throttle body
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Junior User
Joined: Jun 2003
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From: GrandRapids MI
throttle body
hey guys there is a 5/16 set screw on the top of my throttle body. it was backed olmost all the way out when i turn it down it opens up the throttle. were is the proper setting for this. if you need to set this at so many rpm at idle then i need to know if there is a way to check rpm with a volt ohm meter.... i have no tach.
Posting Guru
Joined: Jun 2002
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From: redding U.S.A.
throttle body
a volt meter will just start bouncing back and forth like crazy.
If you can count how many times it flicks in a minute...
you can pick up a tach for about $25 probably... its not gunna be good, but it'll work fine for diagnosis like that.
If you can count how many times it flicks in a minute...
you can pick up a tach for about $25 probably... its not gunna be good, but it'll work fine for diagnosis like that.
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From: Broken Arrow, OK
throttle body
Some timing lights have a tach built into them. If you get one of those you get two tools for the price of one. Sorta.
Actually, if you unplug the IAC and let the engine idle you can get pretty close to the proper adjustment by setting the screw to a position that will just barely allow the engine to run.
Actually, if you unplug the IAC and let the engine idle you can get pretty close to the proper adjustment by setting the screw to a position that will just barely allow the engine to run.
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Junior User
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From: GrandRapids MI
throttle body
thanks for the info guys silver streak i unplugged the iac and backed the screw all the way out it still ran. what rpm are the 4.9s supposed to idle at? and if i buy a tach what wires do i connect it to.
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From: GrandRapids MI
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Postmaster
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From: Broken Arrow, OK
throttle body
Yep, the ignition coil.
If the engine runs with the screw all the way out you probably have a vacuum leak somewhere or the IAC is sticking open.
If the engine runs with the screw all the way out you probably have a vacuum leak somewhere or the IAC is sticking open.
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Postmaster
Joined: May 2002
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From: Broken Arrow, OK
throttle body
It would have to be a large leak to cause a miss at anything less than 1/2 throttle. Check the PCV hose that comes out the lower part of the plenum on the passenger's side and goes to the back of the valve cover. That's the only single hose I can think of that could cause a vacuum leak that large. The brake booster hose could also, but you would notice that the brakes don't work very well.
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Junior User
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From: GrandRapids MI
throttle body
ok my engine idles at 19inhg when it misses it goes to 18inhg if i rev the throttle it goes to about 25inhg then up to about 4 or 5 inhg then back to 19 ........ how do i check for vacuum leaks
IAC can i check this somehow clean it or will i have to replace it if it is sticking open
IAC can i check this somehow clean it or will i have to replace it if it is sticking open
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Joined: Jun 2002
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From: redding U.S.A.
throttle body
you can clean the IAC with a bottle of carb cleaner (not the whole bottle, hehe) that will help if move more freely, but it may also simply be broken.
To check it you need to take it off, and at that point spraying with carb cleaner is an extra 10-15 seconds worth of effort, so you might as well.
To check it you need to take it off, and at that point spraying with carb cleaner is an extra 10-15 seconds worth of effort, so you might as well.