krawfo

I just finished my first road trip with my GS and noticed a strange cruise control behavior. When going down moderately steep hills, the cruise control would alternately speed up and slow down in a herky-jerky fashion.
Is this normal or do I have a problem?

SW17LS

It's normal for this particular car unfortunately...

nealb

I agree

I just did a round trip from TX to FL

going down a hill the car doesn't coast and gain speed

I believe that instead it shifts down to try to hold the set speed

the shifting up and down is the jerky stuff

SW17LS

As I said in another recent thread, the downshifting isn't the issue, its the way it rhythmically shifts back and forth that creates that "see-saw" type feeling.

I've owned many cars, and driven them in the mountains on highways using cruise control and I've had cars that hold their speed well on cruise when going down a grade and cars that don't...but I've never had a car that behaves in this situation the way the GS does...including my 4 previous Lexus sedans.

krawfo

Yes this is definitely a step back. My 2nd gen. G300 never did this. If this is the car's only flaw I'll be happy.

SW17LS

One of very few flaws! Its a great car

Joeb427

iTrader: (1)

Odd thing I've posted about before.
Said to be normal. .

r2xj

I haven't had the opportunity to test this on mine yet, but if it has this problem, you'd better believe I'll be calling Lexus! Anyone else with the overdramatic jerking should too, I doubt it would take much for them to issue a TSB to reprogram the shifting algorithm in cruise.

SW17LS

Its not "overdramatic", its subtle its just unusual feeling and looking when you watch the RPM needle.

For instance the passenger would probably not even notice.

Joeb427

iTrader: (1)

True.
You do feel it slightly but you see the tach needle drop a bit and stutter.
Just odd as this never happened with any other Lexus or other brand for me before.

SW17LS

Yeah it definitely feels wrong...

r2xj

It seemed that some felt it was a stronger jerking than that, but I'd have to agree that if a passenger couldn't even feel it, perhaps it is the intended response. Guess I'll be going for a nice drive up (and down) the canyon tonight!

r2xj

After taking my car down several different grades with cruise control on, I don't see what it does as an issue. Whether or not my car is doing the same thing as those with complaints, I don't know. It acts in a similar manner as my ES did, but the shifts are "sharper." I do think the passenger would easily feel these shifts, but it didn't seem excessive or out of the ordinary to me. It also felt like the shifts were a bit different depending on what mode I was in (i.e., sport, normal, eco), but that may have been in my head.

SW17LS

It's a rhythmic back and forth up and down shift. Never felt anything like it in either of my ESes