Maxima97GLE

When I start the car it idles fine... when i through it into "D" or "R" it stalls out or vibrates. When I finally get the car rolling I'll accelerate very slow with the RPM's revving at 1300... Can anyone else besides "Baldie" tell me if this has ever happend to them and what it was or how to fix it?

Daniel B. Martin

A thorough diagnosis of a misbehaving automatic transmission involves a road test, a Stall Test, and a Line Pressure Test. Most owners, even home mechanics, don't have the equipment to perform the Line Pressure Test. However, we can do some useful diagnostic work with the Stall Test. The results of a Stall Test can implicate the torque converter or the automatic transmission.

One of the classic symptoms of a bad torque converter is a vehicle that is sluggish or lugs when starting out from a dead stop. The vehicle may feel as if it is in second or third gear rather than first gear. What’s happening is the torque converter is failing to provide any torque multiplication because the one-way stator clutch is not holding, allowing the stator wheel to slip.

To test the torque converter, you need to perform a stall test. This will reveal the maximum engine rpm the converter can handle without the vehicle moving.

Check the engine fluids and Automatic Transmission Fluid. Add fluids as required. Road test the vehicle, driving it for at least ten minutes. During the road test, make notes of
- acceleration from rest
- engine braking (or lack of same) in each forward gear.

Apply the hand brake. Block the wheels with suitable chocks. Start the engine and allow it to reach normal operating temperature.

Shift the transmission to "D". Press the brake pedal firmly with your left foot and press the accelerator pedal with your right foot to increase engine speed until engine rpm will go no higher. Note this rpm, it is called the "stall speed". Release the accelerator pedal and allow the engine to return to idle. Shift the transmission to "N" and allow the engine to idle for two minutes, to cool the ATF.

Repeat the Stall Test with the transmission in position "2", and note the stall speed. Allow another two minute cool-down period.

Repeat the Stall Test with the transmission in position "1", and note the stall speed. Allow another two minute cool-down period.

Repeat the Stall Test with the transmission in position "R", and note the stall speed. Allow another two minute cool-down period. Turn off the engine.

The duration of each Stall Test must not exceed five seconds because the churning of the fluid inside the converter produces a lot of heat.

The stall speed for a healthy 4Gen torque converter is 2,000 to 2,300 rpm.

If the Stall Speed is below 2,000 rpm and a road test confirms poor acceleration from rest, suspect a seized one-way clutch in the torque converter.

If the Stall Speed is within specifications but a road test confirms the vehicle cannot exceed 50 mph, suspect a seized one-way clutch in the torque converter.

If the Stall Speed is too high in "R", and the road test indicated
- a lack of engine braking in the "1" position, suspect Reverse clutch slippage.
- normal engine braking in the "1" position, suspect Low & Reverse brake slippage.

If the Stall Speed is too high in "D", "2", or "1" positions, and
- slippage occurs in 1st gear but not 2nd and third gears, suspect Low one-way clutch slippage.
- slippage occurs in 1st through 3rd gears, and engine braking was normal, suspect forward clutch or forward one-way clutch slipping.

gtr_rider

iTrader: (50)

damn your god.