Code 303 Cylinder 3 Misfire? - Forums at Modded Mustangs
 
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post #1 of 8 Old May 14th, 2010, 01:27 PM Thread Starter
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Code 303 Cylinder 3 Misfire?

So I was driving my car today and it started to run like crap. The SES light came on and it threw Code 303 Cylinder 3 misfire? What would cause this? I just replaced the plugs about a week ago! Thanks!

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post #2 of 8 Old May 14th, 2010, 01:44 PM Thread Starter
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I'm guessing a bad COP? Do these go bad often?

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post #3 of 8 Old May 14th, 2010, 01:45 PM
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It's not real common for them to go bad, but it might have. Do you have a friend that could pop one off thier car and see if it fixes it?

If the COP and injectors are ok, the problem almost has to be internal

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post #4 of 8 Old May 14th, 2010, 03:29 PM Thread Starter
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Quote:
It's not real common for them to go bad, but it might have. Do you have a friend that could pop one off thier car and see if it fixes it?
I replaced the COP and it's still throwing the code. I guess that leaves me with either a bad injector or internal motor damage? BTW the car has 70K......

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post #5 of 8 Old May 14th, 2010, 08:10 PM
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i had a similar code before when i got my 4v swap done on my GT. turns out a vaccum leak played a big part in it. check your vaccum lines 1st. another trick is to replace the #3cyl COP with another COP from a diff. cylinder and see if the miss follows the change. if it isnt the COP or the plug, then like you said its probably the injector.



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post #6 of 8 Old June 21st, 2010, 01:54 PM
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I have cylinders 1, 2, and 3 missfiring, what should i check first?
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post #7 of 8 Old June 21st, 2010, 04:13 PM
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do you have fuel?

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post #8 of 8 Old June 21st, 2010, 04:16 PM
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yes
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