High idle at high elevation - Gen 2 Coyote

[GTBradley]

I have an appointment tomorrow with the tuner to look at my idle setting. My 2017 gen 2 Coyote currently idles at about 900 rpm at 5700 feet where I live, but when above 10,000 feet elevation it can be as high as 1500 rpm. I don't see anything online related to high idle issues regarding Coyote engines, so I don't expect much response on this, but if you have heard anything remotely related on this I'd appreciate feedback.

Thanks, Bradley.

[Al_C]

This is speculation on my part: There may be programming in the PCM to accommodate higher altitudes. An engine really needs to run faster at altitude in order to get enough oxygen. I've read that you lose about 3% efficiency for every 1000 feet. We don't have any of these problems in "the flat lands", but I know how much trouble I have breathing in the mountains. If my respiration rate increases at altitude, it makes sense that the engine's respiration rate (rpm?) would also need to increase. It will be interesting to hear what the tuner says!

[Bob Cowan]

Mine doesn't do that. Idle is the same everywhere.

The engine doesn't really sense that there is less oxygen at altitude, because the percentage of O2 is the same - 21%'ish. 21% at sea level. 21% at 40K feet.
It's the pressure that drops. It's like having a lower compression ratio. The reading on the O2 sensor is going to be the same. The sensor only reads percentages, not volume.

I've never driven a vehicle where the idle changes that much with altitude.

[Ducky2009]

I haven't taken mine to a higher altitude, but was on my motorcycle at over 10,000 feet and never has an issue. It didn't idle faster. It did get better fuel efficiency.

[GTBradley]

...It did get better fuel efficiency.
Ha! That's because you probably drive so darn fast that the wind resistance, or lack thereof, came into effect.:p

[GTBradley]

A short follow-up for those interested: the idle was fixed by the tuner and actually they should have been able to do this way back when I had it tuned originally. It appears to be idling at about 700 rpm now and it sounds so much better.

I haven't tried it above 10,000 feet yet though. I'll try to report back on that when I do.

We did have a short discussion about the honeycomb flow straightener that some use and the mechanic thought it might be a good idea as he thinks the intake tube doesn't give enough distance to the MAF sensor before the flow makes a turn.

[GTBradley]

I just discovered that the position of the MAF sensor is not optimal as I have it on the aft side of the spectre tube closest to the engine and it's generally suggested that it be on the outside or front, towards the radiator. The Coyote install manual has pictures of it installed on the side near the engine, but it does say in the text that you should position it "on the far side".

I found this discussion too: https://thefactoryfiveforum.com/showthread.php?31294-Coyote-MAF-Location-Orientation

[JohnK]

I also recalled reading that the MAF sensor should be on the outside of the tube, so I set mine up this way. In my case, this required adding a 12" extension to the harness for the MAF sensor. I used this one. (https://www.amazon.com/gp/product/B08FCVMT2N/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)

[GTBradley]

Interesting, I ended up cutting a bunch of zip ties all the way back to the ecu to get more slack in the wiring harness. Oh well, I guess I saved 25 bucks.