Misfire of the #3 cylinder, 4.3 6 cyl

Believe it or not the firing order is 1-2-3-4-5-6 The cylinder locations are 2-4-6 in front by radiator, and 1-3-5 against the firewall. If you have a misfire on a certain cyl. and you've replaced the plugs,wires and cap and rotor, you probably have a fuel injector that's dead or plugged,it's common on Quests. Figure out which cyl. is misfiring and unplug the fuel inj. conn. with the engine running and listen for a change in RPMs. If there is no change then replace the injector.

check spark plug of the cyl. switch plug with another cyl, run engine until warm to see if misfire still comes on. if it stays on the same cyl. fault could be high tension wire or coil or worse leaky valve or rings. if misfire switched to the other cyl just change plug or better replace all plugs

this code identifies that the computer in your vehicle has picked up that cylinder 3 is not fireing properly so i would say change the plug in cylinder 3 if not cured change the plug lead if thes dosent work then distributer cap or the electronic distributer check all these things in this order its just elimination really

I have 2002 Accord se I have engine light on, cod is po303 cly 3 misfire and po1399 ignition manuf- may misfire, I replaced new plugs, wires, distributor and cap, o2 sensor,head gasket, an Light still cam on. can any one help.

Spark plugs,wires and injectors, have nothing to do with your problem

PO303 is a misfire on cylinder #3
You may have an individual cylinder coil for that cyl or a coil pack for
several cyl,don't know the engine you have.

You may also have other issues that are causing the shaking

could be fuel injectors flooding cilinder fuelregulator not working right there is new up gradeinjector system

the code that is given means that the coil, plug ,plug wires, for that cylinder could be bad, check spark plug and see if this is the problem or a bad wire.

Check vacuum lines going to evap canister for cracks or splits, causes to much raw air intake.

might be the coil pack is bad, wires, plugs, o2 sensors, dirty injectors, catalic converter ( only if you smell rotten eggs ) . cylinders are misfireing.

cylinder 1 misfire and low compression. Plugs and wires changed plus new fuel injectors. The engines still misses and no one can find the cause. When put on the computer it read misfire cylinder 1.