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post #1 of 3 (permalink) Old 05-05-08, 01:23 PM Thread Starter
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Expedition - 5.4 - erratic idle

Hi all:

Got a (new to me) Expedition 4x4, 5.4, 230,000 km, K&N Filter intake system. No other mods. In general it runs very well, but has an erratic idle and surges (at idle).

At first the vehicle was throwing lots of codes. due to the nasty shape of the K&N filter (very oily & dirty), I cleaned that up, rest, and tripped some MAF related codes. New MAF.

With all that done, now I own trip 171 & 174 codes. Plugs confirm it's been running lean for a good while before it got it. I reset the PCM (disconnected the battery for 15min). The power is a little better, but I still have the wild, erratic idle. It doesn't like to drop below 2000 rpm... after 10 sec- 20 sec, it drops to 1100, then moments later down to idle, where it surges (wha, wha, wha, wha). While driving, it doesn't kick down below 2000 rpm, so it pushes along me when coming to stops, and I have to ride the brake, or shift to neutral.

I checked all the hoses for vacuum leaks and all looks good. Replaced the PCV for the heck of it. No change in codes or idle.

So... any hints? What's left? TPS & IAC valve?

Thanks guys!

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post #2 of 3 (permalink) Old 05-08-08, 07:15 PM
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Join Date: Apr 2006
Posts: 18
Re: Expedition - 5.4 - erratic idle

Sorry brother but all THREE times I've had this problem it's been a hose. Twice I found a hose with a hole in it and it ran like a charm with duct tape. And the 3rd, a hose had come loose in the engine compartment.

No suggestions other than checking the hoses again. Your description matches EXACTLY what I experienced. As long as you are driving, no problems, if you come to a stop (like for a light or something) the engine rough idles and cuts, with all loss of power.

Good luck.

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post #3 of 3 (permalink) Old 05-22-08, 07:14 AM
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Re: Expedition - 5.4 - erratic idle

i would get the original air intake down to the maf sensor....go from there,
but yes...check your hoses. mine runs good but every once in a blue moon...it pulls away on me...like ill have to hold brake. gonna check mine myself.....have my 97 for 6 months now.4.6 i have

great forum...
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