Would it be called surging?
 

I've read through a lot of threads here that talk about surging, but I don't know if I'm experiencing the same symptom. If I set the cruise at 30 or 31 MPH the tachometer jumps back and forth about 200 rpm; enough to feel it. Same thing when setting the cruise at 39 to 41 MPH. Now, to throw the monkey wrench into the diagnosis- this surging will sometime occur just when I am driving at these speeds, and occasionally at around 50 MPH. It happens on level, smooth road. It feels like the transmission is shifting back and forth between gears. After a few seconds of this 'surging' it settles down into a level speed and RPM. The problem started only recently, and I have not yet taken it to the dealer (under warranty). Just wondering if anyone else had this happen to them. Thanks in advance. Bret

I'm having similar issues on my Lumina... Could really be anything from plugs/wires to the transmission. Now, I doubt it's the transmission, but my point is that it could be a huge range of things.

Just be glad you're under warranty!!!!

Some of the threads here that you may find searching the word "surging" have to do with the SS and wouldn't be applicable unless that's what you have. Seems there was one recently that was a transmission problem and was repaired/replaced under warranty.

https://www.chevyhhr.net/forums/problems-service-repairs-42/engine-surging-problem-31305/

As carkid said it could be lots of things.... could even be a bad tank of gas.



:skull:

It sounds like you're feeling the torque converter locking and unlocking as the vehicle tries to maintain a constant speed. While the cruise will work at the speeds you indicated, its really designed for highway speeds which probably damp the surging that you feel. Just curious as to why you use the cruise at such moderate speeds, traffic conditions?

Not to sound like a butt, but why are you setting the cruise at such a low speed? The transmission(auto I assume) most likely is at the in-between point of gear changes.Over the years I have never set the cruise control unless I'm in high gear. You could have other problems but setting the cruise at low speed---wouldn't recommend it.

Not to start a cruse control dispute, but mine works fine at lower speeds, so I wouldn't think what the OP is seeing is because of his use of cruse...... If it was something it wasn't designed to do they wouldn't have made it available. Mine can be set at anything above 25 mph and it works there without issue..... I've tried it.

Is the only place you drive on the highway? There are plenty of roads around here with no stoplights or stopsigns where the speed limit is anywhere from 35 or 40mph. Why wouldn't you set the cruise if you're going a constant speed? It's not only meant for the expressway.... :roll:

I don't see what it would hurt...if it did, they wouldn't let you set it.

And just because the torque converter locks up when it shouldn't doesn't mean it's an issue with that. It could be something which tells the torque converter to work having an issue. Something that communicates with the TCC could be giving it false information.

I often set the cruise at relatively low speeds, 35 to 50MPH, when its appropreate. I have never had a surging problem, though mine is a five speed, which shouldn't make any difference.

Just discussing the issue.Not arguing.I was refering to the OP setting the cruise as low as 30mph thus the in-between gears comment.
I drive on all types of roads.Only use the cruise on the interstate.You must not have the traffic we do.No constant speeds here.Always someone in front slowing down,turning etc.
In reference to "they wouldn't let you set it". I have a 5 speed in this SS and can shift into 5th at 20mph if I wanted.It won't run right.Will bog down. Most likely stall. But "they" let me do it.Think about it.Just because you can doesn't mean you should.
Not saying you are wrong.Just my opinion.:my2cents: