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High Altitude Starting Mystery

1K views 7 replies 3 participants last post by  lovemyc280 
#1 ·
13 years ago I lived in Utah. I lived 4500 feet above sea level, but often was anywhere from 5-10k feet above sea level. Maybe twice a month, my car would not start. This always occurred when the engine was hot. It would crank, but not turn over. I always had to wait 15-20 minutes before it would turn over. The first thing I did was replace my OVP relay, but that didn't help. I never could figure out why this happened and it continued on for the 4 years I lived there.

In 2004 I moved back to Florida and drove across country. By the time I got to Texas, this never happened again. I spent 9 more years in Florida and the car started perfectly every time.

Last month I returned to the west and I'm living at 5,000 feet above sea level. The first three weeks in the valley I had no issues, but this weekend I took a trip up to the summit (8900 ft.) After a brief stop, the car would not start again. I tried a few more times and then waited. After about 20 minutes I cranked it up and it started fine.

To me, it sure seems as if the altitude is playing a role in this. What do you think it could be? It's never had trouble turning over, except when I'm at high altitude and the car is warm. Has anybody experienced something like this before?
 
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#2 ·
In later model years 1998-2000, this was commonly the crankshaft position sensor. Symptoms just like you describe, seems to be related to a hot car, random no start, and then after a short wait and nothing else, car restarts, acts normal until the next episode. For your car, this part is pretty expensive, so you might try cleaning and checking the connection first.

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#3 ·
Absolutely no clue, but just going to point out some things that I would check. First, in high altitudes, the air sucks. So my first guess is the car is starving for air at high altitudes. The converse is true in Florida. We used to race karts in Florida, and is was pretty common for us to tear up a motor or two down there because the air was so good it would cause the motor to run too lean.

Our cars tune on the fly for variations in air quality. At startup, the idle air control valve controls how much air enters the intake when butterfly is closed. It determines this based on air quality which is read by the mass air flow sensor, mass pressure sensor, air temp sensor, etc. once the computer determines the quality of the air,(and temperature of engine) it makes it's best guess and opens the idle valve if necessary, and will increase or decrease output of fuel injectors to make it run right.

So basically think of your cars computer as a mini weather station.

So the things that will screw up the weather station are if you have a bad sensor. Our cars are particularly bad about the MAF going bad, but any one in the system can cause it to revert to a known setting that will make the car run, but won't be optimized for the conditions.

The other thing that can cause your problem is if the idle control gets stuck and won't change the volume of air going in to match the injector output.

So to make a long story short, scan for codes, then make sure your iac is working. If codes say you have a bad sensor, change it and it could very well fix the problem.


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#6 ·
With my car, the symptoms progressed to a random engine shut off while driving (not good!). Would then sit in the car and wait a little while until I could start the car again doing nothing but wait. If your car starts doing this too, replace the CPS.
 
#7 ·
Idle control valve would be located in the throttle body.

Also, one of the quirks of our cars seems to be that sensors can go bad without kicking off codes. I cant tell you how many threads I've read on here of people having running issues with no codes present. I would suggest that you get codes read from both ports. There is the obd 2 port under the dash, but also a round port on right side inner fender under hood that will output a different set of codes sometimes.

And like Glenmore said, I've seen a lot of posts where guys have running issues with no codes or even a no start condition, check everything, then finally change crank or cam sensor and it fires right up. That's not to say this will work in your case, but just an fyi.
 
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