Intermittent fuel mileage drop

[speeddemon2588]

Hello All,

Recently I have noticed sudden and inconsistent fuel mileage drops from tank to tank. I just pegged 27k running a PC3 USB with out FCE or ECU re-cal.

One week I can be averaging 32-35mpg mixed riding, then upon next fill up I can barely manage 25. I'm racking my brain as to what would cause this? Perhaps a faulty PC or brakes dragging from being dirty? Maybe just poor fuel quality? Perhaps out of spec valves? (Unlikely as the fuel drop would be consistent, I would think

I have plenty of power everywhere and I haven't noticed a change in performance. The only correlation I have started to notice is a problem with the cold start high idle. Sometimes the bike starts with the high idle as it should, other times it starts idling at less than 1k rpm and is prone to stall. Maybe I'm having a problem with the idle control valve holding a proper mixture?

Any insight from any of you would be greatly appreciated.

Thanks

 

[delbert]

Hi not sure about your gas mileage , but the idle control is a thermowax unit that controls the air flow to compansate for the extra fuel at cold start hence raising the idle to stop stalling so once warmed up should have no effect on the running ,, they do tend to stick as you describe and can be easily removed /stripped and cleaned.

 

[Dreamdemon]

You are in CA when your near the ocean it might be temperature related. I assume you use an o2 eliminator plug with the PC3. I had changes from 40 mpg to 35 mpg when I installed the PC V in winter or when the temperature changes very much. In summer I only had the problems when I hit the fog at the coast.

Also check your sparkplugs and connectors. Intermittet problems are usually an electric problem so it could be anything (sensor, injector, cable, ingnition ect) and will be time consuming to find when it does not break completely.

 

[speeddemon2588]

You are in CA when your near the ocean it might be temperature related. I assume you use an o2 eliminator plug with the PC3. I had changes from 40 mpg to 35 mpg when I installed the PC V in winter or when the temperature changes very much. In summer I only had the problems when I hit the fog at the coast.

Also check your sparkplugs and connectors. Intermittet problems are usually an electric problem so it could be anything (sensor, injector, cable, ingnition ect) and will be time consuming to find when it does not break completely.

Thanks for the reply guys.
I expected a bit of a drop, but not below 28mpg. Water temp is 158F while I'm riding, so she is running cold. However, after two days of running with out the PC3 my mileage is back around 32. So I'm guessing its a Power commander failure as I was already running a stable map for months before I noticed the issue. I've had two PC3's that failed the same way on my GSXR back in the day. Bummer they don't last much more than 5yrs.

 

[Lonney]

Thanks for the reply guys.
I expected a bit of a drop, but not below 28mpg. Water temp is 158F while I'm riding, so she is running cold. However, after two days of running with out the PC3 my mileage is back around 32. So I'm guessing its a Power commander failure as I was already running a stable map for months before I noticed the issue. I've had two PC3's that failed the same way on my GSXR back in the day. Bummer they don't last much more than 5yrs.

Yeah i had one go and mine was cutting in and out which really made it hard to detect.

 

[jared p]

Thanks for the reply guys.
I expected a bit of a drop, but not below 28mpg. Water temp is 158F while I'm riding, so she is running cold. However, after two days of running with out the PC3 my mileage is back around 32. So I'm guessing its a Power commander failure as I was already running a stable map for months before I noticed the issue. I've had two PC3's that failed the same way on my GSXR back in the day. Bummer they don't last much more than 5yrs.

they dont last much longer than that no. however sometimes you can get away with finding a dynojet dealer, having them verify it's faulty, and you can have them send it in to dynojet who will fix or replace it for you at a nicely discounted cost

 

[speeddemon2588]

they dont last much longer than that no. however sometimes you can get away with finding a dynojet dealer, having them verify it's faulty, and you can have them send it in to dynojet who will fix or replace it for you at a nicely discounted cost

Thanks for the info. I never even thought to try that.