High idle after cleaning Throttle Body
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Joined: Aug 2014
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Lets take the time to go over how to describe an issue.
1. Describe accurately what is happening along with any codes.
Truck idles between 800 and 900 rpm's. Recent "pending " codes were due to me unplugging IAC.
2. Do not include any long history because what is happening now is what's important.10-4
3. Do not fall back on what parts or work was done weeks or months ago 'that could not be an issue'.Replaced the IAC a few days ago.
4. Do not ask whys or what ifs on the problem trying to second guess it before the trouble is solved for.Not exactly sure what that means. I'm asking for help because i need insight into a motor that I am unfamiliar with. I do have enough rudimentary mechanical skill to forge ahead while checking here to see if someone might have a magic bullet.
5. Do not rely on 'it looks good', be sure.I have been systematically pulling vacuum lines and plugging them to see if the idle changes.
.
We need the above to have any chance of accurately providing diagnosis, then you need to carry out the suggestions and report the results.
This is the help you come to ask for and how it is rendered.
Good luck.
1. Describe accurately what is happening along with any codes.
Truck idles between 800 and 900 rpm's. Recent "pending " codes were due to me unplugging IAC.
2. Do not include any long history because what is happening now is what's important.10-4
3. Do not fall back on what parts or work was done weeks or months ago 'that could not be an issue'.Replaced the IAC a few days ago.
4. Do not ask whys or what ifs on the problem trying to second guess it before the trouble is solved for.Not exactly sure what that means. I'm asking for help because i need insight into a motor that I am unfamiliar with. I do have enough rudimentary mechanical skill to forge ahead while checking here to see if someone might have a magic bullet.
5. Do not rely on 'it looks good', be sure.I have been systematically pulling vacuum lines and plugging them to see if the idle changes.
.
We need the above to have any chance of accurately providing diagnosis, then you need to carry out the suggestions and report the results.
This is the help you come to ask for and how it is rendered.
Good luck.
Thread Starter
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Joined: Aug 2014
Posts: 16
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Yea, if you can view those DTC's, they're not pending in a sense you may be thinking. All that means is the problem is there, what's pending, is you fixing it.I did. I plugged the IAC back in after seeing what affect it had on the idle.
Appreciating is one thing, acting on it is another. Since everything has been covered, -time for you to do something.
Do something? You mean something else, right? I've troubleshot the vacuum lines, replaced the IAC, removed and reassembled the air cleaner assembly and insured that all vacuum lines are properly secured. Cleaned and lubed the throttle body again. Re calibrated my scan gauge to look for throttle position.
BTW- Yes, please post the problem, honestly if you can.
Appreciating is one thing, acting on it is another. Since everything has been covered, -time for you to do something.
Do something? You mean something else, right? I've troubleshot the vacuum lines, replaced the IAC, removed and reassembled the air cleaner assembly and insured that all vacuum lines are properly secured. Cleaned and lubed the throttle body again. Re calibrated my scan gauge to look for throttle position.
BTW- Yes, please post the problem, honestly if you can.
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
To be very honest your not understanding the operation.
I was trying not to get to deep into this but maybe I need to.
First, excessive air raising the idle won't be due to a vacuum leak as much as you might be inclined to view them as one and the same.
.
Reason: the conditions each set up are totally different so you see a different end result for each condition.
Why:
If there are 'no vacuum leaks', the fuel tables will 'not' be shifted trying to add more fuel, and Ox sensors do not see anything out of A/F limits.
Air getting by the throttle body will then raise the idle speed as would be normal.
.
However, if there (is) a vacuum leak, the OX sensors detect this as a lean condition and attempt to add fuel via the fuel tables. This WILL set codes 171/174, cause idle instability and stalling because the idle air fuel mix is all wrong because it cannot be corrected.
.
You now see there are two different conditions.
If you have no codes set for Lean and Long term trim tables are not shifted then there are no vacuum leaks.
.
With high idle you have air getting by the throttle plate for some reason.
The Mass Air meter is measuring it so all is fine except YOU know the idle is too high from normal knowledge. The motor does not care at this point because it's monitors see nothing out of order.
.
Finding vacuum leaks with spray cleaners.
Some cleaners are non combustible so will not be of any value listening for an idle change.
The proper way to find a leak with the right combustible spray is to first know the fuel tables are shifted using a Scanner to0 look.
Then you watch the short term fuel trims for reaction as you spray the leak area.
The OX sensors react immediately as they are designed to do under normal running.
Cleaver? Not?
.
The 18.4 is about normal. It is a reading of the TPS position.
.
You see how much there is to all this.
When your not well informed it seems very confusing and you miss part of the whole action.
Hope this is of value.
Good luck.
I was trying not to get to deep into this but maybe I need to.
First, excessive air raising the idle won't be due to a vacuum leak as much as you might be inclined to view them as one and the same.
.
Reason: the conditions each set up are totally different so you see a different end result for each condition.
Why:
If there are 'no vacuum leaks', the fuel tables will 'not' be shifted trying to add more fuel, and Ox sensors do not see anything out of A/F limits.
Air getting by the throttle body will then raise the idle speed as would be normal.
.
However, if there (is) a vacuum leak, the OX sensors detect this as a lean condition and attempt to add fuel via the fuel tables. This WILL set codes 171/174, cause idle instability and stalling because the idle air fuel mix is all wrong because it cannot be corrected.
.
You now see there are two different conditions.
If you have no codes set for Lean and Long term trim tables are not shifted then there are no vacuum leaks.
.
With high idle you have air getting by the throttle plate for some reason.
The Mass Air meter is measuring it so all is fine except YOU know the idle is too high from normal knowledge. The motor does not care at this point because it's monitors see nothing out of order.
.
Finding vacuum leaks with spray cleaners.
Some cleaners are non combustible so will not be of any value listening for an idle change.
The proper way to find a leak with the right combustible spray is to first know the fuel tables are shifted using a Scanner to0 look.
Then you watch the short term fuel trims for reaction as you spray the leak area.
The OX sensors react immediately as they are designed to do under normal running.
Cleaver? Not?
.
The 18.4 is about normal. It is a reading of the TPS position.
.
You see how much there is to all this.
When your not well informed it seems very confusing and you miss part of the whole action.
Hope this is of value.
Good luck.
Thread Starter
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Joined: Aug 2014
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This is very good information and I do understand exactly what you are saying. My throttle plate has a small hole (1/16" dia?) right in the middle of it, upperhalf, looks to be factory. And thanks for verifying the TPS%. Edit - I've heard of old carburetors ( like the one on my 1950 Flathead 8BA) leaking air around the plate shaft. Seems after years of wear, air gets in around the space created. Anything ever happen like that to the 4.6 throttle body or are the shaft ends sealed? Edit - Checked photos online, they all have that little hole. Also read this little nugget on a factory TB: Attention: Do not clean inside throttle body or adjust hard stop screw. Special coating on throttle plate and bore.
Last edited by F91; Sep 29, 2014 at 10:26 PM.
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
Likes: 19
From: MI
Back at yuh.The information you sought was explained here. What do you do; - later you repeat the info already given, then give credit to another site and ask if we agreed with it...WTF?
That's some kind of strange.
Do you really want help from here?
I have a feeling you are your own worst enemy.
Thread Starter
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Joined: Aug 2014
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Well It's fixed by my own worst enemy. Don't know why you are a hostile guy Jbrew, what your deal is, but again, I appreciate everyone's help, even yours . The issue isn't, nor ever was using harsh chemicals, smoking a sensor ribbon or anything like that. The throttle body is fine. It's the PCV tube-valve- elbow.
Do I really want help here? Ummmmm, yes, that's why I asked the question. And yes, I asked about info that was posted on several sites and there are several posters that are members of those sites that post here too. I'm sorry that, you know, me working 14 hour days and all, working on my truck till dark, that I cannot keep up with everything that I posted straight, but I do know this: The god damned thing is fixed. Peace.
Do I really want help here? Ummmmm, yes, that's why I asked the question. And yes, I asked about info that was posted on several sites and there are several posters that are members of those sites that post here too. I'm sorry that, you know, me working 14 hour days and all, working on my truck till dark, that I cannot keep up with everything that I posted straight, but I do know this: The god damned thing is fixed. Peace.
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Joined: Aug 2014
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You're right grizz, wasn't the TB at all. The PCV tube on the passenger side was bad. Fixed. BTW - You have a Mustang? I've got a 2011 GT with a coyote. Love my Fords!
