- Joined
- Jun 2, 2012
- Messages
- 25,363
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- Location
- canada
- Vehicle Year
- 1994
- Make / Model
- Ford
- Transmission
- Manual
Start the engine, foot OFF the brake, run it for say 30 seconds and shut it off
Press brake pedal down, and let it up, should get 2 or 3 "vacuum assist" presses until pedal gets hard to press
The size of the booster is so a driver can get 2 or 3 power assist braking pushes to get off the road safely after a stall, just FYI on why the booster is so big, lol
Computer has an "idle bump" it uses when transmission is shifted OUT of Park or Neutral, same if you have AC and turn it on
Computer should bump up idle about 75-100RPMs after shifting into gear
It uses IAC Valve to do that
Is it a Motorcraft IAC Valve?
3rd party IAC Valves can work fine then not work fine, then work fine, then..........ect
Its because they are usually solenoid/stepper type "motors"
Rangers need solenoid type only, which is Motorcraft or Hitachi brands
Idle bump is done when Neutral switch no longer shows neutral(ground), on pin 30 of computer
Try replacing PCV Valve, its a controlled vacuum leak, when it gets dirty it can stick so changes vacuum draw, usually computer sees that(drop in RPMs, and can respond fast enough, but not always
And they are cheap and should be changed every 3 oil changes anyway, which no one does, lol
And you can re-adjust the anti-diesel screw to keep idle above 650 or so
After engine is fully warmed up and idling, unplug the IAC valves 2 wire connector
Idle should drop, this is good, no vacuum leaks, lol
But if engine stalls then you can adjust the anti-diesel screw, it looks like an idle screw on throttle linkage, but fuel injection can't use an idle screw, lol
Any way turn it clock wise a bit to increase idle RPMs and restart engine if it stalled, IAC Valve still unplugged
650 RPM is a low but steady idle
Plug back in IAC Valve and RPMs should go up to 750
Unplug it again
You can adjust it so idle is higher but lower than IAC Valve when its plugged in
Then unplug IAC again and shift trans into drive and see if it stalls
That should get you by until problem is found
Press brake pedal down, and let it up, should get 2 or 3 "vacuum assist" presses until pedal gets hard to press
The size of the booster is so a driver can get 2 or 3 power assist braking pushes to get off the road safely after a stall, just FYI on why the booster is so big, lol
Computer has an "idle bump" it uses when transmission is shifted OUT of Park or Neutral, same if you have AC and turn it on
Computer should bump up idle about 75-100RPMs after shifting into gear
It uses IAC Valve to do that
Is it a Motorcraft IAC Valve?
3rd party IAC Valves can work fine then not work fine, then work fine, then..........ect
Its because they are usually solenoid/stepper type "motors"
Rangers need solenoid type only, which is Motorcraft or Hitachi brands
Idle bump is done when Neutral switch no longer shows neutral(ground), on pin 30 of computer
Try replacing PCV Valve, its a controlled vacuum leak, when it gets dirty it can stick so changes vacuum draw, usually computer sees that(drop in RPMs, and can respond fast enough, but not always
And they are cheap and should be changed every 3 oil changes anyway, which no one does, lol
And you can re-adjust the anti-diesel screw to keep idle above 650 or so
After engine is fully warmed up and idling, unplug the IAC valves 2 wire connector
Idle should drop, this is good, no vacuum leaks, lol
But if engine stalls then you can adjust the anti-diesel screw, it looks like an idle screw on throttle linkage, but fuel injection can't use an idle screw, lol
Any way turn it clock wise a bit to increase idle RPMs and restart engine if it stalled, IAC Valve still unplugged
650 RPM is a low but steady idle
Plug back in IAC Valve and RPMs should go up to 750
Unplug it again
You can adjust it so idle is higher but lower than IAC Valve when its plugged in
Then unplug IAC again and shift trans into drive and see if it stalls
That should get you by until problem is found
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