I have an 03 V6 Mustang and while driving last week on the highway it started bucking uncontrollably while accelerating. After exploring similiar problems on other websites I have now replaced the plugs, wires, coil pack, and fuel filter. When test driving the car after replacing these things I have noticed that it runs like a top until it warms up. As soon as it starts hitting operating temperature it starts up with the "bucking" for lack of a better term again. Also it has never thrown any codes if that helps. If you have had any similiar problems and found something to fix it please let me know I have been racking my brain over it for a couple days now and the more I look online the more confused I get so I figured I would ask "the mustang experts"

 

What coil did you use? Its possible that you got a bad one.

 

I just used the OReilleys house brand for cost sake. I know you get what you pay for but any other ideas?

 

Swap it out, tell them it fails under load when the engine fully warms.

Worst case, warranty it out for a Borg Warner.
Thats the one I have and its been good for a year now and has a lifetime warranty.

You can also order the Motorcraft from them, go with that if you can afford it.

They will take care of you, I stopped shopping at Autozone because OReilleys treats me like Napa did back in California.


but for the time being you might just want to replace it with another one and see if it still does it if you are trying to save money. If it does not do it right away then thats your problem.

 

Ok I will try that tonight. Is that a pretty common problem finding a bad coil pack from off the shelf like that. Last night I changed the EGR Valve and TPS because I read other people have had problems with those. The EGR Valve was full of soot so I dont feel too bad about changing that and it seem to help slightly but, the TPS did absolutely nothing for it so it will be going back. I figured as much since it has never thrown a code. Any other sensor ideas if the coil pack doesn't work again? Maybe O2 but you would think that would definitely throw a code? Thank you for your quick response.