Poor idle-need HELP!
 

2006 Explorer Eddie Bauer, 4.0. Bought with 75K recently.
I an not a mechanic, but get by. Car seems to run fine, except at idle. Seems to idle low, shimmy and slightly shake. It is not a normal shake. I have changed: plugs (motorcraft SP412), wires, coil pack, harmonic balancer, cleaned throttle body and cleaned MAF. PLEASE HELP!

If you unplug the MAF sensor is there any change in idle quality?

[QUOTE=hanky;94992]If you unplug the MAF sensor is there any change in idle quality?[/QUOTE

Hanky: it Immediately stalls when unplugged

Are you getting a check engine light ? Can you have the vehicle checked for any codes?

No "check engine" light. No codes. Since it stalls when the MAF is unplugged, does that mean its working properly?

Check the intake tubing between the MAF sensor and throttle body for a hole or possible air leak.
If unmeasured air is getting into the engine without being measured by the MAF sensor the system will compensate for that addl air by adding addl fuel.
The system is designed to substitute values to allow the engine to keep running when the MAF is removed from the system, but instead it is stalling.
A scan tool is used to look at fuel trims to confirm if this is happening. You should have a C/E lite when you disconnected the MAF plug, did this happen ?

Hanky, thank you for your efforts/replies. I will check for a hole/airleak where you mention. What do you mean when you say C/E light?

That's how a lazy guy like me says, "check engine light".

Lazy. I get it.


C/E light comes on only when car stalls after unplugging the MAF.
I still have to look for the possible leak you mention. Do you know what the idle should be when in park? How about when in drive?

Idle speed is no longer adjustable because it is controlled by the computer. Whenever any addl load is placed on the engine various inputs keep the computer informed and it adjusts idle speed automatically. The manual lever position switch on the trans lets the computer know when it is placed in any gear so it can keep idle speed constant.