rough idle
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rough idle
89 f150, 4.9 liter, 5spd. 169k miles....
when i first start the truck... the rpms kick up to 1800 or so and drop to about 1000-1300 when its warming up... after like 30 -45 seconds, the rpms drop but the idle gets rough... it will go from 1000 rpms to like 400 and almost stall and kick back up... it will do this for a while or if i start driving it will go away...
any ideas?
when i first start the truck... the rpms kick up to 1800 or so and drop to about 1000-1300 when its warming up... after like 30 -45 seconds, the rpms drop but the idle gets rough... it will go from 1000 rpms to like 400 and almost stall and kick back up... it will do this for a while or if i start driving it will go away...
any ideas?
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a friend of mine who is a mechanic said to get some fuel injector cleaner... and clean the idle speed motor and throttle body.... that could fix this problem?
anyone else heard of that?
thanks
anyone else heard of that?
thanks
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Being that it is an 89 model it has Fuel injection and not a carb. Thus there is no "electronic choke"
The reving up is quiet normal, then it will fall back down to the normal range. it shouldn't fall so low though that it stats to stall.
It sounds like it might be your IAC (idle air control) valve. this controls the amount of air that bypasses the throttle body and controls the idle.
These can get built up with carbon and stick a little bit. No big deal though it is easy to take off and clean. won't take more than a few minutes.
The IAC valve is located on top of your throttle body. it is a little round cylinder with an electric plug connected to it.
Here is a picture of one on Ebay. This is one off of a Mustang, but yours will look almost identical.
http://cgi.ebay.com/ebaymotors/Polis...spagenameZWDVW
Remove the 2 screws attatching it to the throttle body. Once you remove the valve, look inside it and you will see a little rodd that moves back and forth. See if there is any build up on it. If so just take some cleaner and a toothbrush and clean it out real good. I have found that gun cleaner breaks down the carbon the best, but cleaning solvent should work.
The reving up is quiet normal, then it will fall back down to the normal range. it shouldn't fall so low though that it stats to stall.
It sounds like it might be your IAC (idle air control) valve. this controls the amount of air that bypasses the throttle body and controls the idle.
These can get built up with carbon and stick a little bit. No big deal though it is easy to take off and clean. won't take more than a few minutes.
The IAC valve is located on top of your throttle body. it is a little round cylinder with an electric plug connected to it.
Here is a picture of one on Ebay. This is one off of a Mustang, but yours will look almost identical.
http://cgi.ebay.com/ebaymotors/Polis...spagenameZWDVW
Remove the 2 screws attatching it to the throttle body. Once you remove the valve, look inside it and you will see a little rodd that moves back and forth. See if there is any build up on it. If so just take some cleaner and a toothbrush and clean it out real good. I have found that gun cleaner breaks down the carbon the best, but cleaning solvent should work.
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thank you VERY much... that sounds very similar to what the mechanic guy told me, i just must have remembered the name wrong....
he said fuel injector cleaner... i dont have gun cleaner... what else would work??
thanks a million
he said fuel injector cleaner... i dont have gun cleaner... what else would work??
thanks a million
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Joined: Jun 2001
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Originally Posted by 1989BIG6
he said fuel injector cleaner... i dont have gun cleaner... what else would work??
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i cleaned the IAC and def removed a good amount of build up. i also wiped down the throttle body.
results... def. improved but not completely gone. i understand it will initially kick up the rpms when the engine starts but once it idles down, it still have a little variation... maybe like 200 rpms (before it was like 5-600 rpms)
any ideas?
thanks
results... def. improved but not completely gone. i understand it will initially kick up the rpms when the engine starts but once it idles down, it still have a little variation... maybe like 200 rpms (before it was like 5-600 rpms)
any ideas?
thanks
More Turbo
Joined: Jun 2001
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Originally Posted by 1989BIG6
it still have a little variation... maybe like 200 rpms (before it was like 5-600 rpms)
I think mine idles between 600-800 so that much might be perfectly normal.
The only other thing I can suggest is to check for a slight vacuum leak. possibly check around the throttle body gaskets and all the vacuum hoses coming off of the intake manifold. Mine have been known to dry rot and get hairline cracks in them.
