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Car is jerking when going up hills and accelerating?

So when I am driving along and the vehicle is in top gear and I begin to go up a hill and the car needs to downshift to maintain the speed it begins to jerk around like it is having trouble downshifting. Also sometimes when sitting at a red light or stop sign the vehicle jerks a little. It will sometimes also have trouble taking off from a stop when I accelerate quickly; it is again a little jerky. I took it to the shop and they said there are no ?codes? on the transmission and they could not replicate the jerking when they took it out. It is a 2002 mercury sable LS with about 82000 miles on it. Anybody have any ideas what it may be so I can suggest it to the mechanic?

Automatic or manual transmission?

Have the spark plugs been replaced? Do you know if the mileage may have gone down?

I just bought the vehicle so I am not sure if the spark plugs have been changed or if there has been a change in mileage. It is an automatic.

I think I’m first thinking along the same lines as Mr. Meehan - my first guess would be misfiring rather than a transmission problem. And I’d start with a new set of plugs and wires, a check of the air filter, and a new fuel filter.

I did just replace the air filter last week. I am taking it in to the dealership tomorrow and will let them know what you suggested.

Thanks

Do you really want to go to the dealership for some reason? Any reputable, local, independent mechanic can work on this car - and probably for a lot less $$.

The dealership will be doing the work for free. Like I said I just purchased the vehicle two weeks ago, so they are willing to work out any issues I may have.

ahhh…that makes sense. Make sure that you keep a good paper trail - I’d even take notes on conversations. If things drag out long enough you’ll eventually find “their problem” blending into “your problem.”

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Spark plugs perhaps, or it could be the fuel pump going bad.

things to have them do:
all fluid changed(oil, transmission, etc), spark plugs and wires, air and fuel filter, and anything else mentioned in the owner’s manual for the miles on the car.

I’d bet that a set of spark plugs, spark plug wires, and a new cap & rotor will cure this jerking. Rocketman

Change the FUEL FILTER first and see what happens…

Do you mind telling me what you paid for the car. I ask because I have a 2002 Ford Taurus with 75000 miles on it and I am thinking about selling it.

Does the 2002 Sable really have a distributor? That seems very unlikely.

Good point . . . can’t see it from here . . . but whatever is that equivalent in the '02 Sable in the ignition system to a distributor-point-cap-rotor setup, should be changed. Rocketman

That would probably be COPs (Coil on Plug). Those are expensive to replace without knowing if any are at fault. (usually about $60 x 6 for the parts alone.)

I do agree that there is a good chance that the problem is ignition related. Maybe the dealer will scope the coils.

Turns out it was a misfire under load. They replaced and re spaced the spark plugs and the problem was solved.