torque converter lockup
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 lockup converter. The lockup clutch serves many purposes and is part of the transmission. A regular converter on an automatic transmission is made to slip at idle so the car doesn’t move. As the accelerator is depressed, the RPM increases and the torque converter will begin to lock up or engage. 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 slip a bit, which is not very efficient. This is why a manual transmission car gets better gas mileage and has more power than an automatic transmission car. To increase power and mainly 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. TCC is made to generally only engage in top gear when the car is cruising, not accelerating. The lockup converter will disengage when the accelerator is pressed hard enough. Over time, the clutch will wear out, especially if the vehicle has ever been towed and operated in overdrive (top speed). This will wear the clutch prematurely. If you have a tach you will see the RPM drop a few hundred when it kicks in.
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 locked up. Second, the converter clutch will randomly engage in gears that 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 a hard time moving quickly. In extreme cases, the stall converter will try to keep the vehicle moving while trying to stop at a traffic light, or it will stall and die.
Many people think that this problem comes from your 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 disconnect this plug. This is not a problem and will only cause you to lose a little gas mileage. The RPM will run a little higher than before, but it won’t damage anything or be a problem.