keep up the speed can feel like the car is going out of control without your input but hey, that is was cruise control is used for. So because my comments are "not applicable" i'm just going to tell you guys to get used to the way cruise control works. Or don't use it at all. You are not going to get anything done by complaining to Lexus about it.

There is one in every crowd. :P Arguments for the sake of arguing are pointless. You prevail, I'm done correcting your assumptions and misconceptions. Let your own words allow others to infer your intentions and intellect.

Slander: Oral communication of false statements injurious to a person's reputation.

(Excerpted from The American Heritage Dictionary of the English Language, Third Edition Copyright © 1992 by Houghton Mifflin Company. Electronic version licensed from Lernout & Hauspie Speech Products N.V., further reproduction and distribution restricted in accordance with the Copyright Law of the United States. All rights reserved.)

[bartkat]

[NicLX470]

(QUOTE FROM GDIXON)

There is one in every crowd. :P Arguments for the sake of arguing are pointless. You prevail, I'm done correcting your assumptions and misconceptions. Let your own words allow others to infer your intentions and intellect.

Slander: Oral communication of false statements injurious to a person's reputation.

(Excerpted from The American Heritage Dictionary of the English Language, Third Edition Copyright © 1992 by Houghton Mifflin Company. Electronic version licensed from Lernout & Hauspie Speech Products N.V., further reproduction and distribution restricted in accordance with the Copyright Law of the United States. All rights reserved.)

(END QUOTE FROM GIXON)

I'm sorry you had to look the word up to understand it. You are trying to make a bigger deal out of it than it is. I got upset because you're trying to tell me my comments are not true and applicable because I do not drive the car the topic starter drives. Well that doesn't mean I haven't before. And I only told you it bothered me and that should be the end of it. I don't see how you thought that was an argument. It was a more detailed comment correcting your inaccuracy about me trying to help out on this board. So you seem to be the one who needs to get over it. I had already forgotten about it. You seem to be loosing sleep over it if you need to be pulling out dictionaries and acting like a 4th grader. So if you want to act that way it's fine. But it's still not helping you. Seems as if you are the one who wants to argue. But on the other hand I could care less about you or what you think is an argument. This board is not about that. It's about helping out people who have questions about their cars and that is all I am doing. You can keep your negative connotations to yourself. And you are right about your last sentence. I DO let my own words speak about myself and my intellect. And I guess now I can say the same about you.

[SW03ES]

Chill guys...

I've not had a problem when going up hills, mine will hold the same gear until it can't and then it will downshift and then shift back up at the top of the hill very unobtrusively. My dad's LS's were/are the same way.

What I do know is that in a situation where you have slowed down and thus aborted the cruise, hitting "resume" results in a WOT surge that I find very unnerving and that other makes of cars I've had did not do. The Prius is the same way, and it has no gears in the transmission.

I've been driving these cars so long, I just automatically speed back up manually and hit resume after I've already reached the previously set speed to avoid it.