Trying to track down a misfire in my wife's GTP.

Tried one step colder plugs and the idle got noticably worse even though this plug is recommended for cars with smaller blower pulleys.

She has a constant shudder above 2500rpm and a surge at idle.

Got worse with the colder plug. Do colder plugs require more juice to fire? If so that would mean one of her coils is bad.

 

No, a colder plug has the electrode sticking out a little further, that's all. As long as the gap is the same it will take the same amount of energy to create a spark.

 

The answer to your question is "no". The amount of energy it takes to fire a plug depends primarily on the gap and also on the environment (cylinder pressure, etc.) that the plug is in.

The previous two posts are in error. Colder plugs typically have shorter electrodes. The gap is set when the plug is installed, has nothing to do with cold vs. hot.

Rich Krause

 

See thats what I was thinking.

Thanx to everyone for posting.

I'll swap coils with my dad's Buick tonight.

 

Try removing 1 plug wire at a time from the coil pack, and laying it off to
the side. start the car. did problem get worse?
Did problem stay the same? Most likey you have a bad wire. When you have
a coilpack on the grand prix's go, you will have 2 cylinders not firing.

The easiest way to check, would be with a scantool, such as autotap or Tech
2.

 

Yeah, he's right
http://www.ngksparkplugs.com/techinf...000&country=US