2.5L ('98-'01) Can I unplug exhaust-stroke firing plugs?

[Conflict]

2001 2.5
Anybody know which plugs are the exhaust-firing plugs? (all on secondary coil?)
Wouldn't you just have a normal engine if you unplugged them?

 

[superj]

i never thought about that but i suppose you would. try it out and let us know

 

[lowspeedpursuit]

The idea of "[unnecessary] exhaust-firing plugs" is a misunderstanding, both of why the dual-plug Limas have two sets of plugs and of waste-spark in general.

I don't know how the newer computers feel about it, but in '94, you could drive on the primary coil running mostly fine. But why? What are you actually trying to accomplish?

 

[sgtsandman]

I believe the secondary plugs are there for emissions purposes and really don’t contribute anything to engine performance. You still need something there to plug the holes, so I don’t much of a point in disconnecting them.

In any case, if I remember correctly, the secondary plugs are on the intake side but it has been a long time since I worked on one and had to worry about it. So, that information could be incorrect.

 

[racsan]

On intake side. Unplug the coil pack and it wont be firing the plugs. It is a emmison thing, supposedly burns off anything left in cyl on the exhaust stroke.

 

[lowspeedpursuit]

Before we get too deep here, the secondary coilpack doesn't "fire on the exhaust stroke for emissions reasons".
The secondary plugs are there to make sure all the gas gets burned, but that's both an emissions and a power thing. Putting metered gas in the engine and not burning it isn't just bad for the environment (and the cat), it's wasting gas and leaving power on the table.
Like I said, the idea that the secondary fires on the exhaust stroke comes from mixing up dual-plug and waste-spark.

Both coilpacks, primary and secondary, fire roughly together. Meanwhile, each coilpack has two coils inside, even though it serves four cylinders.
So, when one individual coil is firing, you get spark at two plugs: one in a cylinder on compression, and the other in a cylinder on exhaust. The spark in the first cylinder is the point. The spark in the second cylinder is "wasted". It isn't done for emissions purposes, it's just not a perfectly efficient ignition system.