1999 mountaineer won't idle when first started

[mountaineer man]

I have a 1999 mountaineer with the 4.0l v6.
When first started the vehicle will not idle. It is very bad when it is cold out.
I need to keep my foot on the gas until it warms up.
What is going on?

[shorod]

Welcome to the forum!

Sounds like you have an Idle Air Control (IAC) solenoid that is failing. If you turn the A/C on, assuming the A/C works, does the engine speed drop or cause the engine to stall as well, even after the engine has warmed up? If so, that's another indicator that the IAC is an issue.

-Rod

[mountaineer man]

Thanks for the feedback Rod.
By turning the AC on does not effect the idle at all. The engine runs the same.
Could it be something else?
Is the idle air control something I can buy from an Auto parts store or is it a dealer item?

[shorod]

You can pick up the IAC from many of the auto parts stores, but if turning the A/C on does not cause a change in the idle speed, the IAC is probably working fine. That is assuming that the A/C is working fine.

If you have an EGR valve that is not closing completely at idle, that could cause what you are describing as well. A EGR not closing could be due to contamination of the valve and/or a faulty EGR vacuum regulator or DPFE sensor.

-Rod

[mountaineer man]

Is there some temperature sensor that effects the idle. Once the engine is warm it idles fine. When cold the idle is very erractic it may idle a about 1500 rpms for a couple of seconds than drop to about 600 rpms for a couple of seconds before it stops. Then I need to give it some gas to restart it.

[shorod]

Still leaning towards the IAC. But to answer your question, yes, there is a Coolant Temperature Sensor (CTS) as well as an Intake Air Temperature (IAT) sensor. The CTS will be located near the thermostat. There will probably be a Coolant Temperature Sender really close to it that will look very similar. The sender is only used for the instrument panel temp guage. The sensor is what the ECM uses to adjust air/fuel ratio, engine timing, etc.

You may also want to consider cleaning the Mass Air Flow (MAF) sensor as well. The MAF is uses a couple of very fragile sensors (hot wire and reference) though so you need to be very careful when cleaning this.

-Rod

[mountaineer man]

Rod
I changed out the IAC valve and still have the same problem. The vehicle starts but idles at about 500rpms for several seconds than it stalls. I need to give the vehicle gas to keep it running. After the vehicle is running for a couple minutes if I shut it off it starts find.

[shorod]

When the vehicle's idling at 500rpms for a short time, is it idling smoothly? If not, have you checked for vacuum leaks or to see if the EGR is closing completely? You can't check the EGR by just seeing if it will hold a vacuum. In this case, you'll want to remove the EGR and look into the valve to see if it's closing. You may even want to spray some throttle body cleaner into one passage of the valve and see if it readily flows to the other side or stays in the side you sprayed. If it readily flows, then you have a valve that isn't closing and could be your issue.

-Rod