skips under hard acceleration...bad mil?

NYBLKSTNG

New Member
Aug 18, 2009
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New York
98 mustang GT skips and runs rough under hard acceleration. Last fall the dealer said that I had a bad mass air. I have since replaced (used) and the car runs no different. Checked wires and plugs, replaced fuel filter and added dry gas. There is no check engine light on, mostly becasue I believe the mil eliminators...What are the symptoms of a bad mil or bad coil pack?
 
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A bad MIL would probably result in an MIL but it wouldn't cause running problems.

If the plugs and wires are okay and you're seeing misfires (from the sounds of it), I'd next check the coils.

It's surprising you're not seeing a MIL for misfire. It doesn't flash when this is happening?
 
Is the easiest way to check a coil to unhook a wire at a time and run the car lookin for any changes?
I used to get the MIL's last summer but none as of this year. If I rev the car hard it is like the motor takes seconds to catch up, with nothing but the sound of suction through the cold air. The car has days when it will "spool" up quickly and other days when it seems to take forever to reach redline. If I stay out of the accelerator you would not notice that it had an issue....
 
Is the easiest way to check a coil to unhook a wire at a time and run the car lookin for any changes?

For certain failures yes. In your case, I doubt you'd identify a bad coil this way as it appears to be firing the spark normally under minimal load and failing when the voltage requirement goes up (i.e. when cylinder pressures increase due to large throttle angles...)

I'd try to get a scanner on it even though you're not seeing an MIL (yet) to see if any misfire codes (e.g. P030x) are stored or pending. You might be able to identify which coil it is by determing which cylinders are showing misfires and deducing the coil by tracing the wires back.