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I've got a 00 gt ... Previous owner told me he used the car on road tracks and before he sold it he took out big injectors put factory ones back in. So when I recently had it running like crap it had a code for mis fire cylinder 5. So at that point I talked wife into spending a few bucks for bigger injectors msd coil packs and new plugs. Yes it has a performance intake and throttle body on it. Didn't run right when done. I reset computer .. No help. New cam position sensor no help. 3 new injector connectors it started idle good for about 3 mins then went back to surging and when trying to move it it has a severe miss and you can smell fuel in exhaust... I've got no vacuum leaks everything is hooked up... Where do I go next??
 

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Well if you didn't tune the car for those bigger injectors then that's one reason... Computer is expecting 19lb injectors. The intake and throttle body could be causing issues too, no reason to replace the stockers, they aren't restrictive. MSD coil packs are a downgrade from stock. Very likely all you had to do was rebuild the coil pack in cyl 5 or replace the spark plugs.

Put it all back to stock and hope the wife doesn't find out that you just spent all that money for no reason...
 
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Discussion Starter #3
I've got a 00 gt ... Previous owner told me he used the car on road tracks and before he sold it he took out big injectors put factory ones back in. So when I recently had it running like crap it had a code for mis fire cylinder 5. So at that point I talked wife into spending a few bucks for bigger injectors msd coil packs and new plugs. Yes it has a performance intake and throttle body on it. Didn't run right when done. I reset computer .. No help. New cam position sensor no help. 3 new injector connectors it started idle good for about 3 mins then went back to surging and when trying to move it it has a severe miss and you can smell fuel in exhaust... I've got no vacuum leaks everything is hooked up... Where do I go next??
And what makes you say that??
 

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Where to begin?

MSD stands for "My Spark Died". Or "Might Suddenly Die".... Not a good reputation for reliability. The OEM Motorcraft coils are considered to be the best coils for these engines.

Not sure which size "bigger" fuel injectors that you used, but the largest size that you would ever need for this displacement engine, normally aspirated, are 24 lb injectors. And you need a custom tune to be able to use anything other than the stock 19 lb injectors.... Which, for your particular application, are perfectly capable of supporting all of the horsepower that your engine is capable of producing.
There is nothing to gain by increasing injector size. The larger injectors are the main cause of the problem that you describe.

If you reinstall the stock injectors, it will make it much easier to diagnose any misfire that you may have.
 

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