I've noticed a 3-5 mile per gallon drop in fuel economy in my 98 3.0l Caravan recently. Is there any way to test if the torque converter lock-up is functioning correctly?

 

Its a 3 speed or 4 speed trans?

Listen carefully to the engine rpms will driving 45-50 mph. if you very lightly tap the brake pedal the converter will unlock and the engine rpms will go up slightly. This is real easy to see if you have a tachometer.

good luck

 

I think it's a 3-speed. I've been noticing a weird feel to the drive train. It doesn't seem to "freewheel" when you let off the gas like my other 98 Caravan did.

There has also been some very very slight, almost imperceptible "hesitations" that will happen intermittently over the course of a day...only one at a time. I'm not sure if those are related to the transmission, but they seems to coincide with the drop in fuel economy.

Unfortunately I have no tachometer, but I will give that brake pedal trick a try.

 

Do you have a check engine light on? Because if you have lock up torque converter problem, that would have given you a code for the lock up solenoid.

 

If you live in an area with cold weather, the mileage will drop some but not as much as you've mentioned. Any chance the brakes are dragging?

 

A light came on after I had some service done (the work was done on the engine AND transmission around the same time). I had assumed that was caused by a vacuum line I noticed the mechanic had left off on the intake. I reconnected the vacuum line and disconnected the battery....so I'm not sure it could have been the transmission that reported the error code.

 

This is a much bigger drop than last winter. I did notice the thermostat was bad, because the engine would operate very cold, thus in theory making the mixture fuel-rich. I had the thermostat replaced and now the engine is running at normal temps...incredibly the fuel economy DROPPED another 1 mpg after the thermostat replacement!!! There has to be a drag somewhere. I don't think it is the brakes. I just had all tires replaced and the shop didn't mention anything.

 

Update: this thing is definitely shifting into 4th gear...it has to be a 4-speed. I don't feel the lock-up in any gear as I did with my other 3 caravans. I did the brake tap test and did not perceive any difference in RPM's. I did have the transmission flushed recently, around the time the trouble started. Actually, they had to re-do the flush because on the first one they used a paper gasket that leaked. They replace it with a cork gasket and re-filled. I usually confirm that they are filling the trans with ATF-4 but did not this time around. Hope he didn't mistakingly put Dextron in. Could the wrong fluid cause the lock-up not to function?

 

If they used something other than ATF4 you would experience a lot more than just lock up issues. A lot of junky shifting and such.

Regards
Issakar