I just bought a 2000 Harley w/supercharged 5.4 It has a Diablo chip and mafia. it runs great but gets 17 mpg. The original sticker says it should get 19. (this is on the interstate) so I took the chip out and the mafia off, but it won't run. It tries but that's all. ANY IDEAS???

 

I'm not sure how to fix your running issue, but your lucky to even be getting close to 17 mpg. My brothers 2001 5.4 and my 5.4 both get between 12-14 mpg, and I would think that it would drop with the supercharger. Plus, the window stickers on the new ecoboosts say they get 28 mpg, and they dont unless they have the perfect driving conditions. I think you should put the tuner back on and be happy with 17.

 

Do you really believe the sticker on getting 19mpg? 17 is pretty good and mpgs is all in how you drive, maintain your vehicle, where you live, warm ups, idling, and where you get your gas.

What chip did you disconnect?

The mafia is used to help recalibrate the maf.....when you took that off did you plug the other loose end back in to the maf?

There might be a performance maf installed also and that's why the mafia is being used.

Who knows what the previous owner(s) have had done to the truck?

You could be playing with fire here......disconnecting add on mods that you know nothing about......just a fair warning....

 

I've been modifying cars for 25 years. The only mods were the chip, mafia, flowmaster cat back and the egr is disconnected. That's all. I have always gotten more than what the window sticker had on it. What do you think about the egr. Maybe that will help the mpg's.

 

is the "theft" light flashing while its trying to start?

 

Take care and enjoy!

 

Nop on the theft light. The check engine light is on.

 

Yeah, an 11 year old truck with performance mods and you expected it to get what the factory ratings were? It's hard enough trying to get a brand new truck to do that....

 

19.5 mpg All stock

 

If your gas has ethanol, there's 1.5 mpg and if you have bigger tires than stock, there's some more.

 

#1 why are you trying to blow your motor???

#2 common sense proves that the truck was tuned to the non factory installed parts and when you removed the tune it's obviously not going to run right...


17 mpgs on the highway without the driver mod isn't terrible, expecially with a supercharged truck


#3 put the truck back the way it was and don't touch it again unless you have someone around to keep you from doing something stupid

 

MD, did ya try putting everything back in that you removed, and see if it starts?

Did ya pull the neg cable off the battery and flip the headlight switch to see if maybe you can reset the thing? Couple easy places to start.....

 

I put the chip and mafia back in and it runs fine.
I was just wanting to see what kind of mpg I would get without those pieces.
Thanks for the folks that are tring to help. Maybe the smart mouths just don't know much about cars but want to say something.

 

Actually they know more than you and you should sit back and learn. There are really great people here willing to help those willing to take their advice.