1997 mustang cobra problem please help

Makobra

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get the exact time it takes for it to start running bad. time it and post that time here.
 

Phillip Scocca

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My brother had friend who’s a mechanic come to the house they compression tested it said it was good he said the wiring harness ? Any idea if that would do this to the car
 

Makobra

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well crap. you've gotta put a computer on it and see what its doin, man.
 

Makobra

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swap the coil pack on that cylinder and if it continues disconnect the fuel injector wires from the injector on that cylinder.
I suspect you have a leaky or bad injector or a bad coil.
 

Makobra

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if your compression is good and your coils are good and your plugs are good when that only leaves the injector being bad.
there is no such thing as a "dead cylinder". all you need to run is compression, fuel and spark.

disconnect the injector and see what happens. if nothing changes or it just runs worse then i'd put money on that.
 

Phillip Scocca

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if your compression is good and your coils are good and your plugs are good when that only leaves the injector being bad.
there is no such thing as a "dead cylinder". all you need to run is compression, fuel and spark.

disconnect the injector and see what happens. if nothing changes or it just runs worse then i'd put money on that.

The injectors were done last year and were just recently cleaned another code came up p0351
 

Makobra

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The injectors were done last year and were just recently cleaned another code came up p0351

Code says bad coil, car acts like bad coil, I say it's a bad coilpack.

I'd pull the plugs and put a scope down the cylinders. One will probably loook quite different. Might even be a clean spark plug if they were new when this happened.
 

Phillip Scocca

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Code says bad coil, car acts like bad coil, I say it's a bad coilpack.

I'd pull the plugs and put a scope down the cylinders. One will probably loook quite different. Might even be a clean spark plug if they were new when this happened.

Both coils packs were replaced also swapped them and still throws number 8 misfire
 

Makobra

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unplug the coil pack on number 8 and see if it says the same thing.
also, get a camera from harbor freight and look in the cylinders.
 

Makobra

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you are looking for the cylinder that looks different. each cylinder should look the same. if you have one that isn't firing at all or is randomly firing it'll look either a lot cleaner (because gas will be acting as a solvent) or it might look VERY dirty because the fuel mixture is wrong for that cylinder so maybe excess soot compared to the other cylinders. its hard to explain but in general when troubleshooting systems what you need to look for are differences between similar things.
 

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