Oldsmobile/Buick Repair: car trouble blues, oldsmobile alero, 2002 oldsmobile alero

Question
I have a 2002 oldsmobile alero, 4 cyl. and recently had brake linings put on my vehicle. i drove the vehicle appr. 27 miles home and it ran fine. the next morning i went out and started my car the ETS or trac off light and service engine light soon came on and stayed on steady. i also noticed that engine power was cutoff. i took it to a garage and they hooked it up to an obd computer system and it said misfiring. they changed the plugs but the problem still didnt fix, and they said they didnt know what it could be. I also recently put fuel in the vehicle and wondered about the gas quality? Any helpfucl ideas would be great. thanx

Answer
Hi
It may be the fuel
I would take it to a DIFFERENT shop and have a better mechanic look at it. I am suprised "they didnt know what it could be". You need another mechanic.....
It COULD be a fuel injector clogged or dirty.
This could be diagnosed by preforming a fule pressure drop test.
I would advice a different shop, have them repair it.
I Hope this helps
Pawl