New plugs, synched TBs = less mpg???

[Michael-NC]

Changed spark plugs to iridium ones (gapped properly) and synched TBs. Checked TPS position and it is OK ("-" in the middle). Engine runs smooth, great idle, pulls strong, no complaints there. However, before plug change and TB synch I was getting 41-44mpg not pushing it, now it is 33-36mpg, same riding style, same PC3 map. It's an '03 with HMF slip-ons. Tried other maps and still ca. 8-10mpg less than before. WTF? Thanks for any advise.

 

[greyrocket]

if your getting over 35 thats doing good. i get maybe get 30mpg

 

[redvoodoo]

If I take it easy I maybe average 35. At 165 mph I only am averaging around 10.

 

[omslaw]

My MPG is about the same; 35-ish.

Strange as it may sound, I think the iridium plugs may be causing some of it.

When I switched to iridiums (first plug change), my MPG dropped immediately. I didn't change anything else but the plugs. I then went and bought some stockers and pulled the iridiums...my MPG went back up.

Perhaps it was the moon-phase or sun-spots, but I noticed a difference... BTW, FWIW, a buddy of mine noticed the same thing when he installed iridiums

 

[RC Randy]

I just did the first plug change on my 02, and used the Iridium's, and also sync'd the throttle bodys. Still getting 41-42 mpg. Stock except for Akra bolt ons.

 

[TXBusa05LE]

Strange as it may sound, I think the iridium plugs may be causing some of it.

+1

 

[TallTom]

Had the same problem. Reset the ECU. Fixed mine. I get better than evr mileage now.

 

[SANDFLEA85]

I get 23-28mpg depending on how i ride,i just changed my plugs (stock plug) although im mapped 10% fat because of NOS..my bike runs/idles smooth as silk...

 

[Spudley]

Also check for vacuum leaks...where the air box, "seats" on the throttle bodies and whether all the vacuum lines were assembled properly. No offense, I'm sure you're a good wrench. Just offering ideas. BTW, I still run the CR9E's, every 7,500, now at 26,500, no complaints.........

 

[Michael-NC]

Thanks for your replies, I will try going back to stock plugs and see if mpg improves, this sucks, I was expecting an increased or equal mpg and not less with iridium plugs in.