CDeLappe

I have purchased a 2005 ES 330 with 60,000 original miles. The problem is when using the cruise control ( indicator on dash works ), it will hold at set speed perfectly and will reset to a different speed properly, but as vehicle goes downhill it will pick up speed. I use foot brake to slow down if needed. otherwise when reaching level ground cruise automatically resumes set speed. What is my problem? Can this problem be corrected without dealer cost? I have some repair experience, just to save money really. So, is this a problem I could repair with proper instructions?

WILLYumD

So what I've gathered is that your car doesn't slow down when it goes down a hill?

That would make sense as cruise control usually controls throttle and not the brakes.

CDeLappe

WILLYumD Yes, you are correct. It will not slow down going down hill. Not a big problem, a nuisance. All other functions of cruise control work properly. Strange! I did not know cruise controlled did not control brakes, so I have learned from your post. Thanks

Oro

How much is it accelerating and on what grade hill?

While it does not control brakes (and you do not want it too; that is just another potential failure point to introduce into a mission-critical component), it does control fuel flow and I *think* timing to adjust speed. I live in western WA in the Cascade foot hills. Probably very similar to any hilly region of TN. I drive a lot of grades constantly and my car (2002) controls downhill speed very well. If it is letting it run away by more than 5mph, there are things to check out, but if it is within 2 or 3 mph you should not worry.

CDeLappe

Oro What conponents under the hood should be checked to repair the situation? I live in a similar hilly situation as yours. The speed will increase as much as 15 mph maybe more, as I apply brake for safety. Trying to not to have dealer cost.

speedkar9

Cruise control on drive by wire throttle cars controls the throttle and transmission.

Additionally, the 4ES transmission has a form of hill decent control (even if the cruise control is off, you can feel it working). With your foot off the gas, it downshifts for you to provide some engine braking. Once the vehicle slows a bit (not all the way to a crawl) it will upshift again and continue to pickup speed (which for me, gets annoying as the car lurches forward downhill).

So yes, it is normal for the car to start speeding up with cruise control as it descends a hill, but there is a certain degree of engine/throttle braking.

ES300NZ

I live in a very very 'hilly' area, cruise control in my 1999 will actually 'run away' down hill. Say if it's set to 100kph, I've seen over 120kph. You have to give on it, put your foot on the brake and re-set it when it gets to a flat area (

there aren't alot of those in Wellington, New Zealand, just feral hobbits and strange, tall, pale thin people with odd ears and fancy clothing wandering the hill sides with these horrible creatures chasing them. They mostly keep to themselves so no one's too worried about them.