Although the torque converter clutch is not part of the engine, it can make the car feel like the engine has a problem. The torque converter clutch is also known as a lock-up converter. The lockup clutch has many purposes and is part of the transmission. A regular converter in an automatic transmission is made to slip at idle so the car doesn’t move. As the throttle is pressed the RPMs increase and the torque converter will start to lock up or kick in. When the converter is activated, the car will move.
Even though the torque converter is engaged, it never fully engages the way a manual transmission car’s clutch will. It will always slide a bit, which is not very efficient. This is why a manual transmission car gets better fuel economy and has more power than an automatic transmission car. To increase power and primarily fuel consumption, a TCC is added to an automatic transmission.
The torque converter clutch is an electronic clutch that will engage the engine and transmission at 100 percent. The TCC is made to generally only engage in top gear when the car is cruising, not accelerating. The lockup converter will disengage when the throttle is pressed hard enough. Over time, the clutch will wear out, especially if the vehicle has ever towed anything and was operated in overdrive (top speed). This will wear out the clutch prematurely. If you have a tachometer you will see the RPM drop a few hundred when it is activated.
If the TCC is bad, one of three things will usually happen. First, the vehicle will tend to rev up and down as it engages and disengages, and will not be able to keep the converter clutch engaged. Second, the converter clutch will randomly engage in gears where it normally shouldn’t even engage. Third, the clutch doesn’t want to let go. As you slow down, the vehicle will not downshift and if you try to accelerate, the RPM will be so low that the vehicle will have difficulty moving quickly. In extreme cases, the lockup converter will try to keep the vehicle moving while trying to stop at a traffic light, or it will stop and die.
Many people think that this problem comes from their engine because it causes the car to stall. The check engine light will not always show an error for the TCC. Most lockup converters are controlled by a cable or cables that connect to the transmission. On some models it is possible to simply unplug this plug. This is not a problem and will only cause you to lose a little gas mileage. The RPM will run a bit higher than before, but won’t hurt anything or be a problem.