So, I bought an '05 DB ZR 6MT (~50,000 Miles) back in January and thought it would be smart to do some preventative maintenance and have a good "starting point" for my ownership. I swapped the front brake pads, windshield wipers, & oil in Feb. A couple weeks ago I swapped out the spark plugs (yes I know the stock ones are supposed to last 100K, but I figured I'd give myself a baseline for everything).

Anyway, after the swap I noticed a decrease in gas mileage at lower RPMs and a sporatic "jump" to the car when running idle . I find it very interesting that I can experience 20-23 MPG at highway speeds in 5th and 6th, but at an idle my MPG is dropping down to 15.5-18 .

Any thoughts? Could this have something to do with my installation of the plugs? Could my installation have just been the "straw that broke the camel's back" for a larger problem?

I plan on going back and re-performing the whole procedure for replacing the plugs to see if I may have missed something the first time around, but if that doesnt help I am not sure what to do. Any help/advice would be appreciated. Thanks!

 

Did you gap the plugs and what gap did you set it to.

 

Sorry, I guess the plug info would have been important to post --

I bought NGK Platinums, which I was under the impression are pre-gapped and ready for installation since you cant really gap them yourself without stripping the platinum off.

 

Plugs are gapped improperly
Crush washer on plug is not sealed properly. THe crush washer fell off

 

gotta be the gap or a bad plug. any pinging or misfiring? maybe you didn't seat the coils properly?

 

Its good to hear that we are all on the same page. I just got back from bowling tonight and the car felt like there was mis-firing on 1 of the cylinders. Its been raining down here in Va Beach for the last couple of days, so next time its clear skies I am going to get out there and check each of the cylinders.

I didn't notice whether the crush washers on the plugs were "connected" or not. Should I go out and try to buy 6 new crush washers and replace each one as I check it?

 

Its worth checking but i wouldnt buy until i did. Also you getting a CEL? Maybe you swapped the order of one of the coil packs i think everyone has done that once in their life time especially with older style plug wires. Oh yea are the NGKs factory gapped at the factory recomendation?