Engine Surge

[BEATZZ]

Maybe i've overlooked this, but can anyone tell me what this might be? After the car has shifted into 5th gear, when I hit the gas, it jerks maybe twice & goes on about it's business, no leaks at the VCG's, no codes, COP's good, what boggles me is that all the gears are strong, but it's right after I gas it around 70mph while in 5th gear.

05 LS just hit 70K miles

 

[97stscaddy]

It's the Torque Converter Clutch disengaging.
Just about every modern car with an automatic transmission is equipped with a TCC. Its a pretty simple system. It uses a small clutch band inside the torque converter and an electro-magnetic solenoid. When the car hits a certain speed the ECM activates the solenoid which then locks down the clutch band inside the torque converter, which mechanically locks the flywheel on the engine to the input shaft of the transmission. The main purpose is to save fuel because when the converter is locked the engine speed will drop about 300 - 500 rpm.

When you hit the gas the clutch will unlock, which in turn raises engine speed closer to its optimum power band. In turn more torque gets to the wheels and you accelerate faster, while using less throttle.

 

[BEATZZ]

Thanks for the reply, I was confused because everyone was talking about COP's & all that & it kinda threw me off, do you know if this is common in these 05's, & what do you think the cost is? Also, how long do you think this can go on before it's repaired?

 

[97stscaddy]

There's nothing wrong with it. Its supposed to work that way. Sometimes you will feel it disengage depending on the speed you are moving or how hard you hit the gas. It will feel similar to the transmission down shifting. As the car gets older, it loosens up, and the suspension and drive train components of the car will develop a little "wiggle room". That doesn't mean there's anything wrong with the car, its just aging. As it does this you will tend to notice movements or wiggles that you couldn't feel as easily before.

 

[LincolnLSE]

The same thing happened to me a few times. I would be cruising on the freeway at 65 or so and then step on the gas a bit. The car would surge slightly and then the RPMs would drop suddenly for just a second and jump back up to where they should be. In any event, it felt very harsh on the drivetrain. This happened about 6 times in a 2 month period, then stopped for about another 2 months. Then at 86,000 I began having symptoms of bad ignition coils - misfires when applying light acceleration between 45 and 60 mph and at idle, decreased gas mileage, burning oil smell through the vents, etc.

Just had all 8 coils and plugs changed as well as both valve cover gaskets (leaking oil into the coil wells, shorting them out causing the misfires). Cost - $1400 parts and labor at a local shop. The dealer quoted me $2300.

Hopefully your problem isn't an early symptom of going coils. Good luck!