Hi. My car has been acting-up sense I had a problem with the battery. It leaked acid on the positive side, so I changed it. A couple of times I had to jump the battery start the car with the old battery. During this time and after I got the new one the car hesitates, doesn't have the same power it used to and it runs rough. I've changed the air filter, the fuel filter, the engine oil. I've checked the alternator, it'* working fine. A mechanic and I scanned it for codes and it doesn't show any of them; but he did notice the car is slow, that it hesitates on cold starts and up hill. The only thing that seems to help is if I unplug the MAF sensor, the car gets its power back and runs smoothly. Does this mean the sensor is bad even thou it'* not giving out a code? Could it be the main computer? What else could be wrong?
Please help! :(
Your suggestions are appreciated

i had the same problems and my cables weren't tightened to the battery tight enough, or it wasnt getting a good ground. Try checking all your battery connections, i.e to the starter, to the alternator, to the fender wall and etc. that was my problem for a while and just tightening the battery cables seemed to fix it. Is your SES light on?

after checking and cleaning all the connctions try leaving the battery unhooked
for at least 30 min to reset the PCM so it may relearn with the new battery.
This may very well be the problem if all you did was change the battery.
I assume it is the correct size and cranking amps as the old one.

I've checked the ground terminals and the terminals to the battery ant htey are ok. Also I've done the 30 min battery unplug rutine but it just seems to make the problem worst.

The Check Engine light is not on. I have already hook-up a scanner to the car but it doesn't show any codes suggesting something is wrong.

Its best to use the process of elimination in this case.
Fuel and poor spark would be my first guess.
Could you have a bad tank of fuel? Bad coil? Spark plug wire? etc etc.
Just keep going down the list and checking. If you scanned it I would think you
would have picked up a missing cylinder.

Running with a faulty electrical system (either battery or alternator) can foul plugs with low spark voltage. Inspect your plugs, and while you're at it, check your plug wires and coils for proper resistance.

Remember that a bad battery can stress and eventually destroy an alternator.

95% of the problems we have here as you describe your symptoms are ignition related in some form or other.