QUESTION -- I am having problems with no passing power on my 1994 Mercury Sable. It has a 3.8 L engine and high mileage. The car has pickup at the start, but in second gear when you accelerate, the car's r.p.m. ramp up to 4,000 r.p.m. with no pickup. Then it slowly accelerates. If you don't push it, the car will shift through the gears and slowly accelerate.
I have replaced spark plugs, wires, fuel filter, purge valve and hose because there was a break in the hose. There is a noise from the muffler and it will need replacing. Could the lack of passing acceleration be caused by a partially plugged catalytic converter or would it have something to do with one of the oxygen sensors? On a '94 car, can one dispense with the catalytic converter completely? Your thoughts on this matter would be appreciated.
A 1994 Sable was the Mercury version of the Ford Taurus.
ANSWER -- I think you are looking in the wrong area. If the engine is able to rev to 4,000 r.p.m. during acceleration with no increase in vehicle speed, the problem is in the transmission rather than with the engine. During the shift from first gear to second gear, the computer applies the intermediate clutch pack. It does this by turning on a solenoid, which controls the flow of hydraulic pressure inside the transmission valve body of the AXOD-E transaxle.
The change in flow inside the valve body moves a shift valve, which in turn directs transmission oil to apply the intermediate clutch. When the clutch applies, the overrunning clutch (a one-way mechanical clutch) that drives in first gear begins to overrun or freewheel, allowing a smooth shift to second gear.
Two problems could result in your car's symptoms. First, the shift valve in the valve body may be sticking, allowing only partial application of the intermediate clutch. These transaxles are very sensitive to assembly techniques and even removing and installing the valve body can cause valves to start sticking. Even torque is critical. In your situation, however, the shift valve may have become varnished and isn't moving completely.
The second cause could be a bad seal or worn clutches in the intermediate clutch pack. This is allowing the clutch to slip. Both causes will result in the clutch to slip, generating excessive heat and burning the clutch material. You will need to have the transaxle overhauled to fix this problem.
As for removing the catalytic converter, it is possible, however I wouldn't recommend it. As long as the catalytic converter is not plugged, it is not reducing engine power. However, if you do remove it, exhaust backpressure will be reduced slightly and this will cause codes to set for the Exhaust Gas Recirculation (EGR) system. These codes will cause the computer to modify engine operation and this could result in reduced power and the check engine light coming on.
QUESTION -- Hopefully you may assist me in a problem that we have with our 1999 Olds Intrigue and the air conditioning. During the summer, the outside temperature reading does not properly work. When it is well above zero, the reading may start at about 8 C and then slowly drop to about 0 or -1, where it will stay. At this reading, the air conditioner cuts out. I assume this feature shuts down the air conditioning to prevent damage when the temperature actually is below zero. In reality, the outside temperature may be 25 C, which makes for a pretty warm interior when the air conditioner cuts out.
I replaced the ambient temperature sensor located just behind the radiator but that did not seem to solve the problem. Any assistance would be appreciated.
ANSWER -- You are correct in assuming the compressor cuts out when outside temperature readings are low. Usually this occurs about 4 C. Your problem is that the actual temperature is warm but the sensor is indicating cold. High resistance on the sensor circuit will cause this. Check the terminal connections at the temperature sensor. There is also an in-line electrical connector (C120) on the right fender near the battery. You are looking for the light green wire with a black stripe wire. Finally, check the connections at the 32-way plug at the rear of the air conditioning control head. You could measure the resistance of the sensor wiring with the control head disconnected. It should measure very close to the same as the actual sensor. Although the problem could be internal in the control head, I suspect you will find a bad wiring connection is the cause of the problem.
Jim Kerr is an experienced mechanic, instructor of automotive technology and member of the Automobile Journalists' Association of Canada. You can e-mail questions to Jim at the address below.
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