Engine stalls at idle, why?

Hi,

This could be a few different things. First, an engine vacuum leak can cause a rough idle or even stalling. Also, an idle air control valve (IAC) is responsible for maintaining the engine's idle speed. That can be failing and not set a code.

When you turn the A/C on and off, do you hear the idle speed up to compensate for the added load of the compressor? Also, have you looked for any vacuum leaks? Here is a link that explains how it is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

As far as the IAC, I need to know the correct engine size. The 5.4L was not an option on the Explorer. However, here are a couple links you may find of interest. One explains how to service the IAC and the other shows in general how one is replaced.

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

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Let me know if this helps and the correct engine size so I can look further into the issue.

Take care,
Joe

You said this is an Explorer with a 5.4L. I assume you meant Expedition or did you get the engine wrong? I attached the info on the IAC for the 5.4L which is the most common cause of this.

I attached a guide on how to clean this but it is not that expensive so you may want to just replace it.

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

Let's run through this and let us know what happens. Thanks

Taking a vacuum line loose (letting the intake suck in air) may have bypassed a "going bad" or "dirty IAC" (fix the issue, put the line back on.)

The "IAC" regulates air to idle the modern engine. Its a bypass over the "closed throttle plate" and the computer moves a plunger within it to regulate just the right amount of air flow thru it

This may not be the answer, but you can EZily rule it out! This will sorta guide you to what you have to do, it is really EZ to do!

My wifes' is on the top and has 2 bolts. Our Escape would idle low, then it got to point it would die when you stopped. Revving + holding brake was only way to keep it running.

Took it to fellow R/C airplane pilot, he doubles as a S.C. State HWY DEPT mechanic.(I still live in the carburetor age!).

When I got to his house, he was repairing a tractor. Told him my sob story. Escape was still barely running.

I raised the hood. He said, (and I quote)."It could be the IDLE AIR CONTROL (IAC)", as he pointed to it, and emphasized it with a sharp rap using the wrench in his hand.

It straightened right up, and ran darn good!

That was a 15/16 Craftsman wrench, box end, kinda a medium rap.

We removed and cleaned it, it may have gone on being Fine, for a lot longer.

Since it was my wife's, I took no chances, with my Well-Being.

YES, I visited parts store and replaced it, figgered it had 100,000 miles on it, and constantly was a moving part, replacement of this component, was just preventative maintenance in my eyes.

Hope this helps. Hope I am dead on! Cleaning would be FREE (can of throttle body cleaner), and at least Maybe eliminate this factor out of the equation. You can go on and replace it later, if you have the same feelings about it as I did. It is not really expensive. Yours will look very similar to ours

Please let me know how this goes.

The Medic

Have you check for fuel pressure yet?

Very possible. Unhook the vacuum booster and plug all lines. Try it to see if it stalls again, if not the booster or check valve may be bad

That injector will cause a lot of problems. According to your codes you need to get that injector replaced before moving any futher.

Does the check engine light come on while the engine is still running or after it has stalled?

That's normal.

You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.

You may have a bad IAC ( idle air control) but try cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.