Engine code p0300, p0303,p0304

[tang02]

I was driving my 2002 mustang gt convertible to my brothers house last evening and my engine started having a bad miss at high rpms. pulled these codes with my predator.... p0300 p0303, p0304.

It missed real bad then seemed to clear up. I had just bought a tank of gas at a small gas station here in ky, shell wasnt close by. I usually get theres and 93 octane.

The problem seemed to start after I bought the gas.

So I ran the tank to half empty and went to shell on my way home and bought some 93 and put a bottle of 103 octane boost in the tank. It seemed to get better the more i drove it. The stumbling and miss dissappeared but it still trips the p0303 code.

Do you think it was the gas or is it something that will get worse?

My mustang has 36k on it. So its pretty much low miles. I put new ngk plugs in it last year and it has a bbk cold air, throttle body and plenum.


Any insight is much appreciated

 

[liltiffey]

I have a similar problem mine is only popping up p0303... i dont know what i should do. i changed all plugs and checked the wires. i thought i fixed it but its still jerky... i got gas the night before and but lucas in the gas tank nothing as changed. have you found out what is wrong with yours?

 

[wmburns]

When resurrecting and piggy backing on a 5 year old thread, it might be handy to include some important details. Like the model year and engine of your car.

If this is a COP car, try swapping the COP to another cylinder.

If this is a coil pack car, try inspecting the spark plug wires for white spots. Or if the wires are old, change them.

Consider swapping the #3 injector to another cylinder. Or better yet, consider an injector cleaning/flow test service such as Injectorrx.com.

 

[apats77]

well the codes are p0300 multiple misfires detected p0303 misfire in cylinder 3 p0304 mis in cyl 4.