Cruise Control Kickdown

[SeaDuck79]

When I have the cruise control on, the kickdown is VERY sensitive. Far more so than when I drive without the cc. Has anyone else seen this, and know of a way around it? It downshifts at small inclines - less than an overpass.

[johnnieliu]

When I have the cruise control on, the kickdown is VERY sensitive. Far more so than when I drive without the cc. Has anyone else seen this, and know of a way around it? It downshifts at small inclines - less than an overpass.

I HATE THE RX330 CRUISE CONTROL!!!

We just came back from a roadtrip from WA-CA. Going up and down the pass and hills was horrible using the cruise control. The car downshifts to 3rd gear abruptly, such that it felt uncontrolable and hazardous. This is very evident if you are going up hill on slightly windy stretch of freeway and much more evident if there was a slow moving trunk in fron of you.

We did the same trip last year in my Infiniti J30, and the cruise control was much smoother and didn't abruply downshift when trying to maintain speed on an incline.

[Rx300_coach]

i also experience this when i was in a dangerous situation and i need to give my rx300 full throttle...the car jerked forward violently(from the downshift)

and when i let my foot off the gas after i finished passing the car jerked again(upshifting i presume)

haven't tried the cruise control yet...

[mailrail]

Just got back from a 200 mile trip in my RX 300 and used the cruise control for most of the trip. A lot of it was hilly terrain. I only experienced downshifting when going up some VERY steep hills. I haven't seen this in the Lexus owner's manual (because I haven't looked) but most manufacturers don't recommend that you use your CC while driving in hilly areas.

We used to have a 2000 Mazda MPV van that would downshift TWO gears when going up hills with the cruise on. It would nearly red-line everytime it downshifted. I hated that thing!

[wwest]

Hilly areas, no CC...

Who started that rumor??

Maybe not if the hills are so steep the CC can't hold speed going up or down but otherwise I never heard of such a thing.

Unless you mean in slippery roadbed conditions and in that case you should NEVER use CC, on the flat or hilly.

And its possible the RX330 kicks down out of OD so quickly because the OD gear ratio is so tall the engine cannot deliver significant additional torque at those RPMs, ~2200RPM at 70MPH.

The torque converter needs to be unlocked so the engine revs can rise while maintaining the same roadspeed.

[mailrail]

Hilly areas, no CC...

Who started that rumor??

Maybe not if the hills are so steep the CC can't hold speed going up or down but otherwise I never heard of such a thing.

My mistake. I guess I was thinking of the SLIPPERY roads. Either that or my Mazda owner's manual said it. Nonetheless, I couldn't use it for hilly terrain in that piece o' crap because of the constant, annoying downshifts.

One thing I don't like about ToyoLexus CC (as opposed to HondAcura's) is that the cruise light is always on with Lexus (when you have the master control on) where the Acura only comes on when the system is actually engaged. Just a little less corn-fusing.

[SeaDuck79]

These were not slick roads or big hills - I would expect a downshift on a steep hill. What I REALLY expect is that a computer controlling the gas pedal will operate it at least as efficiently as my stupid foot does.

Why does that seem to be too much to ask?

[wwest]

Your foot isn't stupid, it has the definite advantage of your vision. You can take the transmission out of OD or even downshift it because you see an upcoming steep climb. The Transmission doesn't know about the steepness until the engine starts lugging down.

[SeaDuck79]

But if the issue was the engine lugging down, why wouldn't it downshift at the same RPMs under the same conditions whether or not the cruise was on? It's not even a close call now - it downshifts WAY before I think it should, and where it never would without it.

[wwest]

You asked the cruise control to maintain "65MPH" and it wants to do that within +/- just a few MPH. What is not apparent to you is that before the downshift the CC kept moving the throttle further and further open, all you NOTICE is the sudden downshift when the transmission ECU says "enough already!"

Without cruise control on, YOU are the one pushing the gas pedal further and further down (or letting the speed decline) and so you are fully prepared, mentally, for the "feel" of the kickdown.

My bet is that if you really pay attention going up a hill and try your best to maintain a specific speed you will find that "your" shift point is exactly the same as the CC.

[johnnieliu]

You asked the cruise control to maintain "65MPH" and it wants to do that within +/- just a few MPH. What is not apparent to you is that before the downshift the CC kept moving the throttle further and further open, all you NOTICE is the sudden downshift when the transmission ECU says "enough already!"

Without cruise control on, YOU are the one pushing the gas pedal further and further down (or letting the speed decline) and so you are fully prepared, mentally, for the "feel" of the kickdown.

My bet is that if you really pay attention going up a hill and try your best to maintain a specific speed you will find that "your" shift point is exactly the same as the CC.

My J30 will try to maintain speed on an incline at its top gear 4th. So the acceleation need to maintain speed is gradual and not abrupt like the RX330.

Also, the RX330 has a tendency to overshoot its set speed, disengage the throttle and cruise back down to speed, and then engage the throttle once set speed is met.

I think that the ECU is the culprit and not CC, and I think that its linked to the other "acceleration", "transsmission lag" problems reported on this and other boards.

BTW, I did have my ECU re-programmed per existing TSIB# TC005-03.

JL

[wwest]

J30, lighter, by a lot, lower CD, and more(??) or equal HP. Also, since this is an SUV extraordinary measures are done (TALL OD gearing, 2200 RPM @ 70MPH) to improve MPG.

[wolfie212003]

I have a 2002 RX300 and I recently bought a 98 honda Accord and one thing I like about the accord's CC over my RX is that it remembers the set CC speed after a complete stop (ie: at a toll booth or something) vs. the RX which resets apparently. I thought that was interesting.

Does Lexus do that as a safety measure or something so that someone doesn't accidentally hit resume and end up having the car suddenly surge on them when they don't want it to?

Just wondering.

[wwest]

On my 01 RX300 the only things that kill the previously set CC speed is turning the CC off manually or the ignition. You must remember to use "resume" and only after getting the speed up to the point where the CC will engage, usually ~35MPH.

[johnnieliu]

J30, lighter, by a lot, lower CD, and more(??) or equal HP. Also, since this is an SUV extraordinary measures are done (TALL OD gearing, 2200 RPM @ 70MPH) to improve MPG.

I get your point. I guess a better comparison would with an MDX, or FX35.