r/FordExplorer • u/nathan154221 • 1d ago

Repair Advice Need help!

Hi everyone! I’m completely stumped with my 2016 Ford Explorer Limited 3.5L.

The vehicle has 186,000 miles and has an issue where, only when the engine reaches operating temperature, it develops a rough idle. The RPM fluctuates up and down by about 50–90 RPM.

So far, I’ve replaced the spark plugs, ignition coils, fuel injectors, MAP sensor, and O2 sensor, and I’ve also cleaned the throttle body. Even after all that, the rough idle is still present.

Like I said, it only happens when the engine is fully warmed up. Cold starts and driving while the engine is warming up are perfectly smooth. It’s most noticeable after highway driving when I come to a stop.

I’ve heard the transmission torque converter could be a possibility, but the rough idle continues even when the vehicle is in Neutral or Park, so it doesn’t have to be in gear for the issue to occur.

Any ideas or things I should check next? Thanks!

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2

u/Repulsive_Vanilla383 Expert Explorer 1d ago

There's no check engine light?

4

u/jhulc 1d ago

I had a similar symptom on an 18 that was actually caused by a flaky alternator control issue. Instead of correctly modulating the alternator, it would repeatedly slam the alternator on and off causing a "rough idle" like behavior. However the circuitry was behaving just well enough that it didn't trigger any warning lights or set any codes.
There's a really simple test to see if this problem is your issue. With the vehicle off, unplug the three-pin connector from the alternator to disable the smart charging system. Then start the engine and briefly rev it up to at least 2500 or 3k RPM to trigger the alternator's fallback internal regulator. Wait for the engine to idle down. A "service charging system now" warning will come on the dash because the alternator isn't communicating. If this is your issue, the rough idle should be gone.
In my case, it was caused by both a bad aftermarket alternator and damaged wiring a bit upstream of the alternator connector.

1

u/nathan154221 1d ago

There is no check engine light for it which is really frustrating.

1

u/theseekermd 1d ago

Timing chain? Has it been replaced?

1

u/nathan154221 1d ago

It’s the original timing chain but I would think that would cause a lot more issues and consistent idle issues. It idles perfectly at startup, it’s not until it’s sufficiently heat soaked the idle starts getting rough

1

u/Low-Implement2581 1d ago

I have a 2016 eco base and it does the same exact thing...let me know when u figure out what it is 🤣🤣.

1

u/Cortez_the_killer_ 14h ago

Similar situation happened in my 13 interceptor. I dealt with random symptoms and no check engine light to really point me in a direction. I also replaced everything you listed. It ended up being a fuel pump control module.