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Old 09-15-2015, 06:37 PM   #1
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Hanging RPMS

Hey guys, I'm new to this page. I could use some help diagnosing my problem with hanging rpms. My 2004 GT had rarely done this so I never paid attention to it. Recently I just installed a BBK 78mm TB/Plenum and my rpms are hanging really bad. I will take it out of gear coming to a stop sign or red light and my rpms stick at 1500rpm and slowly drop down to normal idle when I'm at a complete stop. My car is also Bama tuned but I do not believe the tune is causing this. What could it be?
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Old 09-15-2015, 07:48 PM   #2
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I have the exact same TB and BBK is known for the throttle plate sticking. The reason why your RPM's hang is because the vacuum of the throttle plate isn't adjusted correctly. Did you adjust the throttle screw?
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Old 09-15-2015, 08:05 PM   #3
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Mine did it too, just make sure your vac lines are seated right.. Not a big issue, easy fix
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Old 09-15-2015, 08:12 PM   #4
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Originally Posted by Kris.R View Post
I have the exact same TB and BBK is known for the throttle plate sticking. The reason why your RPM's hang is because the vacuum of the throttle plate isn't adjusted correctly. Did you adjust the throttle screw?
What exactly is my throttle screw? Sorry I'm not too knowledge on stuff like this.
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Old 09-15-2015, 08:27 PM   #5
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Throttle screws are set from the factory. Don't mess with them! Or you'll screw yourself. They ain't like a throttle screw on a carb!


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Old 09-15-2015, 08:41 PM   #6
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I didn't touch anything like that. But if that's what's causing my hanging rpms then shouldn't it be adjusted? I've read where I may need to adjust my TPS voltage but I'm not sure how to do that.
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Old 09-15-2015, 08:49 PM   #7
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It should just be the vac lines if you didn't touch anything else
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Old 09-15-2015, 08:52 PM   #8
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So what should I do to fix it?
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Old 09-15-2015, 09:27 PM   #9
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Originally Posted by Vaughan1023 View Post
So what should I do to fix it?
Go to post #9

Throttle body screw - Ford Mustang Forum

Your vacuum lines have nothing to do it with it. BBK is known to not machine the bore of the TB where the plate is housed properly. Just search on google and you'll find TONS of threads from different forums about your issue.

The whole "factory setting" for the throttle plate isn't something to be religious about as there can always be a simple error in assembly that could cause your issue. It never hurts to check.

As far as adjustment goes, when you look at the top of your TB you'll see the screw. Get a feeler gauge in there and check for proper clearance

Ex.
http://www.vtcoa.com/forums/attachme...e-photo-1-.jpg
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Old 09-16-2015, 04:27 AM   #10
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did you pull your battery to reset your computer? because the sudden change in airflow will confuse it.
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Old 09-16-2015, 08:34 AM   #11
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Quote:
Originally Posted by Vaughan1023 View Post
Hey guys, I'm new to this page. I could use some help diagnosing my problem with hanging rpms. My 2004 GT had rarely done this so I never paid attention to it. Recently I just installed a BBK 78mm TB/Plenum and my rpms are hanging really bad. I will take it out of gear coming to a stop sign or red light and my rpms stick at 1500rpm and slowly drop down to normal idle when I'm at a complete stop. My car is also Bama tuned but I do not believe the tune is causing this. What could it be?
Hey Vaughan1023 - Welcome to MustnagEvolution. Sorry to hear that you're running into trouble. I'd have to side with the rest of the fellas in here and I would start right with the throttle intake.

If this were a cold air I would start by hunting for a loose line but what's happening isn't in direct relation to the problem at hand and you're going to need to take a look at your tps.

This is a super, super common issue and the link for the post below should get you set up.

If you're having any trouble with this shoot my customer service team a call and they're happy to get you some help.

Let us know how you make out.

Alex

Quote:
Originally Posted by Kris.R View Post
Go to post #9

Throttle body screw - Ford Mustang Forum

Your vacuum lines have nothing to do it with it. BBK is known to not machine the bore of the TB where the plate is housed properly. Just search on google and you'll find TONS of threads from different forums about your issue.

The whole "factory setting" for the throttle plate isn't something to be religious about as there can always be a simple error in assembly that could cause your issue. It never hurts to check.

As far as adjustment goes, when you look at the top of your TB you'll see the screw. Get a feeler gauge in there and check for proper clearance

Ex.
http://www.vtcoa.com/forums/attachme...e-photo-1-.jpg
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Old 09-17-2015, 12:45 AM   #12
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Hope it all worked out Vaughan.
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Old 09-17-2015, 08:33 AM   #13
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Thanks guys. I think I've solved it actually. My IAC Valve is faulty. I have a tuner that clears my CEL so I forgot I could check codes. I'm pulling a faulty iac code and tps code for low voltage. Once again, thanks for all your help!
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Old 09-17-2015, 08:21 PM   #14
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Awesome! Glad it was resolved.
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