Idle problem, fluctuates NEED HELP
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Idle problem, fluctuates NEED HELP
I have a 91 f250 with a 351 and outo trans. I did cap rotor plugs and wires. And the truck at a stop light the idle goes up and down. With the brake on you can even feel it kind of want to lunge when the idle goes up. It doesn't die but it goes real low. the truck runs great when on the road except it shifts real real hard between 1st and 2nd Any suggestions. The check engine light also goes on and off periodically. It runs so bad at a stop light it's embarassing!
Please Help
Please Help
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
The check engine light is telling you there's a problem. Search here about pulling the codes - it's been talked to death.
Without knowing what the trouble codes are, we'd just just guessing and costing you money.
Without knowing what the trouble codes are, we'd just just guessing and costing you money.
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From: B/CS, Texas!!
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You definitely need to pull your codes, but in the mean time you might try cleaning the IAC. My '93 5.0 was doing the same thing. I cleaned the IAC with carb cleaner about a week ago and it has been idling perfectly ever since.
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The IAC is the idle air control, it's usually located on the throttle body on the right side side (looking at the motor), and it has a connector with two wires. Start the truck and get it up to temp. While it's idling, pull the connector off and see if the idle speed changes. If no change then it could be sticking or defective (try to remove and clean). With the engine off and the connector still off, take and ohmmeter and measure the resistance across the two wires inside the IAC connector, it should be between 7-13 ohms (this is normal). If it reads zero it should be replaced. Hopefully you have a meter or can borrow a buddies meter. Good Luck
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That would indicate that the IAC is working, because it controls the base idle speed. When you pull the plug the computer has no way to adjust the idle. It could still be sticking though, have you tried cleaning it yet?
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Ok now I'm screwed. I pulled the iac motor off and cleaned it really good with carb cleaner, then put it all together and the truck will not run if you take your foot off the gas. I even took the iac motor off a second time thinking that the carb cleaner froze up the moving parts and squirted a little wd40 in there and strill no change. Now I am lost. The iac motor is 76.00 and what if that isn't the problem? The truck runs great at a little higher than idle rpm, but when you take your foot of the gas the idle goes so low it almost instantly dies. Any help would be great.
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From: Fishin' my life away
howman442, I was having the same trouble, ( 93/ 302), only after I cleaned the throttle body it idles fine now. However, I can disconnect the IAC plug and it still idles just fine, should I replace?
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I'm not sure of your local auto parts place, but try to bring the IAC down there and ask if they have an ohmmeter you could use to check the resisitance. You could also try adjusting the base idle speed with the small screw on the top of the throttle body since you said it runs great with a few more RPM's, try not to adjust it higher than 1000 though.
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Triplepower, Have you had a chance to check your computer codes, or is your check engine light on? You might be going down the wrong road ( pun intended ) a defective throttle position sensor could cause a problem like yours as well.
Big Daddy, I think you are good to go. The IAC opens to let more air in to boost the idle, so if your idle speed is good I wouldn't worry about it. If it doesn't need to open, disconnecting the plug wouldn't make much or any difference.
Big Daddy, I think you are good to go. The IAC opens to let more air in to boost the idle, so if your idle speed is good I wouldn't worry about it. If it doesn't need to open, disconnecting the plug wouldn't make much or any difference.