2003 Ford Ranger engine stumble

2003 FORD RANGER
91,000 MILES • 6 CYL • 2WD • AUTOMATIC
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TOMMY R
  • MEMBER
  • 2 POSTS
On morning start up, and after sitting all day while at work, the engine stumbles, and I can hear a squealing sound, such as a loose belt would make. This only happens after the car has been sitting all night, or all day at work. If I warm it up, and gun the engine for a few minutes before driving, it does not happen. Check engine light has never come on. Had the fuel pump pressure tested, and it was OK, Recently changed plugs, wires, air/fuel filter, and throttle position sensor, and the problem still exists. Any other suggestions?
Jan 27, 2009 at 6:43 AM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Could be caused by the following:

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Jan 27, 2009 at 7:41 AM
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TOMMY R
  • MEMBER
  • 2 POSTS
Already changed plugs, and wires. Changed TPS sensor, and had the fuel pump pressure checked. I don't think it's bad gas, since I have let it run down to near empty, and have tried fuel from different places. Had the computer hooked up, and it showed no codes. I will try the fuel injectors, and then the MAF sensor.
Jan 27, 2009 at 7:57 AM
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