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Discussion Starter · #1 ·
Just recently bought a 2003 Mustang Gt. Last night I noticed it was running a little rougher than normal. Sure enough, on my way home from work the "service engine soon" light came on. So this morning I took it to Autozone and they ran a diagnostics on it and it said there is a misfire in the 4th and 7th cylinder? I'm pretty worried this is going to be something major/expensive to fix.

Any ideas, or suggestions anyone?:headscratch:
 

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these engines don't like humidity inside the spark plug holes,sounds like it needs 8 new plugs and probably one or two ignition coils.
 

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Discussion Starter · #3 ·
these engines don't like humidity inside the spark plug holes,sounds like it needs 8 new plugs and probably one or two ignition coils.
So a new set of spark plugs and possibly some ignition coils should take car of it? How much do you think that'd cost me?

By the way thanks a lot for responding! Appreciate the help!
 

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a bad O2 sensor will cause a misfire among other things thats why it's important to know what code is thrown, my scanner shows the code and then I have to look it up.
 

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Discussion Starter · #7 ·
a bad O2 sensor will cause a misfire among other things thats why it's important to know what code is thrown, my scanner shows the code and then I have to look it up.
Damn I wish I would have seen it.
I won't be able to have it work on till Monday.

Will driving around make it worse? Or is it ok to drive around for a few days?
 

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You should do this job yourself. Its easy. First I would pull the coil packs and make sure they are clean of moisture. Then pull the plugs and make sure they are in good working shape... replace if needed. Try that before you go run out for coil packs because they can get costly.

And don't drive it.
 

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Just recently bought a 2003 Mustang Gt. Last night I noticed it was running a little rougher than normal. Sure enough, on my way home from work the "service engine soon" light came on. So this morning I took it to Autozone and they ran a diagnostics on it and it said there is a misfire in the 4th and 7th cylinder? I'm pretty worried this is going to be something major/expensive to fix.

Any ideas, or suggestions anyone?:headscratch:
I always tune up a car when I get it, regardless of the history. In your case I would replace all 8 spark plugs, go with the Ford Motorcraft factory ones. Then erase the check engine light. After that see what happens; see if it runs rough and see if the CEL comes back on. These cars are known for bad coils. If the CEL comes back on and you have the same cyl. 4 and 7 misfires. Move the coils to a different cylinder and see if the misfire moves. If it does, you know it's a coil.
 

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Discussion Starter · #11 ·
You should do this job yourself. Its easy. First I would pull the coil packs and make sure they are clean of moisture. Then pull the plugs and make sure they are in good working shape... replace if needed. Try that before you go run out for coil packs because they can get costly.

And don't drive it.
Hmmm, I don't know if I should.... I'm afraid I'd screw something up.

Damn, they won't look at the car until Monday and I need it to get around....

Guess I'll just have to stay home this week end.
 

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Discussion Starter · #12 ·
I always tune up a car when I get it, regardless of the history. In your case I would replace all 8 spark plugs, go with the Ford Motorcraft factory ones. Then erase the check engine light. After that see what happens; see if it runs rough and see if the CEL comes back on. These cars are known for bad coils. If the CEL comes back on and you have the same cyl. 4 and 7 misfires. Move the coils to a different cylinder and see if the misfire moves. If it does, you know it's a coil.
The thing is, through the dealer I bought the car through I got a warranty. I'm afraid if I take it anywhere and get it checked/worked on it'll void the warranty. So I'm going to have to wait until Monday to find out what I'm going to do about it.
 

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The thing is, through the dealer I bought the car through I got a warranty. I'm afraid if I take it anywhere and get it checked/worked on it'll void the warranty. So I'm going to have to wait until Monday to find out what I'm going to do about it.
Um...you forgot to mention before that you had a warranty at the dealership. If that is the case take it to the dealership and they will fix it for free. No brainer.
 

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Discussion Starter · #14 ·
Um...you forgot to mention before that you had a warranty at the dealership. If that is the case take it to the dealership and they will fix it for free. No brainer.
But it's not a Ford warranty. It's a small time car lot. And its a supplemental warranty, one of the ones thats covered by a company, not the dealership. The thing is I have to wait until Monday to find out what their going to do about it.

Do you think it will be ok to drive until then?
 

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Do you think it will be ok to drive until then?
drive it, I would, the worst that will happen as it seems is terrible gas milage but I wouldn't take no trip in it but around town, to the store ect Mine was doing the same and I drove it for a week with it jerking, very annoying and ended up being the O2 sensor with a 1131 code.
 

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Whether or not the car should be driven while misfiring is mostly dependent on whats causing the misfire and how often the misfire is. Repeated misfires causes extra fuel to get into the exhaust and could later ignite. Head gaskets don't like detonation either. But most engines can take a little bit of abuse... enough to get to the dealership on monday but thats as far as I would push it.
 

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the ignition coils are pretty easy to remove,mark them with whiteout or any marker,you will need to know later which is 4 or 7.try to clean the plug wells before removing the plugs,to prevent dirt from falling inside the cilinder .i use compress air for this.i clean the coils with a rag and put some diaelectric grease were it contact the plug.remove the plugs,buy 8 ngk tr55(less than 2 dollars a piece).install them,install coils 4 and 7 in different locations this time.(if the coils are bad,the code will have a different cilinder misfire number corresponding to the new location.)if coils are good then you should be alright for the next 30,000 miles.copper plugs wear faster but BURN HOTTER.this are just my two cents.:happydance:
 

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extended warr are good idea in case of something major.they don't cover tune ups,if you have replace spark plugs before i don't see a problem.it will cost you less and it be faster.ups! i forgot to mention the antiseize,a little bit in the middle threads of the plug is alright.
 
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you could possibly drive it but if unburned fuel gets into the converters it could damage them. if your engine light starts flashing stop driving it right away.
 

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Discussion Starter · #20 ·
you could possibly drive it but if unburned fuel gets into the converters it could damage them. if your engine light starts flashing stop driving it right away.
Took it to the dealer this morning, as I was on my way the engine light started flashing! Hopefully they fix it right rather than fixing it to last long enough to where there no longer liable for repairs.
 
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