86 idle problems and noise
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86 idle problems and noise
I have a 1986 F150 with 302 auto and 4 wheel drive.My problem is when you put the truck in gear the idle raises before it goes in gear,also when you come to a stop in drive the idle goes low and the engine seems to want to stall.The rpms drop before they raise and sometimes the truck stalls.It is driving me crazy.I have replaced the idle air control,plenum gasket,and throttle position sensor and had no luck.There is also a noise that sounds sort of like a lifter tap but only does it at low rpm when my foot is on the gas,if I let off the gas the noise goes away.I am looking for any help or suggestions and they would be greatly appreciated.I am at wits end and almost to the point I am ready to get rid of this truck.Please help.Thanks in advance.
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Hey liljase I have an 86 F150 as well and mine does the same thing. I tried a tune up changing plugs, distributor cap and rotor, changed wires and the fuel filter, and air filter. Guess what?? Still does it and I took it to 2 mechanics and one of them told me it was coming up with an emissions code. Try your oxygen sensor? Maybe a vacuum line? I don't know I have been trying to track it down if you find out whats wrong please let me know.
Ian
Ian
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I also tried the tune-up and still nothing.I was thinking about taking the spring off the throttle stop screw on the throttle body and adjusting it to maybe hold the rpms up a couple hundred.If I hold my foot on the brake and give it a little gas with the other it works fine.Is that the same as yours?I dont know what else to do.Please let me know if you come up with any other ideas.Thanks.
Jason
Jason
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i think i may have an answer, if both u guys have mods of any sorth on ur engines its problay the IAC sensor, i just bought a iac spacer plate its suposed to make a smoother idle and run better if u have mods. Ill let u guys know when i run my truck with it if it helps.
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Thanks for the reply F250r but my truck is completely stock.I just put on a new IAC sensor but no luck.I am curious about the spacer plate if that smoothes out the idle I will try it anyway.I dont know anything else that might cause this.Thanks again,
Jason
Jason
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From: GANS
Sounds like your motor is pinging, from your description. Try 93-94 octane, and see if it goes away. If it does, your timing might be off. Or, your truck could be running lean.
Another thing to do is, put a timing light on the truck and see if it is bouncing around a lot. That would indicate a worn timing / chain and gears, which is pretty common for high mileage 302s..
Another thing to do is, put a timing light on the truck and see if it is bouncing around a lot. That would indicate a worn timing / chain and gears, which is pretty common for high mileage 302s..
