2002 Jeep Liberty with engine light on. I can't get it off. Help?

[KELLEYD]

I took my Jeep to an auto parts store and they said O2 sensor was bad.  I replaced it.  Light came back on.  I was told emissions, so I took it to a mechanic.  He said cylinder 1 was misfiring intermititeIy and suggested replacing the gas cap first.  I replaced the gas cap and two pressure hoses that could have been the problem.  I added fuel treatment to clean up the engine.  Light is still on.  Mechanic suggested a tune up.  That's spark plugs and plug wires right?  I need a little guidance.  Where do I start?  If that doesn't remedy the problem, what's next?  Can you replace a cyclinder?  If so, what's the cost?

[Dan]

it would be alot cheaper to let a pro fix it then spend money replacing parts you don't need like you have already done. just because a code sets for a o2 sensor doesn't mean the sensor is bad, you have to go thru a flow chart and determine the problem. that is why mechanics get paid to diagnosis problems. auto parts stores sell parts and can read a code not diagnosis it

[RobinB]

You will need to have the computer reset. This happens on this model. Make sure you have checked all the recalls too. Mine did  this, it turns out it was a recall thing, and they had to reset the "brain", so that it no longer registers a problem. This should have been done where you had it worked on. Frankly, I take my liberty to the jeep dealer only, as they have the up to date sensors and equipment for this. You could have a diagnostic exam done on it at a dealer, to see the why this is happening.

Go to Jeep.com and check out the recalls

[fireprotek]

if #1 cylinder misfires, try to switch another spark cable with #1 spark cable and see if the problem is the spark cable or the distributor .

[sprinkles]

a gas cap or cracked evap hose will not cause a misfire.  you most likely need a tune up.  spark plugs only-it does not have wires.  it could also be a coil, injector, or valvetrain problem but spark plugs have to come first.