Just replaced my worn iridium with some ngk copper. I found that the new plugs gave a very good response but the car seems to be running richer. Got a "plop plop" noise from my exhaust when letting my foot off throttle. Fuel consupmtion drop from 28.7mpg to 26mpg Anyone experience something similar to this? Could it be the new plugs change the ignition timing? Will a reset of ecu get my original gas milegae back?

 

Did you gap them before putting them in?
I wouldn't trust just the stock setting, even with those little paper sleeves.

 

No, I bought the one pregap to 11mm. Will the gapping result in such a difference?

 

Bigger gap could hurt. 11mm is almost half an inch!!! Did you mean 1.1mm?

1.1mm is .043 inch, the turbo guys all run .028-.030, I think stock is .032? Anyhow yeah you have them gapped wrong but I'd be surprised to hear that you could measure a difference.

-Chris

 

DOH! You are right, it is 1.1mm pregap from NGK (BKR6E-11) not 11mm. My car is not turbo charge, only with I/H/E.

 

I ran pre-gapped BKR7E-11's for a week (didn't have a gapping tool, doh!) replaced them with gapped ones. I couldn't tell the difference. *shrug*

Oh well, yeah, no ideas about your fuel consumption. Plugs don't change timing or fuel.. unless one of them is horribly misfiring, then you might end up running richer, or at least consuming more fuel.

 

IMO, just switch back to stock platinum.