The key to diagnosing torque converter clutch (TCC) shudder is to observe when the symptom happens and under what conditions.

TCC shudder should only occur during the apply or the release of the TCC clutch.

While TCC is Applying or Releasing

If the shudder occurs while TCC is applying, the problem may be within the transaxle or the torque converter.

The clutch is not becoming fully engaged or fully released, or the clutch is trying to apply and release at the same time. This could be caused by any of the following conditions:

Shudder Occurs After TCC has Applied

Most of the time nothing will be wrong with the transaxle. Engine problems may go unnoticed under light throttle and load, but become noticeable after TCC is applied when going up a hill or when accelerating, due to mechanical coupling between the engine and the transaxle.

Important: Once the TCC is applied, no torque converter assistance occurs. Engine or driveline vibrations may be unnoticeable before TCC engagement.

Inspect the following components to avoid misdiagnosis of TCC shudder and possibly disassembling a transaxle or replacing a torque converter unnecessarily:

Spark plugs: Inspect for cracks, high resistance or broken insulation.

Plug wires: Look in each end. If red dust or black carbon is present, the wires are bad. Also look for a white discoloration of the wire indicating arcing during hard acceleration.

Coil: Look for black on the bottom, which indicates arcing while the engine is misfiring.

Fuel injector: The filter may be plugged.

Vacuum leak: The engine will not get the correct amount of fuel. The engine may run rick or lean depending on where the leak is located.

EGR valve: The valve may allow too much unburnable exhaust gas and cause the engine to run lean.

MAP sensor: Like a vacuum leak, the engine will not get the correct amount of fuel for proper engine operation.

Carbon on the intake valves: This restricts proper flow of air/fuel mixture into the cylinders.

Flat cam: The valves do not open enough to let the proper air/fuel mixture into the cylinders.

Oxygen sensor: The engine may run too rich or too lean for too long.

Fuel pressure: The fuel pressure may be too low.

Engine mounts: Vibration of the mounts can be increased by TCC engagement

Axle joints: Inspect for vibration.

TPS: The TCC apply and release depends on the TPS in many engines. If TPS is out of specification, TCC may remain applied during initial engine starting.

Cylinder balance: Bad piston rings or poorly sealing valves can cause low power in a cylinder.

Fuel contamination: This causes poor engine performance.