Check engine light on. I changed the sparks plugs, changed oil & oil filters, changed air filter and pour a STP complete fuel injector cleaner (gray bottle) and the light still on. Had Auto Zone checked and they found a troubleshooting P0303 - cylinder misfire detected-cylinder #3. What can I do??

its either the fuel, spark plugs, or not enough air to complete the combustion cycle. Check the air filter to ascertain its not dirty. Check spark plug connections to ascertain there's a current from distributor cap to spark plugs when the starter motor turns. Spray starting fluid for half second before turning engine, and don't give throttle until engine starts, then increase throttle to 2,000 RPM. Once a month, pour a bottle of fuel injector cleaner to keep the injectors clear of debris buildup on the injectors' tips.

replace all spark plug wires. check plugs , pull a few out, note condition, I would replace them also. inspect distributor cap/rotor, I would replace them also. see how that works for you, a new air & fuel filter is always a plus, if you depend on your car, it depends on you too ! today gasoline has 10% ethanol, its garbage for older cars, add some fuel injector cleaner to tank, and change oil & filter, DO ALL THIS TO SAVE YOUR CAR ! just do it !!!!!!!!!!!

• Plugs - every two years for the single fire plugs up to 90,000 miles for the split fires etc.
• Wires - every two years on up depending on quality of wires.
• fuel filter - every 15,000 miles or so.
• air filter - as needed but every 10,000 miles or so.
• antifreeze flush - 30,000 miles for green, 75,000 for organic (Dex-Cool style)
• transmission fluid flush - every 40,000 miles.
• transmission gasket and filter change - every 100,000 miles.
• timing belt - every 100,000 miles.
• Rotate the tires every 6,000 miles or so.

Regards, Tony

first check the codes, from the check engine light, could be a spark plug , coil , wire, or eng. probs.

- Spark Plugs (make sure they are gaped properly)
- Spark Plug Wires
- Coil Packs (if needed) or Distributor Cap & Rotor (which ever so equipped)
- Air Filter
- Fuel Filter
- Oil
- Oil Filter
- Transmission Filter (optional)
- Transmission Fluid (optional if you do change the trans filter you will need the fluid)
- PCV Valve (optional)
- Bottle Of Fuel Injector Cleaner (add to fuel tank kind)

Tune Time.
1)new spark plugs properly gapped.
2)new air filter (check every 35000 miles)
3)new fuel filter (every 35000 miles)
4)1 bottle of STP fuel treatment (red bottle) 4x a year.
5) oil and filter change (castrol or another good quality oil every 3-4000 miles.
6)proper air pressure in tires (check every 2 months
7) service transmission every 40000 miles or less.

New oil and filter
8) new plug wires every 80000 miles.

SOUND LIKE DIRTY FUEL INJECTORS.FILL GAS TANK UP.POUR A BOTTLE INJECTOR CLEANER IN GAS TANK.DRIVE CAR AROUND.SO THE CLEANER CAN CLEAN OUT INJECTORS.ALSO REPLACE FUEL FILTER.HEY YOU CAN GO TO AUTO ZONE OR ADVANCE AUTO THEY WILL SCAN YOUR CAR FOR FREE.

New fuel filter, Spark Plugs & Wires, New air filter.
Tires at max cold psi.
Use a bottle of injector cleaner and change oil every 3k

Sounds like a fuel/air problem. Replace fuel filter, check/replace air filter and spark plugs, complete the tuneup and see what happens. If it still happens then suspect injectors. Run cleaner through a tank of gas. If still the same take it to a shop that can plug into your vehicle and verify injectors performance.

check the fuel filter first to see if it is plugged pour some STP gas treatment with injector cleaner into the gas tank and also check the injectors if this helps then you will need to change the fuel filter