1999 Ford Expedition dying all the time

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I am having trouble with my 1999 Ford Expedition dying all the time now. Happens both when it is cold and warm. Mostly when the engine is cold and I am backing down the driveway. I have
85K on it, the 4.6L and it is maintained by Helfman Ford. Last year they replaced the spack plug wires and spark plugs due to "arcing".
Tonight it is 35 F outside, it died several times when I started it to go home from work. Then it died in the driveway into the garage (after a 5 mile drive, a first).
The last tank I ran in it was premium. I have learned not to go to a certain shell gas station since it's regular causes many of the same symptoms.
I welcome all opinions and conjectures.
Thanks, Lynn
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Lynn wrote:

From the earlier "Throttle Position Sensor thread:
Mortimer Schnerd RN wrote:
I got in my 2000 Taurus SE Friday for the drive back from the coast (outside temp around 35F and the car didn't want to start. It cranked just fine but acted like it wasn't getting any fuel. Once I started keeping my foot on the gas, it started but stalled if I let it just idle. It seemed to want to idle between 3-500 rpm; much slower than its normal 1100 cold and 700 warm. I just kept giving it gas while I changed gears from park to drive. It ran smoothly in cruise the whole way but continued to stall if I stopped at a light without keeping my foot on the gas. Finally, it seemed to start idling correctly after about 4 hours worth of mostly highway driving.
I'm curious what the problem is. Obviously, I've got to get it fixed but it's running OK right now. I don't expect that to last though...
Ideas?
Frank wrote:

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Lynn wrote:

This vehicle was designed for reg. unleaded, 87 octane. Premium can cause driveability problems, reduced economy, higher emissions, and a smaller bank balance.
Rob
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your idle air controller is bad premium fuel is ok to use, and a good idea to run a tank full every now and then. I only run premium, and get 5-6 miles per gallon better mileage over 87 octane with my 4.6.

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tom wrote:

It's your imagination... hard to believe the fuel means the difference between 13 mpg & 18 mpg...
Rob
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wrote:

I find that hard to believe. Been around and worked on cars for over 50 years and this is the first I heard of this.

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if it is all in my head, how is it that when I use reg I get 12-13 mpg, but with prem, I get 17-18 mpg??the same is true with my 99 crown vic. with reg gas it gets 19-22 mpg, with premium, it gets 25-27mpg. this all highway miles, cruise set at 65 mph.my 65 falcon with 289 4bbl C/4 trans gets 18- 20 on reg, and 22-25 on prem "pick one" <try again!> wrote in message

same
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You then must be that one exception when it come to things like science and physics. Every thing you touch must turn to gold as well?

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but
reg
20
You need to make more careful measurements and do the calculations over multiple tankfuls (at least three, five is better). I have compared premium and regular fuels for multiple vehicles (two Expeditions, a Mustang, an F150, and a Saturn). Not one got a statistically significant increase in fuel economy when using premium fuel. I was sure the Mustang would not, since it does not have a knock sensor, and therefore has no way to adjust for changes in gas quality. I did expect a slight increase in the case of the Expeditions. I was so disappointed that I actually ran premium for over 20,000 miles in the 1997 to try and detect a difference. I even disconnected the battery in an attempt to force the PCM to relearn the setting. None of this made any difference. At least in 1997, Ford did claim that you would get slightly more power if you ran premium. The PCM used by Expeditions is able to adjust engine parameters (mostly ignition timing) if premium fuel is used. This adjustment when premium fuel is used might (should) result in slightly better fuel economy. However I never could detect it despite extensive efforts to do so. Modern regular and premium fuel contain essentially the same energy content per gallon, so there is no reason to expect more than a minimal increase in fuel economy when changing fuel. Any increase would solely be related to improving the efficiency of the engine. Unless there is something seriously wrong with your engine, a 50% increase in fuel economy is simply not believable. I can assure you that if such an increase was possible Ford would require the use of premium fuel (and be completely justifiable in doing so). Ford struggles to meet CAFE restrictions. A 20% to 50% in fuel economy would be godsend.
If you still believe that you get 50% better fuel economy in your Expedition when running premium, why don't you think Ford requires the use of premium fuel?
Regards,
Ed White
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and
I agree that it sounds like a bad IAC motor.
I think you need to make more careful calculations with regards to fuel economy. Unless there is something seriously wrong with your vehicle, there is no way you are getting 5 to 6 mpg better mileage just by using premium. I have owned two Expeditions. I ran extensive comparisons between regular and unleaded fuel with both and never got any measurable increase in fuel economy by using premium gas (or synthetic oil for that matter). In theory, you might get slightly better fuel economy since the PCM in the Expedition will readjust the timing when you use premium. Ford claimed an extra 5 to 10 HP and up to one half mile per gallon fuel economy improvement with the use of premium. A 5 miles per gallon increase is x-files territory.
Regards,
Ed White
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I run a tank of premium gasoline every five to ten tanks or so. Premium gasoline has more detergent in it than regular gasoline:
http://www.chicagotribune.com/classified/automotive/columnists/chi-0412190322dec19,0,823307.column
http://www.babcox.com/editorial/us/us10325.htm
Lynn
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Your links say nothing of the sort. Try reading them again.

http://www.chicagotribune.com/classified/automotive/columnists/chi-0412190322dec19,0,823307.column
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Lynn wrote:

snip / / / /
Getting back to your original question, did you try R & R and cleaning of the Idle Air Control Valve?
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Not yet. That will give me something to do for the weekend after the festivities.
I just checked on the price of a new IACV. $130 from my dealer's parts department !
Lynn
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Lynn wrote:

I cleaned mine about three months ago. Easy. Still working fine. Near as I can tell there's a shaft that gets a little dirty and starts sticking. The electrical part works fine once the shaft is cleaned. Two small bolts and a couple easy hoses. The other poster said he paid 268.00 to the dealer for the fix. After cleaning hit it one time lightly with wd-40.
Frank
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Cool ! I will try that first.
I did find a cheaper place ($97.49) for the IACV. http://www.parts.com/partlocator/index.cfm?action=getLocatorKeySearch&siteid !3787&chapter=DP2120&catalogid=1&year99&make&model=Expedition
Lynn
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Lynn wrote:

http://www.parts.com/partlocator/index.cfm?action=getLocatorKeySearch&siteid !3787&chapter=DP2120&catalogid=1&year99&make&model=Expedition
Cleaning an IAC is a very cheap alternative to replacement,But.. IMHE it is a hit or miss fix. I always clean them first. I've cleaned some and it didn't work, or only lasted a short time before sticking again. I've also cleaned some that were trouble free for years. Just be aware that it may not work and you'll have to spend the bucks.             Tom
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I replaced the Idle Air Control Valve (IACV) and all is good !
Thanks, Lynn McGuire
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I only paid $55 for mine at napa

of the Idle Air Control Valve?

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