4.0 stalling | Ford Explorer Forums - Serious Explorations

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4.0 stalling


Active Member
January 20, 2004
Reaction score
City, State
Thornton, CO
Year, Model & Trim Level
1991 XLT
Anyone had this problem? I was driving last night when all of a sudden, the truck would stall and hesitate when I would push the gas pedal. If I just touched the gas it would run fine, but give it anymore than just a touch, it would bog down when driving and stall when starting from a stop. Any suggestions?

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is the cel light on. check the fuel pressure regulator

I got a fuel pressure tester today and got these readings. I turn the key to on and the book says that there should be 35-45 psi. There is none. I start the truck and the pressure goes to 40psi. I turn the truck off but the key on and the pressure slowly drops to 0. Is the the pressure regulator?

Could be the regulator. could also be the check valve in the fuel pump (though a bad check valve by itself shouldn't cause the kind of driveability symptoms you're experiencing). Or a faulty/leaky fuel injector. Or a leak in the fuel lines from the pump to the fuel rail. Or a leak in the fuel rail.


dude I'm having the same frecken problem and the dealer is not able to find the problem....Ive taken it twice and Nothing. If you find the answer please let me know

I am going to get a pressure regulator today. After that I will start checking the lines. I will also replace the o-rings on the injectors. I will post results.

Ok problem fixed. I replaced the fuel pressure regulator but the problem was the coolant temp sensor(not the sending unit-2 different parts). That is why I had problems once it warmed up. Hope this helps anyone else.

Check the pressure again and see if it holds now. Some fuel pressure regulators will wear the seat only on one side because of an offset spring. This will cause the leakdown. In some cases the valve will hang open and cause stalling. I am a little leary when pressures are read because the schraeder valve at the test port may not fully open causing false readings. I have to remove it to get any reading. Because the regulators are high bypass, 80%, leaking regulators continue to work. As long as it isn't the bellows. I don't think replacing it was a waste of $$$. You should disconnect the battery to reset the computer. Mine had poor performance and didn't learn after 200 miles. Resetting the computer fixed that.

Thanks Opera. I checked the pressure and it was the exact same after replacing the pressure regulator. It ran better after replacement but the pressure would still drop after running but pressure stays at 40psi while running. I still had the stalling so I went to Autozone to try a fuel filter. The guy there said to try the temp sensor due to the symptoms of running fine while cold but stall when heated up.
After replacing the sensor the truck runs great with no stalling. This makes sense because all summer the truck would overheat. I installed a Sunpro gauge, new thermostat, new water pump, electric fan, and had the system flushed. It continued to overheat so I installed a larger radiator from a '87 ford Country Squire that had a 302 and installed dual 12" fans.(luckily the radiator was brand new) This stopped the overheating problem because it holds an extra gallon of coolant but all along it was probably this sensor.
Either way it runs great now and at least I have a completely new cooling system