4.6 idle problems
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Joined: Jul 2003
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From: houston
4.6 idle problems
i posted this above in the 1997-2003 section, i just really need help. thanks
i have a 1997 f150 with a 4.6 and about 190K miles on it. the problem is, is that when i come to a stop and the truck is idleing it is only at 490- 510 rpms, and sometimes i will stop and it will drop down to 200-300 then jump back up to 500, when it idles at 490-510 it shakes, not terably but it does have a "rithim" to it. also this only happens when the truck has fully heated up, when the temp gauge says anything lower than it's usual running temp. when in park and neutral, and fully heated it's rpms are at about 550.
i thought it was the IAC and so a couple months ago i replaced the IAC and i pretty much solved the problem, the rpms still weren't at 700 but were alot better and never droped down, and just recently i changed the oil and started running it on premium it sarted doing it again.
could running it on premium be causing the problem? should i replace the IAC again? could it be the TPS? or some other problem?
Any kind of help would be greatly appreciated. thank you
i have a 1997 f150 with a 4.6 and about 190K miles on it. the problem is, is that when i come to a stop and the truck is idleing it is only at 490- 510 rpms, and sometimes i will stop and it will drop down to 200-300 then jump back up to 500, when it idles at 490-510 it shakes, not terably but it does have a "rithim" to it. also this only happens when the truck has fully heated up, when the temp gauge says anything lower than it's usual running temp. when in park and neutral, and fully heated it's rpms are at about 550.
i thought it was the IAC and so a couple months ago i replaced the IAC and i pretty much solved the problem, the rpms still weren't at 700 but were alot better and never droped down, and just recently i changed the oil and started running it on premium it sarted doing it again.
could running it on premium be causing the problem? should i replace the IAC again? could it be the TPS? or some other problem?
Any kind of help would be greatly appreciated. thank you
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Freshman User
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From: houston
p.s i looked undernieth my hood, to see if anything looked wrong and i noticed that a couple of my spark plug wires a resting on the head covers, somone told me your wires should not toch any hot part of your engine, could this be it?
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Joined: Oct 2003
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From: West Virginia
It could be so many things,Do you have a check light on?Could be a vacume leak also.You can spray carb cleaner around the motor like the Intake are and if there is an external vacume leak it should raise the RPM's up whe u hit it.
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Stoner, I had a similar problem with my 98 F150, 4.6L. I can only tell you in my unskilled "backyard mechanic" terms. I pulled in my garage and left my truck running. Popped the hood and took a pair of pliers and tapped on some of the vacuum switches. Just to the right, and behind the thottle body cover is a valve with a plug attached. When I tapped on it the idle leveled out so I removed it and sprayed some carb cleaner in it and it's been fine ever since. It's a cartridge about 2 inches long and inside is a needle valve that was gummed up.
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From: Philly
Originally posted by plainoleboy
Stoner, I had a similar problem with my 98 F150, 4.6L. I can only tell you in my unskilled "backyard mechanic" terms. I pulled in my garage and left my truck running. Popped the hood and took a pair of pliers and tapped on some of the vacuum switches. Just to the right, and behind the thottle body cover is a valve with a plug attached. When I tapped on it the idle leveled out so I removed it and sprayed some carb cleaner in it and it's been fine ever since. It's a cartridge about 2 inches long and inside is a needle valve that was gummed up.
Stoner, I had a similar problem with my 98 F150, 4.6L. I can only tell you in my unskilled "backyard mechanic" terms. I pulled in my garage and left my truck running. Popped the hood and took a pair of pliers and tapped on some of the vacuum switches. Just to the right, and behind the thottle body cover is a valve with a plug attached. When I tapped on it the idle leveled out so I removed it and sprayed some carb cleaner in it and it's been fine ever since. It's a cartridge about 2 inches long and inside is a needle valve that was gummed up.
I THINK that was your IAC you were tapping. It has been said, that they get all carboned up and begin to malfunction. For our Turbo cars, we have had great success just removing them and cleaning em real good with a toothbrush and carb cleaner. Once accomplished, we usually get alot more life out of em, before they actually go bad and need to be replaced. Not sure how much one costs for a ford, but for our 3/S cars, they are over $200.00, so it's WELL worth trying to clean it first...
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