Mild engine miss when idling?

PILOTBILL

MEMBER
2000 MERCURY VILLAGER
3.3L
V6
2WD
AUTOMATIC
84,927 MILES

Hello 2CarPros,

I have a question for you. I have the vehicle listed above (van) with A/C. Here in the past couple of months, when I stop at a stop-sign or stop-light, while sitting still the car has a mild miss, but if I have the A/C running, then there is no missing at all. I have checked the spark plug wires, spark plugs, throttle body, and air filter. Any ideas on what I should check now?

Thank you,
Bill Hewitt

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,170 POSTS

Bill,

Based on your description, my first thoughts are that there could be dirt/corrosion where the idle air control valve (IAC) mounts to the throttle body.

The Idle Air Control (IAC) valve adjusts the amount of air allowed into the engine at idle conditions and during rapid engine deceleration. This adjustment is controlled by the Powertrain Control Module (PCM). The PCM increases the duty cycle based on different inputs such as RPM, load, and others. Since the AC places a load on the engine, at idle, the PCM adjusts the amount of air entering the engine.

Here is what I recommend. Remove the IAC and inspect inside where it mounts to the throttle body. Check to see if there are any restrictions. Also, here is a link that explains how to service the IAC:

https://www.2carpros.com/articles/idle-air-control-valve-service

If you look at the attachments below, I included the directions for the removal and replacement of the IAC.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.

Images (Click to make bigger)