Trouble starting at high elevation

I have a 2011 sr5 with the v6, been having a hard time starting at high elevation recently. I live in SLC at about 4000 ft elevation, starts just fine at home regardless of outside temps but if I head up above 8000ft to one of the local ski resorts the truck will crank but doesn’t want to turn over at first, turns over after a bit of cranking or on the second try. At first I thought it was cold related but that doesn’t seem to change anything. Any ideas what this could be? All suggestions greatly appreciated

 

Could be you need to clean the MAF sensor. May not be reading enough air coming in to start. That's a wildly uneducated guess but I would start there. Tell us about your maintenance.last time you did a Plug change , air filter change etc.

 

Thanks for the idea! Spark plugs were changed about a few weeks ago, didn’t seem to change anything at high elevation. Battery is less than a month old, not sure about the air filter I can’t remember when that was done last.

 

check to see what your ECM thinks the atmospheric pressure is and compare to a known value, could be a bad or drifting Barometric Pressure Sensor. The ECM uses this information to make adjustments to fuel trim and engine timing.

For every 100 m (328 ft.) increase in altitude, pressure drops by 1 kPa (0.15 psi).

 

What I've found is that my truck likes the throttle to be opened somewhat at high elevations when it's started. If I do this it always starts the first time; if not, it struggles. Not floored, but like a 1500 RPM type position. This makes sense since the atmospheric pressure is significantly lower and therefore less air is entering the combustion chamber.

 

I think that's in your mind. Holding your foot on the throttle doesn't do anything before the truck is running. It will establish the idle position through the ETCS, which is determined by the ECM. The sensor that monitors barometric pressure should compensate for that signal to the throttle actuator.

 

Dunno, it works for me. My truck always starts no issue at up to 5k ft elevation on the first try, no foot on the accelerator, no issue. If i'm 8-11K feet it will often start for a second, and then die. Try again, and it cranks fine but nothing. If I open the throttle (yes, I know it's by "wire") it will start every time.

 

that's strange, but hey it if works keep doing it! I could see that being required in a carbureted vehicle but seems odd for fuel injection with injectors and spark controlled by ECM.

 

The described symptoms seem like related to the starter circuit and not the fuel injection system.

Suggest to check the battery connections and the entire starting system.

Or am I understanding your description incorrectly?

 

Ha great minds think alike. I wonder if we have seen the first barometric pressure issue controlled by that little, but expensive, pressure sensor located near the back of the engine.