Spark plug fix & gas mileage?

[BSD]

So after reading the spark plug gap thread I decided to check mine. Unfortunately, my spark plug socket was too wide to finish the job but I did check the coilpack and #2 and #4 (IIRC) had the springs bound up. Poked it with a screwdriver and all was good. Since then my throttle response has improved as well as low end power with the tune turned on. That said, my indicated MPG has dropped about 10 mpg. I used to get mid to low 30s now I'm in the mid-high 20s. Mostly city driving with lots of short trips. I have since been threw one tank like this and I read something about a full tank resetting fuel trims but I can't remember where. It doesn't seem like it's reset yet.

Thoughts?

 

[Swordsmith]

A 10 mpg drop sounds like something went seriously wrong.... too seriously for anything I can think of.

Do you hand calculate tanks, or just rely on the display? The display is notoriously inaccurate and I suppose it could have somehow gotten it's signals or sensors messed up enough to cause this.

Another thought is that if you have a datalogged tune, it may have been set way off in order to compensate for your misplaced coils, in which case, having fixed the coils you may now need to datalog and get a fresh tune.

10 mpg though, still seems shockingly far off; two or three, I would attribute to any of those problems. Ten? Wow.

 

[BSD]

I have been going off the display. The few times I've hand checked it was only off by a little more than 1.

I went for a joyride today and it's the first time in weeks since it's been driven longer than 15 minutes. DIC said 31mpg for a ride that normally gets around 34-36. This was with the tank full and the DIC reset.

I'm thinking it's the tune as well. One thing I noticed today is that my ultragauge was alternating between open and closed loop while cruising and would switch to open when I really stomped on it. I don't remember ever seen open loop while driving, only when it first started up. I checked the MAF as well as any other sensors and everything looked good.

 

[Luv2xlr8]

Do you get the open loop while driving when you let off the gas? Mine does that as well only when I let my foot off the gas around 2000rpm which is normal.

 

[BSD]

No, if I let off the gas and cruise or drive easy I stay in closed loop for the most part. I don't recall it doing this before messing with the coilpack, but I might not never noticed.