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Old 05-06-2014, 07:31 PM
themikster themikster is offline
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Angry RPMs drop when brake applied; reverse hissing leak

Hey everyone, recently i have been noticing that when i come to a stop sign or red light and press the break normally that my Rpms will drop anywhere between 100-500 rpms and then when i hit the gas it kind of has a small jerk and the rpms jump back up and it drives fine. Does anyone know what this could be???

BTW: its a 2001 4x4 auto 4.0 v6 XLT




Another problem that has come up is when i put it in reverse (automatic) it almost sounds like the tranny is making a hisssing/vacuum leak? maybe a bad torque converter???

i have cleaned the IAC..




Any help would be more then appreciated, thanks!
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  #2  
Old 05-06-2014, 07:47 PM
Ranger Truckin Ranger Truckin is offline
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Aren't the RPMs suppose to go down when you brake
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Old 05-06-2014, 07:54 PM
themikster themikster is offline
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Not way below idle and act like it's going to die...
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Old 05-06-2014, 07:56 PM
Ranger Truckin Ranger Truckin is offline
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Oh I didn't realize you meant so low
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Old 05-06-2014, 07:59 PM
07XL 07XL is offline
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Are your brakes hard to push?
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Old 05-06-2014, 08:04 PM
themikster themikster is offline
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Not extremely hard (for a 01 I think they feel normal) they stop me that's all I care about haha
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Old 05-06-2014, 08:13 PM
dangerranger94 dangerranger94 is offline
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Quote:
Originally Posted by themikster View Post
Not extremely hard (for a 01 I think they feel normal) they stop me that's all I care about haha
more then likely your brake booster is leaking
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Old 05-06-2014, 08:15 PM
07XL 07XL is offline
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Quote:
Originally Posted by dangerranger94 View Post
more then likely your brake booster is leaking
^^
Yep that's where I was going with this lol


That's also causing a vacuum leak which is dropping your idle.
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Old 05-06-2014, 08:20 PM
themikster themikster is offline
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I will look into this more. How did you come up with the brake booster as an option? Btw: thanks for the suggestion!
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Old 05-06-2014, 08:23 PM
07XL 07XL is offline
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It's a vacuum controlled part. Low idle is typically a vacuum leak, and you said it happened when the brakes were applied. So that makes me think it's the brake booster.
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Old 05-06-2014, 08:26 PM
themikster themikster is offline
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Will look into this more.. Thanks for the input! Let me know if you think of anything else
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Old 05-06-2014, 08:32 PM
07XL 07XL is offline
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You're welcome.
Let us know how it goes.
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Old 05-06-2014, 08:34 PM
Fordzilla80 Fordzilla80 is offline
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Default Re: RPMs drop when brake applied; reverse hissing leak

When my brake booster took a shit, my idle sucked all the time, not just when I applied the brakes.

Does the truck idle like shit when you're sitting in park or neutral?
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Old 05-07-2014, 06:04 AM
themikster themikster is offline
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No it starts and idles like a champ
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Old 05-07-2014, 09:05 AM
01_ranger_4x4 01_ranger_4x4 is offline
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Default Re: RPMs drop when brake applied; reverse hissing leak

Brake booster
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