Service Engine Light

[White_02_GT]

Hello everyone,

Im new and just purchased a 2002 GT with 93k on saturday. It has a magnaflow exhaust and an aftermarket filter. Other then that it is pretty much stock and the body is in great condition. After driving it around the Service Engine light came up and after scanning the computer it pulled up the following 2 codes P0304 and P0316. In the book its saying missfire can this be a spark plug problem or something else? Im pretty new to engines and really want to learn.
Also if the o2 sensor haven't been change should I change it since it has 93k?

Thank you for your help

 

[Mike96GT]

hey now that you say that , I remember a few guys asking if I ever had spark plug problems. I think the 99-04 may have an issue with that but I could be wrong. I never had any issues but see what other members say if thats common. I would think you would feel it while driving though.

 

[White_02_GT]

How would i know if the spark plugs are bad?

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[mustangsally1]

look at a new spark plug and look at the used one.... im pretty sure common sense will take over from there

 

[DARKHORSE02]

i could be the plugs. at 93k it wouldnt hurt to change them. also the coils do go bad. it could be one of them.

 

[White_02_GT]

What spark plugs do you guys recommend n coils?

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[DARKHORSE02]

do the plugs first. motorcraft. do u know which cylinder is misfiring. dont start throwing expensive parts at it right away. start with the easy stuff that should be done at this mileage. plugs,fuel filter, clean the airfilter , bottle of injector cleaner.

 

[White_02_GT]

Its misfiring at first 1000 rpms n in the 4 th cyclinder. When i change the spark plugs do need to do anything to the new plugs like oil them or something or just put them right in?

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[White_02_GT]

Which ones are better going from motorcraft nickel or platinum?

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[FrostByte]

I had a problem with that error code last year. After much misdiagnosis by the Ford dealer it turned out to be a bad alternator creating radio interference & PCM to give a false code.

 

[White_02_GT]

Yeah ive been reading alot aboit faulty alternators. I figured i will give it a try with the plugs n go from there.. figured i should replace them, o2 sensor, fuel filter @ 93k miles and the previous owner didnt change them

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[MineralGray02K]

I had a problem with that error code last year. After much misdiagnosis by the Ford dealer it turned out to be a bad alternator creating radio interference & PCM to give a false code.

I had the same thing happen with my car, but the code was P0340.

White_02_gt is the code P0304 or P0340?

 

[White_02_GT]

P0304 which is a misfire at the first 1000 rpms n p0316 is a misfire in the 4 th cyclinder

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[White_02_GT]

I honestly did not feel a difference in driving or anything, but this could also be bc ive only had the car since saturday

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[92BIGREDBEAST]

When the guy sold you the car he probably unhooked the battery, wich resets the computer, after you drove it the error code came back. You should make him pay for the parts to fix it. Its a cheap way of hiding a code. Ususally within 100-150 miles after the batter is hooked back up the error codes arise. Call him and see what he says. GL

 

[White_02_GT]

I could do that only problem hes 70 miles away from me, but i will see what he says anyway. I dnt mind spending the money as long as its nothing major i knew buying the car it would need stuff n i pretty much bought the car as a weekend toy n to learn to do stuff to cars.

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[DARKHORSE02]

go with the platinums.if you are getting a tuner they recommend regular copper plugs.

 

[White_02_GT]

I just found out my spark plugs were changed in October n then the car was sitting for sale. I decided to take the car out bc i want to see if i felt a difference n still trying to learn the whole stick thing. As i was driving home i noticed the service engine light was off. I do remember when the light first came on i checked the gas cap which wasnt on well at all.. im still going to check the wiring n make sure everything is on tight.. how do u check if a coil is bad?? Well hopefully it was the gas cap n i can start using my money on some mods now

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[Realspeeddan]

If they are the original spark plugs you should definately change them. (I know you are not the original owner so you may not know if they are original)

If you don't want to have to change the plugs again for at least 50,000 miles you should install motorcraft platnum plugs. If you want to save money now but have to replace the plugs again in 20,000 miles you can get any name brand stock-heat-range replacement copper/nickel plugs, such as Autolite brand. The performance "now" is the same. The difference is that the platnum plugs last much longer.

If you are planning to install a supercharger or nitrous oxide in the next 6 months don't pay extra for platnum plugs now, since will want to change to a different spark plug with the supercharger/nitrous.


A bad alternator can cause misfire codes from electrical interference, but if the plugs are original at 93,000 miles they need to be changed anyway, so do that first.

 

[White_02_GT]

the owner of the car before is mike96gt i have been going back n forth with him he replaced the plugs with ford racing back in October as well as the belt, air filter n fuel filter .. he rlly took care of the car so i think it was the gas cap or possibly alternator. I will see if the light comes back on this weekend.

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