The 1990 Ford Ranger Automatic runs fine when the gas pedal is depressed, but stalls out when it is in idle. We had exactly the same problem a few weeks ago and repaired it when we noticed one of the battery cable terminals was cracked down the side and replaced it. Upon replacement the fuel pump worked fine. We drove the truck this morning and it started to get a bit choppy upon returning home. Now it will turn over and run so long as the gas is engaged, but will stall whn the pedal is not depressed.

It is likely that the engine management system has lost its base line calibration. If the battery is weak and during the crank to start the voltage dipped low enough the Engine Control Module lost its calibration. If the pedal is depressed during the crank the TPS (Throttle position sensor) will lose the idle position for the throttle. The hunting and surging and resultant stalling is the ECM seeking out the limits and re-establishing the throttle idle plate location.

If battery is OK than running the car allowing the calibration of the vehicle to reestablish itself will correct the problem. My experience is that this happens if the gas pedal is depressed during crank with a very very low battery voltage. Always the best way is to not touch the pedal during any cranking starting procedure. Or after a battery replacement.

To accelerate the calibration process attempt to run the car ingear tring not to allow the car to stall. After afew munites the car will have reestablished its normal running calibration and you will be allset.

rebuld carberator

The two most likely causes are low fuel pressure because of a faulty fuel pump or filter, or a faulty throttle position sensor.
Is the check engine light on ?

It can be low fuel pressure issue or clogged fuel pump. Or its engine related issues,---------------

Check the help link mentioned below to troubleshoot the problem: ------

Engine stalls when gas is given?

http://technoanswers.blogspot.in/2012/01/engine-stalls-when-gas-is-given.html

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Car stalls when MAF sensor is connected?

http://technoanswers.blogspot.in/2012/01/car-stalls-when-maf-sensor-is-connected.html

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Car Engine Stalls While Driving?

http://schematicsdiagram.blogspot.com/2011/12/car-engine-stalls-while-driving.html

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Car stalls and throws white smoke from exhaust?

http://repairhelpcenter.blogspot.com/2012/01/car-stalls-and-throws-white-smoke-from.html

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Stalls And Dies At Stop Sign?

http://www.howtobyme.blogspot.com/2012/07/stalls-and-dies-at-stop-sign.html

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GMC Sonoma Stalls and idles low

http://technoanswers.blogspot.com/2012/10/gmc-sonoma-stalls-and-idles-low.html

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Nissan Pathfinder stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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1992 Chevrolet stalls and shutdown?

http://schematicsdiagram.blogspot.in/2012/04/1992-chevrolet-stalls-and-shutdown.html

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Stumbling and stalling at idle after engine rebuild?

http://schematicsdiagram.blogspot.in/2012/03/stumbling-and-stalling-at-idle-after.html

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1990 mazda 323 stalls and quit running?

http://technoanswers.blogspot.in/2012/02/1990-mazda-323-stalls-and-quit-running.html

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2000 Toyota Camry: Idling and Stalling Problem?

http://whatisbyme.blogspot.in/2012/05/2000-toyota-camry-idling-and-stalling.html

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1995 Toyota Corolla: Stalls, Sputters and Pops Through Intake Manifold?

http://whatisbyme.blogspot.in/2012/05/1995-toyota-corolla-stalls-sputters-and.html

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1999 Toyota Camry: Erratic stalling and high engine RPM at idle?

http://whatisbyme.blogspot.in/2012/05/1999-toyota-camry-erratic-stalling-and.html

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Dodge Dakota stalls, stumbles at idle. Has low fuel flow and runs hot?

http://schematicsdiagram.blogspot.in/2012/03/dodge-dakota-stallsstumbles-at-idlehas.html

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1994 Toyota 4Runner: Stalls and Stops While Driving?

http://whatisbyme.blogspot.in/2012/05/1994-toyota-4runner-stalls-and-stops.html

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1997 Toyota Camry: Erratic Idle and Intermittent engine stalling?

http://technoanswers.blogspot.in/2012/04/1997-toyota-camry-erratic-idle-and.html

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Ford Maverick: No Idle and Stalling issues?

http://schematicsdiagram.blogspot.in/2012/04/ford-maverick-no-idle-and-stalling.html

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These details will help.

Thanks.

Try depressing slightly the gas pedal to see if the engine continues to run when you put it in gear. Might have to depredd gas pedal and brake simultaniusly. if the engine continues to run, then the problem is in the idle circuit. Try decarboning the throttle body and the idle speed control.

38 lbs is not enough fuel pressure. replace the fuel pump

Did i answer you before? Anyway, try cleaning the throttle body with a little carb spray on a cloth shop towel wraped on a screwdriver.With the engine off,remove the tube to the t-body,hold the throttle alittle, and spray a couple of squirts inside.Spray some to wet the towel, and pushing it in and out gently of the t-body.becareful not to bend the plate inside or leave any towel inside.look at it with a flashlight to see if it's clean. Hope this helps

Ignition system sounds probable on vhicle when everything gets warmed up. High pitched hum could be bad tire or worse bearing.

try checking the voltage regulator
im not sure where itis exactly
but try getting that checked out

Sounds like a bad IAC (idle air control valve/sensor) that controls your idle when going from throttle to idle. If bad your idle will act crazy and can cause stalls easily. Pretty sure that's it.