Hi, my 1991 Mercury Sable is running pretty good except that going up hill it feels like it’s in 2nd or 3rd gear instead of drive. Wondering what might be causing this, hope it’s not something expensive.
Based on the information you have provided, I would say it’s in 2nd or 3rd gear instead of drive. That can be caused by a failing transmission, a failing transmission controller, or a failing operator who sticks it in D3 or D2.
Tell us more about the problem (like why you think it feels like that) and we’ll get more specific 
…or, the engine is in need of maintenance.
Beginner’s Luck:
When were the spark plugs, plug wires, air filter and fuel filter last replaced?
There’s not enough info known about the car (mileage, engine type, history, etc) to make much of a guess. To throw some wild guesses out there:
If it’s a 3.0 engine any history of ignition module changes could mean the timing is running retarded if this procedure was not done correctly.
Seriously clogged air filter.
Slipping transmission although it would help to know if it’s really downshifting or not.
RPMs climbing way up?
Clogged converter. This could be checked with a vacuum gauge. A gutless engine may cause the transmission to downshift.
There’s others but that’s a start.
Thanks for the ideas. I had it looked at and the problem was the vaccuum hose. They replaced it and topped off some fluids, for $94.00 and change (I’m in the Northeast).
I called AutoZone and they said vaccuum hose for this car tops out at a little over $2.00 a foot, so not sure this repair was such a great deal - don’t know how difficult it is to replace a vaccuum hose?
Going by parts cost - especially on something as simple as vacuum hose is a terrible way to judge how much you should pay. The least of the problem is replacing the part. The real problem is knowing how to figure out the problem and address it. Don’t short change the value of the expertise required to figure out where to put the $2 worth of hose.
Is the car running well now? If so, then it was $94 well spent.
You won! Finding the defective hose probably took the time and this is where most of the $94 went. In today’s market, $94 is cheap for a repair. Thirty years ago, Sears used to have a bench charge of $20 just to take the back off the cabinet of a television set.
A friend of mine just got back from a 1000 mile round trip. On the way to his destination, his car was having a horrible time climbing hills. He went up one hill in the breakdown lane with his flashers on. It turned out his catalytic converter was plugged (the GoodYear store said collapsed). He had a $900 repair bill just to get home. At $94 consider yourself lucky.
you have to take into account the lease on the garage, the power bill, the time and training the mechanic went through to know what to do, and the time to do the job, not to mention the cost of lava soap to get at least some of that grease and grime you hate off of his hands.