Mach 1 engine hesitation/ cracking noise from rearend HELP!?!!!

[Torchredmach1]

I have a 04 Mach 1 with 72k on the clock. For the past couple months I've been having an engine hesitation problem at WOT. Anything above 4k rpm the engine shakes and hesitates very bad. When this happens I can hear a cracking noise coming from the rearend..or the exhaust I assume not the rear axle itself. It cuts a ton of power. I've already tried fuel injector cleaner and it helped a little bit at low rpms but not at WOT. Anyone have a similar problem or a possible solution!??? Trying new spark plugs next as I'm still running the original plugs. Any help would be much appreciated!!

[Dennis O'Shea]

I am no expert but 72k on the orginal plugs seems to me to be an awfully long time for a set of Plugs I only put a season on the little car and after sitting all winter the plugs get changed It may be over kill but it runs very well But I also change the Oil every 2500 miles too I know I am anal old fart.Good luck I hope you find the problem

[Torchredmach1]

Yea true I know I've been slacking on the spark plugs they need to be replaced. Hopefully it does the trick!!

[LILBLKSNAKE]

coil packs???

[Torchredmach1]

I ordered NGK performance spark plugs last night so I'll put those in next week when they get here. I want to make sure the coils HAVE to be replaced before I go spend $400 on a MSD pack should they be replaced?? I don't have a lot of money to spend..the Mach is an expensive ride...especially the gas

[Mustang5L5]

72k is not a long time for platinum plugs. You can change them if ypu want, but normal maintainence intervals for plats are usually around 100k.

I just did mine on my daily driver at 85K miles and they still looked brand new.


Copper plugs are a different story, but they haven't been OEM in quite some time.

[Cobraman1024]

I ordered NGK performance spark plugs last night so I'll put those in next week when they get here. I want to make sure the coils HAVE to be replaced before I go spend $400 on a MSD pack should they be replaced?? I don't have a lot of money to spend..the Mach is an expensive ride...especially the gas

The individual coils in a coil on plug ignition system should not be replaced unless you measure "open" resistance between the two terminals on the electrical connector part of the coil. If one of the coil on plugs has failed, I would replace it with an OEM coil before putting out the money for an MSD set. There have been reliability issues with the MSD coil on plugs. Other aftermarket performance replacements include GMS and Accel.

[LILBLKSNAKE]

I would replace it with an OEM coil before putting out the money for an MSD set. There have been reliability issues with the MSD coil on plugs. Other aftermarket performance replacements include GMS and Accel.

A lot of drivability issues actually stem from bad AFTERMARKET COP's. Nothing better than OEM ones. Do a search on SVTPerformance.com

[Cobraman1024]

A lot of drivability issues actually stem from bad AFTERMARKET COP's. Nothing better than OEM ones. Do a search on SVTPerformance.com

Yeah, I've known about the common aftermarket COP failures for awhile now----ever since I bought the Mystic actually and started looking into the coil on plug conversion. The OEM coils are very good and don't need to be "upgraded" until you are are doing a very serious high performance build on the 4.6 DOHC engine.

[LILBLKSNAKE]

Yeah, I've known about the common aftermarket COP failures for awhile now----ever since I bought the Mystic actually and started looking into the coil on plug conversion. The OEM coils are very good and don't need to be "upgraded" until you are are doing a very serious high performance build on the 4.6 DOHC engine.

There is a guy selling a complete COP conversion harness for 96-98 COBRA's. I think it was on SVTPerformance.
Basically you buy his harness and a set of coils.