1990 4.0 - Ranger-Forums - The Ultimate Ford Ranger Resource

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Old 02-29-2016
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Join Date: Apr 2011
Location: Athol Id.
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1990 4.0

My 1990 4.0 just won,t idle smooth,in fact at times I need to shift to neutral . I posted this before and I don,t like buying parts shotgun style. This does it sometines when its cold and then it may do it when warm? Help out a old mAN. [email protected] thanks
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Old 02-29-2016
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Location: Vancouver, BC
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IAC(idle air control) Valve is how computer sets warm and cold idle RPMs.
It should be cleaned every 5 years or so.
Just 2 bolts.

read here for details: How to: IAC valve cleaning thread (w/pics) - Ford Explorer and Ranger Forums "Serious Explorations"

4.0l OHV engines eat most brands of spark plugs, Motorcraft seem to last the longest, then Autolite.
Never use single platinum spark plugs on distributorless Fords, regular or double platinum only, single is a waste of money.

Worn out spark plugs cause rough idles.

My '94 spark plug wires lasted 18 years, but they did eventually start to cause misfires, poor idle.
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