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Discussion Starter · #1 ·
I have a 1986 EFI 5.0 HO which has a rough surging idle. When the car was given to me i replaced the ignition switch because the car would not stay on unless i pressed on the gas. Then i replaced the spark plugs and the coil and it ran a little better. But the idle speed drops really low every few minutes and idles rough. However when the car warms up it idles a little smoother. Then when i turn on the air conditioning the idle speed stops surging and it idles smoother. I cant seem to figure out the problem. My spark plug wires seem fine but my distributor cap wiggles side to side.
 

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What you would check would be (and in this order):

spark plugs
coil
secondary wires
cap/rotor
timing
IAC valve
electrical and vacuum connections
fuel regulator
injectors
fuel rail (leaks)
fuel lines (leaks)
 

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Discussion Starter · #3 ·
My spark plugs and the coil are new. My cap wiggles which does not seem normal. So i should probably change the cap, rotor, and the wires. I recently cleaned the IAC valve but the spring could be bad. Thanks for the help. I will go down the list until it fixes the problem.
 

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Discussion Starter · #4 ·
What you would check would be (and in this order):

spark plugs
coil
secondary wires
cap/rotor
timing
IAC valve
electrical and vacuum connections
fuel regulator
injectors
fuel rail (leaks)
fuel lines (leaks)
I started working my way down the list and i have replaced the spark plugs, coil, wires, cap and rotor. I also cleaned the IAC valve with Mass Air Sensor cleaner. It idles much smoother now but when it is cold the idle drops down really low and shoots back up to the normal 700 rpms. Could it be a bad IAC valve? But once the cars warms up it idles normally.
 

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Odd thing is mine does the same thing, there's no such thing as a smooth cold start for me, I have to babysit it for a minute or two until it smooths out. When it was stock, I could reach through the window and start it, and go back in the house, and have no problem. I do that now, it'll die before I get 10 feet away from it.
 

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Discussion Starter · #6 ·
Odd thing is mine does the same thing, there's no such thing as a smooth cold start for me, I have to babysit it for a minute or two until it smooths out. When it was stock, I could reach through the window and start it, and go back in the house, and have no problem. I do that now, it'll die before I get 10 feet away from it.
What is funny is mine is completely stock and it still does that. I have no mods on it so you think it would not have a problem like that.
 

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Discussion Starter · #7 ·
Yesterday I took apart the throttle body, IAC valve, TPS sensor, and the EGR valve and gave them a good cleaning with MASS air flow sensor cleaner and throttle body cleaner. Then i reassembled everything and it idled smoothly. I think that was the solution to my problem.
 
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