2006 with low rpm idle....what is it?

[rwinsouthla]

Hey y'all,

I have a 2006 5.4L Expedition with 160,000 miles. It starts fine and runs fine while cruising at any speed. But when I slow down for a light or stop sign, it goes to crazy low idle speeds and sometimes dies, hot/cold/rain/shine. Start it back up and in park, no issues but put it in gear and down the rpm goes. What can it be?

Thanks in advance!

Ray W in South La.

 

[stamp11127]

Is the check engine light on? If so, you should have the codes read at your local autoparts store if they offer the service.

 

[rwinsouthla]

No Mr Stamp. No check engine light comes on so I can't get codes.

 

[stamp11127]

A couple things come to mind but it is better to attack this the old school way - back to basics. Since the cel isn't on the ecm is saying the engine is still within set operating parameters. The first thing would be to check what operating state it is in.

1) Make sure the light for the CEL is working - turn key to run but don't start it. The light should come on.
2) When was the last tune up - spark plugs and air / fuel filters?
3) Has the MAF, throttle body and egr ports been cleaned?
4) May want to have the codes read, looking for historic codes.

You can think of this as being the checkup the doc gives you when you go in for something. They are looking for something that isn't within the normal range.

 

[rwinsouthla]

What's MAF?

CEL works bc it threw a #2 coil pack a few months back, worked then and continues to come on when I crank it or it dies. Spark plugs changed at 125k. All coil packs changed around September. Fuel filter too.

Will clean the TB next weekend.

 

[SuitCat]

My 04 expy did the same thing, started great and would always almost die if not die at a stoplight, we replaced the terminals for the battery and I never had another problem with it!


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[Lithiatwats]

MAF is mass air flow sensor. Critical for your correct running in terms of fuel/air ratios based on ambient conditions etc. Cleaning your throttle body will help, with 160000 miles, when did you last do basic maintenance such as filters etc? An ounce of prevention is worth a pound of cure! Battery terminals cleaned and slathered with Vaseline wont hurt either