2006 ST1300 / Temporary serious loss of power above 3000-3500 feet

I've had my ST1300 down in the Deals Gap area several times, on my last visit, the bike exhibited a serious loss of power as I ascended up past 3000 feet. As a fuel injected bike, I understand that the ECM will analyze and adjust the fuel mixture. I'm theorizing that I have a defective sensor. Does anyone know which sensor this might be as well as the location of it on the bike?

Thanks!

I'm thinking bad gas so I'd run some seafoam in it 1st... since it's a 2006, you might want to pull the tank up and take a look at the vacuum lines and T connectors and make sure they are clear of gunk. It might also be a fuel pump but I'd start with the other things first... if you have a bad sensor, the bike will usually throw a blinking FI light at you.

I would also think bad gas or a failing fuel pump would be your best place to start.

Need some more detail: Did the bike continue to be short on power above 3,000 feet? Does the power return below there?

The first thing to do is check the ECM for stored fault codes. If it is altitude-related, you want to look at the inside air temperature (IAT) sensor and manifold absolute pressure (MAP) sensors. You might also check the oxygen sensors, since those will have some bearing on the mixture as well.

--Mark

Seafoam...mmo...replace lines...clean T....check codes.....they don't always throw codes for clogged lines...try the easy and free stuff first before you start throwing $ at it.

I'm pretty sure you need to turn the key off and then on again for the ECM to adjust to altitude.

Throttlejockey said:

I'm pretty sure you need to turn the key off and then on again for the ECM to adjust to altitude.

Click to expand...

The Smokies aren't the Alps but I've never had any issue like this in numerous trips to the area. It's not unusual to go from 1800 feet to 6000 feet and anywhere in between in the span of a few miles with no fueling issues. The only sensor that I think is sensitive to density (altitude) is the MAP sensor and failed it should trigger a code and illuminate the FI light. Clogged vacuum lines and tee would only affect idle and off idle response. Does it do this at one spot in the rev band, like a dip in power, at 3000 to 4000 rpm, then return to normal?

Throttlejockey said:

I'm pretty sure you need to turn the key off and then on again for the ECM to adjust to altitude.

Click to expand...

Mixture adjustment is continuous on every FI system I've ever heard of that has pressure and temperature sensors. There wouldn't be any point in measuring the manifold pressure once and using it for the entire run of the engine. Even how fast you're moving has some effect on it.

--Mark

I think this is where I saw it.
https://www.st-owners.com/forums/showthread.php?119383-My-ST13-runs-different-at-high-altitude/page2

I know when I was out in MT on Beartooth my bike was running weird and turning the key off and back on solved the problem.

Thanks for all of the input guys! I've had my '06 down there several times only experienced this power loss during the last trip. It happened as I ascended up onto the Cherohala Skyway. I rode from the Deals Gap end down to Tellico Plains. At that point, I was below a quarter tank and refueled. The power loss happened a couple of other times during the trip at altitude, so I'm ruling out bad gas as I refueled multiple times from different gas stations. I did major maintenance just prior to the trip, which included an oil change, final drive oil change, new air filter, etc.

Is there a single sensor that provides the altitude data to the computer, or are there multiple sensors. Is there a "code reader" for the ST at a reasonable price?

Thanks again...