Re: O/T 350 chev Sensor question RRich
I kinda doubt you'll find any codes, scanner or A&B. If what I think it is, it's normal.
You start at low altitude, and want it to keep running fine to 7000 feet?
Uh, let me ask - how many times do your ears pop on that trip?
The ears pop to compensate for the change in Barometric pressure. Your engine can't pop it's ears.
Try something - about the time it starts to run bad, or even a little before - stop in a safe place. Turn the key off, wait 5 seconds, turn key on but don't start for 5 seconds, then start it up. It'll probably run almost as good as it did when you started up the hill.
Reason is - you don't have a separate barometric sensor. As you go higher the computer doesn't know that there's less air up there. When you first turn the key on, the ECM quick "looks" at the MAP sensor before you crank it. It stores that information as the BARO reading - then compares it to the MAP for calculations. But when going up that high eventually it's comparing AZP to old information.
Cycling the key resets the BARO reading.
I think you'll like how it runs afterwards.
Same thing going down the hill.
The older systems used a BARO sensor, but it was another thing to go wrong.
And - make sure the vacuum line to the MAP sensor is all by itself. No Teeing other things into it, small diameter - the hard plastic stuff is preferred (harder to route, but it doesn't collapse,) and as short as practical.
The hard plastic lines - use small diameter regular vac hose splices on the ends or to connect with.
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