Last week I replaced my Bosch Iridiums with NGK Laser Iridiums, and the car seems to have lost its pep. It just doesn't slam your head back like it used to. The Bosch plugs were barely a year old, but I changed them because I realized that I hadn't gapped them properly, which I thought might explain my somewhat rough idle and acceleration vibrations. So I decided to just go ahead and replace them with properly gapped NGKs, which I believe are the same as the factory plugs.

So now when I push the accelerator, the engine revs nicely, but it doesn't seem to equate to actual power. It becomes even more sluggish if I've been driving for more than 30 mins, and the engine sounds strained.

What's going on here?

 

Not sure but I put the Denso Iridiums in when I changed mine, I am lead to believe that the Denso's are the OEM ones...

 

If its not tripping a code, then I don't think it's the plugs. The only thing they can do wrong is misfire...and the O2 sensors will pick up a misfire in no time at all. I'd guess you need to look elsewhere, since you changed them for rough idling to begin with.

 

Re check the new plugs are torqued down properly with the compression washer.

 

It started misfiring at stoplights yesterday, so I picked up a fresh set of the Bosch Iridiums I had in there before, swapped them out, and now the car is running smoothly again. By smoothly I mean its back to how it was before I put in the NGKs. And it seems the pep in the throttle has returned as well. Bad set of NGKs, or is NGK just crap? Who knows