99 Ford Ranger wont stay idle and cuts off when I let off of the gas - Ranger-Forums - The Ultimate Ford Ranger Resource

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Old 01-10-2015
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Location: forest park, GA
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99 Ford Ranger wont stay idle and cuts off when I let off of the gas

Hello Ford Ranger enthusiasts, I am in need of some serious help right now I have been working on a 99 ford ranger 2.5L engine that has 163,666 miles on it. I am having issues with the car staying idle once I turn it on. it starts and then starts shaking real bad then cuts off. when I drive it drives fine but when I take my foot off of the gas that is when it just shuts off. It has new spark plugs and wires, new oil filter, new belts and water pump, new clutch sensor a different but not new IAC Valve that I just cleaned along with the throttle body it has a different MAF sensor but I am still having issues. I do not have money to pay a mechanic that is why I am doing this myself and need any suggestions to why the ranger is cutting off of me. thank you so much
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Old 01-10-2015
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When you start a fuel injected engine cold the idle should go up to 1,600 then drop to about 1,200rpms
It should then slowly drop to about 750rpms diuring 8 minute warm up.
That's the computer operating the IAC valve.

Computer opens IAC Valve all the way on startup, thats the 1,600
It then checks the engine temp using ECT sensor, if cold that's the 1,200
As Engine warms up per ECT sensor computer will lower the idle until "warm idle" target is set.

So try starting engine cold, DO NOT touch the gas pedal.

If engine won't start you have other issues

I would guess a vacuum leak since that is a common issue.
Second would be EGR valve stuck open, EGR valve should only be open AFTER warm up, and then only when engine is under a load, accelerating or going uphill.

Vacuum leak and EGR issue would effect idle the most, engine could seem to run OK while at higher RPMs
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