Cruise control over compensates by 5 mph

2013 DCLB 4.0 auto. when i set my cruise control it will over compensate when i go over a bridge. ill have it set at 55mph and when im at the top of certain bridges it will have either down shifted to 4 or unlocked the torque converter and sped up to right around 60mph.

is this normal for others out in TW?

if it doesnt down shift, it doesnt speed up otherwise

 

If you are saying "at the top of certain bridges" I'm going to assume you are travelling on a peaked bridge, not a level one.

If that is true, then the truck needs to kick it down a gear and accelerate to maintain the setting you originally had while going up a grade.

 

Normal.
The cruise can't "see" the rise in the road and it can't react quickly enough to prevent speed overruns and underruns... It simply sees the truck slowing down, and the ECU tells it that the engine is under a high load, indicating climbing a hill or bucking a headwind, so it applies more throttle.
When the load lightens as the road flattens, it reacts, but it can only react after it sees that the load has lightended and the speed has exceeded the set speed.

Every cruise on the planet does this. Some are worse than others. It is one reason that cruise should not be used in traffic or in hilly terrain, especially curvy mountain roads.

 

This^

I always felt like cruise on a hill would destroy my transmission. Not sure if it will but don't like it being so jumpy. Cruise on level terrain only IMO.


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Maybe ever cruise control with an automatic, cruise works perfect with manual transmission every time.

 

Normal for the Tacoma. Our cruise control is especially bad. It's slow to engage and slow to respond to terrain changes. I've commented on this in the past and was reminded it's a truck; I shouldn't expect more.

 

Every Camry and jeep I owned did it

 

thanks for the input. first auto i have owned, so my cruise control on my ford ranger of 10 years was my right foot and it was a manual. guess i was just surpised at the over compensation. i knew it would down shift but didnt expect the acceleration.

i live in FL so not too many bridges. i started engaging the CC after the larger bridges that it does this on near the beach

 

it didnt just downshift, i expected that, it went from CC set at 55mph downt to 53mph ish up to 60mph ish then eventually work its way back to 55mph.

sounds like this is normal though. guess ill just use my right foot

 

Yup... it dropped to 54/53 and added more throttle, still saw a loss in speed and increase in load to it downshifted, which immediately throws the engine into the middle of the torque curve and results in a quick jump in speed.
If you're lucky, that's it... it'll settle down back at 55.
What normally happens to me on longer hills is a repeated series of up/downshifts... at which point I just add enough gas to hold it slightly above the set speed until I hit the top of the hill.

 

Generally when climbing a hill with CC on, I'll turn off O/D to keep the trans from shifting up and down constantly and to maintain a more constant speed

 

If I think of it before I hit the hill, I'll give it a little extra and get a "running start" on the hill, gradually releasing pressure on the gas as I climb the hill, with the goal of hitting the summit at the set speed.
Saves gas and nerves that way if I can time it right to avoid any downshifting.

 

Normal for the Tacoma. Our cruise control is especially bad. It's slow to engage and slow to respond to terrain changes. I've commented on this in the past and was reminded it's a truck; I shouldn't expect more.

X2

 

My truck does the same thing and I absolutely hate it. While it may be 'normal' for the Tacoma to fluxuate that much while going up a hill, this overcompensation is by far the worst of any vehicle I've owned or driven. I hate that it overcompensates going up hills and, in my opinion, it shouldn't do it, at least not to the extent that it does.

 

stick shift ftw. My cruise control cant downshift me and hardly ever over compensates.

 

In my experience, this is somewhat unique to Toyotas:


My 2004 Tundra did it.
My 1998 4Runner did it.
My wife's 2007 and 2009 4Runner do it.
The 2011 4Runner we test drove did it.


My wife's 2009 Maxima did NOT do it.
My IS250 did NOT do it. (but its a Lexus so maybe the algorithm is different?)
My Hummer H3 does NOT do it.
NONE of my dad's F150's or F250's do it.
My cousin's 2500HD did NOT do it.


Thinking back, I remember some vehicles that I drove while growing up that did it, but things should have improved by now, and in other newer vehicles I have driven the cruise control has improved.


This is one thing that I do not like about Toyota products. While I owned it, I did find it interesting that my Lexus didn't do this...

 

Rented a PT Cruiser in '05, it was worse. That thing was hyperactive.
'07 Ford Explorer did it.
'95 5.7 Suburban did it.
'93 4.3 S-10 Blazer did it.

 

guess i never really noticed it in my parents automatic cars cause i didnt drive them enough or it didnt happen. just thought it was excessive in this situation. oh well, not a big deal

i've pretty much already come to terms with it, just wanted to make sure it wasnt defective

 

I've got a V6 prerunner auto and yeah, the CC is fine on flat land, though the handoff from pedal to CC is slow. But going up a hill....I can hold the gear with manual pedal, but in CC, it will drop down a gear. Really weird.

 

Just found this thread searching for a similar issue. 2x4 2.4 Access Cab automatic.

The problem is my truck never did this until recently. It would maybe go 1 or 2 over after downshifting to catch my set speed, but now it's going 5-7 mph past, before settling back down to my set speed.

Noticed it on a recent trip through some steep hills, figured it was just more noticeable and more prolific with the 4cyl and the hills. But when I got home I realized it was doing it in daily traffic as well. Mostly after hitting the resume switch after breaking and passing traffic.

Disappointed to hear this is expected behavior.