Adjusting the Idle Speed

It doesn't appear to be a performance modification, but it is. After some of the modifications that I have done, the idle speed lowered. It caused a bogging when first accelerating. Too low an idle speed will cause bogging! I thought that it may result in better fuel economy if your idle speed is lower. I felt that the idle speed was set a little bit too high at 800 rpm and tried the following procedure to reduce it. Instead it created the bogging.

Here's a procedure to adjust the idle speed on a Ford 2.3L computer controlled engine:

NOTE: Engine should be at normal operating temperature before performing this procedure!

  1. Turn off all accessories and disconnect the battery for 5 minutes.
  2. Reconnect battery. Disconnect the Idle Speed Control (ISC) solenoid located just behind the throttle body on the drivers side of the upper intake plenum.
  3. With the truck in NEUTRAL, run the engine at 2500 rpm for 30 seconds.
  4. Let the engine idle for 2 minutes.
  5. Put the truck in PARK (or NEUTRAL if manual trans.) and adjust the idle speed stop screw until the idle is at 700rpm.
  6. Turn engine off and let sit for 2 minutes then repeat steps 1-5 once.
  7. Disconnect battery for 5 minutes then reconnect.
  8. Reconnect the Idle Speed Control (ISC) solenoid.
  9. Run the engine at idle for 2 minutes.
  10. Quickly depress the accelerator pedal to the floor and release it immediately, allowing the engine to return to idle.
  11. Lightly depress and release the accelerator allowing the engine to return to idle.

After carefully following the above steps, the engine should now have reset its base idle to factory specifications. The idle should now be smooth and at approximately 700rpm at operating temperature. If this procedure does not correct the fast idle condition, carefully check for vacuum leaks at the throttle body flange gasket and at the intake snorkel to throttle body interface. If no vacuum leaks are detected and the condition still exists, a condition that is unrelated to the mechanical throttle body assembly exists and must be diagnosed and repaired.

NOTE: When I changed to 19 lb/hr fuel injectors, the idle speed dropped to 650 rpm. I thought that was a good thing but started to have acceleration problems that I thought were related to the new injectors. The engine would bog on acceleration big time if you floored it. I also was getting the engine light turning on and off as I drove. The engine code was 179 - rich mixture on partial throttle. It ended up being too low an idle speed. You adjust the idlespeed to 800 rpm and my bogging problems went away.

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Copyright February 2011 Eugene Blanchard