"Reduced Engine Power" when using regular fuel

[KDWH]

This is kind of wierd. I purchased a 2003 Yukon XL 2500 4x4 last April. And i have noticed that whenever i put in regular grade fuel the engine will act up about 100 miles into the tank. It will go into Reduced Engine Power mode and throw codes for rear knock sensor - low voltage, throttle position sensor, pedal position sensor. Then after I clear the codes they will come right back until I put in mid grade fuel. Then it runs like a champ with no problems whatsoever. Does anyone know what could cause this? I have just put in the mid grade fuel and gone over 10,000 miles with no issues. I tries another tank of regular and the codes all came back?

Vehicle has 185K miles with the 6.0 Liter engine.

 

[ezdaar]

Its probably tuned for best fuel.

stop putting that cheap crap in it and run the best you can.

 

[OR VietVet]

Regular fuel burns at a quicker rate and can cause engine ping and the knock sensor will retard timing and cause power problems. Mid grade or premium fuel burns at a slower rate and therefore will not ping. The ping is caused by the hot surface on top of the piston igniting the faster burn/ignite regular fuel and those explosions are the ping before the spark plug ignites. Premium fuel or mid grade, burning slower, will not set off the knock sensor and then retard timing.

 

[PinkAle]

What they said that's the reason you can't run anything lower than 91 octane in a Bmw but I think you can have a mechanic change the timing so you can run the crap fuel if you really feel the need too

 

[KDWH]

Sounds good. I will just stick with the good stuff. Thank you all for the quick feedback.

 

[OR VietVet]

If the mid grade fuel works with no ping then use it.

 

[Shadow17]

Yep, happened to mine too. There is even a sticker on the gas cap that says premium fuel required. Yep, I use 89 from now on.

 

[ccapehartusarmyINF.(ret)]

keep in mind octane rating has nothing to do with the quality of the fuel