Using cruise control is no different than holding a speed with your foot, it's just the computer controlling the throttle. Some type of programming change might be necessary for better teamwork between the engine and transmission.

 

I have the same problem with my '06. Under normal acceleration, it seems to shift from 3rd to 4th too soon and then the rpms start to fluctuate and will continue until it shifts into OD. The throttle body has been cleaned, but it still surges. I'm thinking it might be the transmission. Is there a software update for the trans?

 

Thanks for all the ideas.

I should have mentioned that this problem started only recently, after having owned the vehicle for 1 year.

I use the cruise to avoid having a heavy foot. It's a great way to not get speeding tickets. My drive to and from work is 35 miles each way, and good portions of it are on level roads, so the cruise is a great tool to avoid foot and leg cramps. Besides, you set the cruise then can 'feel free to move about the cabin'.

 

"It's a great way to not get speeding tickets."


Same here.


I was serious about it being a bad tank of gas, any possibility of that?

 

There are plenty of sensor that could be throwing things off too... I just replaced the Vehicle Speed Sensor on my Lumina...going to see if that helps.

 

Hey, Grey. I'll be filling the tank tomorrow, and adding injector cleaner at that time. I also have a new air filter that will go in once I have the time. It's off to the dealer if that don't fix it.

I also have the cabin air filter, but I somehow think that might not affect the engine symptom.

 

Make sure the fuses and relays are seated well in the fuse box under the hood. I recently bought a 2006 and it did this, on occasion. After reseating all the fuses and relays it has not happend since.
This may or may not fix your problem but it worked for me.

 

Checking the relays is a good thought. I travel about 7 miles a day on a very rough gravel road.

 

So, I finally had time to get this to the dealer. (I have 38K miles, but purchased a service contract.) The service manager said it's a dirty throttle body. I will attempt to clean it this weekend (weather permitting.) It is a "maintenance issue", so is not covered under GM's service contract.
Neither are the badly scored rotors.
Nor the very rich (unburned fuel) exhaust smell.

 

I set the cruise at 30 on one road only. It has a low speed limit and often has speed traps.