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Topic Review (Newest First)
05-28-2013 12:34 PM
sailor Reading the rest of your comments today, I'd doubt you'd mix up the warnings! Had to ask just to confirm 'cause that confusion when something happens suddenly has been seen before...

Mike's answer sounds like a real possibility. I'd guess that even if it samples continuously, there would be a "lag" built in to avoid making changes too quickly trying to respond to transient variations in air pressure (averages over time) & that steep grade fooled it.

At least you don't need to have the car re-tuned for high & low altitudes, as was the case before electronic systems!

Cheers!
05-27-2013 11:14 PM
mikebontoft it could be possible. I imagine you never fully turned your key to the off position? they used to only sample at initial key on engine off (KOEO) so you were probably screwed since it never reset. maybe on the last try you went all the way. who knows lol.
05-27-2013 10:05 PM
spongebue Ok, cool. Heh, that reminds me of when I took my other car through the mountains for the first (and only) time. 1995 Oldsmobile Cutlass Ciera. Morning of 4th of July, a few weeks before I bought my Focus. I was on the same hill, but the opposite direction (westbound, better known as "down" in this spot). Got out of the tunnel, and spent the next few miles braking to keep my speed under control. Then my friend commented that my battery light was on. I noticed that my oil light was on as well. Oh hey! What do you know! I have no power brakes or power steering. Wonderful.

If there was a typical weekend traffic backup or ice on that highway, I'd be screwed. I was using quite a bit of force on the pedal just to maintain my speed. Popped it into neutral, tried starting up again. Nah. He didn't really feel like it. Turned off radio, climate control, etc to keep my battery conserved in case there was an alternator issue or something (remember, my battery light was one of the first things I saw). ~20 seconds later, try again. Nothing. I felt the "4 C's" needed for air traffic controllers (cool, calm, collected, and in control) but my friend (who actually went to ATC school) said it was the scariest thing he's ever been through. My speedometer acting funny with the key off didn't help. Finally, about a mile before the exit, I try for maybe the 4th time. Success.

Filled up the gas tank, and went to Burger King to get a bite to eat and catch our breaths. Friend insisted on paying for the fill-up despite my best efforts, and I think he was surprised at how much it took (probably 13.5 gallons, most I've ever seen it take was 14.5). He later asked if it was possible that there wasn't much gas in the tank, so it was tilted away from the fuel line on the steep hill. Given that it ran pretty well on the way home with a full tank (just felt underpowered due to the bigger engine needing more air, heavy car, and steep incline) I think that's most likely. Then again, if it only took its sample in the beginning, I would have expected it to cut out when I was trying to get up to the tunnel, not when I was idling down.

Thanks for your help, everyone!
05-27-2013 09:55 PM
JFrye Thats good information to know. Thanks for pitching it so we can help him get it figured out.
05-27-2013 09:42 PM
mikebontoft Yeah it happens a lot to vehicles making that transition in CO. Older Fords used to have the same trouble on descent. What happens is the barometric pressure sensor (doubling as the map sensor at the time) reads only at engine start-up. You'd shut it off (if it didn't die on its own) and it would fire right up and run great until the same drive is made.

I believe the sensor makes multiple samples now. I think that was their fix. So essentially when it started running like crap for you, it took another baro sample and corrected itself.
05-27-2013 09:24 PM
JFrye Im not expert on this, but it makes sense to me. If Im wrong, hopefully someone else can pitch in and help get you the right answer.
05-27-2013 09:18 PM
spongebue Right, that's what I was thinking. To give an idea of what the car was going through, the oxygen concentration in the air goes down 1.1 percentage point (7.5% if my math is right) - 35 percent less than what you'd get at sea level. Normally I'm in Denver (5280 feet :) ). It may not be a huge amount, but it was over the course of a few minutes. Plus, I came from Steamboat Springs, CO (with a few stops in between) - lots of altitude changes on that route.

That's all based on this chart: http://www.higherpeak.com/altitudechart.html
05-27-2013 09:09 PM
JFrye I would think it would have to do with the air temperature and density that high up. With the air going into the engine has changed, then it throws off the air fuel ratio and the computer tries to quickly adjust for it. (<- just an idea, and I may be completely wrong here) If the vehicle is used to being driven in those conditions, the computer may need to relearn for the sudden changes.
05-27-2013 08:24 PM
spongebue It wasn't super hot out as I recall - just gets warm and stuffy inside when it's sunny and you've got a black interior :D

It was the yellow check engine light that went on. The same one that would tell you that there's an OBD diagnostic code waiting. But again, it was just flashing briefly, and went off on its own. The manual tells me that that signals that the engine is misfiring. Ultimately, I mostly want to be sure that there is no long-term damage to be mindful of, and if there are any tips to prevent it in the future, that would also be great.
05-27-2013 04:48 PM
sailor If the warning happened to be the exclamation point (!) it would be for transmission overheat most likely, and that would reduce power then recover as soon as it cools a bit.

A/C being on & a hot day would make that more likely.

Just a guess, you can confirm which warning lighted up & folks will continue throwing out possibilities.

Cheers!
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