Less Torque After Changing Spark Plugs?

[TowPow]

I recently changed the spark plugs in my '98 Explorer 4.0 SOHC to try and fix a pinging problem during cold starts.
Pinging is still there, but better, and my MPG has skyrocketed.

However, whenever I tow my 1300 lb boat and trailer it feels like I am STRUGGLING to accelerate! Before I changed the plugs I could zip around no problem towing the boat, even with five people in the car, a full ice chest, extra tank of gas and everything!
Now it seems like I REALLY have to give it some gas to get going and I don't even come close to the low-end torque I had before!
It feels like I gave up truly impressive torque for a more horsepower-oriented engine...

Did I mis-gap the plugs? Is this how the engine is supposed to operate? What can I do to help out with this? Do I need to do one of those "re-learning idle" cycles like after a battery change?

 

[Lube]

If you're having a pinging issue, it's probably not related to your plugs, particularly as it was there before and after you changed them. I'd run it over to Oreilly, Autozone etc. and have the codes read.

When the knock sensor is triggered, the computer will pull timing advance out of the ignition. Reduced spark advance = poor performance.

 

[SoNic67]

"Gapped"? Why? If you would use Autolite XP103 you don't need to do anything to them.
I would suspect that the spark advance/timing is off now (less advance usually means better MPG in no load and worse torque).

 

[Lube]

"Gapped"? Why? If you would use Autolite XP103 you don't need to do anything to them.
I would suspect that the spark advance/timing is off now (less advance usually means better MPG in no load and worse torque).

Plugs always need the gap checked before installation no matter whose they are, as they can change from rough handling in shipping. Think UPS here. Also, retarded timing can lead to a severely overheated engine in short order.

 

[TowPow]

Thanks for the replies and info, everyone.
A couple of things, though: the OBD isn't giving any codes at all. pinging, timing, or otherwise. No CEL

I'm also not seeing any overheating at all.

What the heck is spark advance and how can I correct the issue that I seem to be having with it? How will I know if it is indeed the spark advance that is the problem?

 

[Joe Dirt]

What plugs and part number/gap did you install? Did you put in new wires as well?