10-08-2019, 04:22 AM
the ISC electric valve opens up as you go to 4000ft. there is less AIR at 4000ft so the valve opens more (the ISC is just and air solenoid modulated by the ECU as an electronic servo)
sure would have issues starting with so little air,so crank the engine over with say 5% (tiny) foot action on the throttle.
the MAP sensor must be working too, this sensor tells the engine the load on the engine using vacuum and at key on tells the ECU your altitude too.
EFI measures all this, and more,
400 rpm is caused by 2 things,
EGR stuck open or dead ISC. (hot engine)
seems your ISC is dead. (many are this old, and the PO previous owner HIDE THAT by , opening up the 1989/90 TV valve by screwing IN the throttle stop screw.
then later notices idle wrong later, the stop screw has no brains behind it so fails. but not hot and parked in out of gear and fiddled with.
in the old days with CARBs we went up to 10,000 feet (ski trips) and idle is too low there so we turned the screw, and also defeated the auto chock or next cold start floods the engine.
your car thinks it is CARB car.
1.3L G13 engine was but not your 1.6L (it is TBI car, and all sensors and actuators must work and yours does not)
sure would have issues starting with so little air,so crank the engine over with say 5% (tiny) foot action on the throttle.
the MAP sensor must be working too, this sensor tells the engine the load on the engine using vacuum and at key on tells the ECU your altitude too.
EFI measures all this, and more,
400 rpm is caused by 2 things,
EGR stuck open or dead ISC. (hot engine)
seems your ISC is dead. (many are this old, and the PO previous owner HIDE THAT by , opening up the 1989/90 TV valve by screwing IN the throttle stop screw.
then later notices idle wrong later, the stop screw has no brains behind it so fails. but not hot and parked in out of gear and fiddled with.
in the old days with CARBs we went up to 10,000 feet (ski trips) and idle is too low there so we turned the screw, and also defeated the auto chock or next cold start floods the engine.
your car thinks it is CARB car.
1.3L G13 engine was but not your 1.6L (it is TBI car, and all sensors and actuators must work and yours does not)
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