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Unread 01-29-2016, 10:06 AM   #1
dastro123
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1980 CJ7 
 
Join Date: Apr 2008
Location: columbus
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Whistling Sound??

I just bought a '85 CJ7 Laredo with MPFI with 112K miles. In certain instances, it makes a whistling sound which is coming from the engine compartment.

It does it under light to medium acceleration, never under heavy throttle and only when moving. When it is happening, if I push just slightly more on the gas, the pitch changes a little, then if i let up a little the pitch changes again. It's loud enough to be annoying but the radio drowns it out. It's like it only happens within a certain throttle range, not under light or heavy throttle.

I just had the air intake completely redone so that's probably not it. I've read some other posts from people experiencing the same thing but didn't really see any fix or specific problem discovered.

I'm also unsure if it could be specific to the fuel injection system or not.

Thanks!

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Unread 01-29-2016, 10:23 AM   #2
thord
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1986 CJ7 
 
Join Date: Feb 2009
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Posts: 218
my drivers side rear view mirror whistles ever so slightly and ever so annoying. If you are sure its coming from the engine bay, I will let an expert help you

happy friday
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Unread 01-29-2016, 10:28 AM   #3
Stumblebum
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1982 CJ7 
 
Join Date: Dec 2012
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Check for intake manifold leaks. Tighten intake manifold bolts to FSM specs to see if the whistling stops or is minimized. A long term fix is replace the gasket with anaerobic (765-1189 NAPA) sealant. It's not unusual for the MPFI intake manifold bolts with a gasket to loosen over time.
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Unread 01-29-2016, 10:46 AM   #4
MOPARLICIOUS
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1985 CJ7 
 
Join Date: Jun 2015
Location: Boulder Creek, CA
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I would like to know what this sound is as well. I have a 85 CJ7 with MPFI kit also. I notice the same whistling sound when on throttle and can change the pitch if you press or let off gas pedal. I seem to hear it coming from under neath driver side where Catalytic is. This sound is annoying.
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Unread 01-29-2016, 09:38 PM   #5
258
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1985 CJ7 
 
Join Date: May 2013
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Cj

First thing that comes to mind is a LOOSE fan belt. At the belts longest stretch, see that it ONLY has a 1/4"-1/2" play.
A loose belt will make a high pitched squeal that goes away when the belt isn't slipping; usually at higher speeds.

Also, check the pulley bearings.
The way to check is to get a LONG tool and CAREFULLY place it on the pulley bolt when the engine is running. You can use a wooden dowel as well. BE VERY CAREFUL & ALERT . . . it's a running engine.
Put your thumb on the other end and place your ear into your thumb. You will definitely hear a grind if its bad. They TOO squeal when they are bad and get HOT.
Do not replace your metal pulleys with a cheap plastic pulley. Remove yours and simply replace the inner bearing. it is an easy fix. Once you have the bearing replaced, if it is that, you will be surprised at the difference in noise.

It could also be your clutch/flywheel viewing shield if the noise is down below. The shield bolt might simply need to be tightened.

Good Luck
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Unread 01-29-2016, 09:46 PM   #6
Chrisinchwk
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1982 CJ7 
 
Join Date: Jul 2015
Location: Chilliwack, British Columbia
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I had a similar sound on my 258 with a bbd after I rebuilt it. Turns out the throttle plates down inside the carb. Adjusted them a little more and it went away. Maybe. Not your problem but anything helps.
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Unread 01-29-2016, 11:12 PM   #7
gmakra
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1985 CJ7 
 
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Location: Chicago area
Posts: 3,442
Look under the throttle body and see if there is a 1 aluminum spacer in between the throttle body and manifold.
A few years back that was the rage thinking that it helped straighten air flow.
If you have one you can remove it with no bad effects.
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Unread 01-30-2016, 01:07 AM   #8
Matt1981CJ7
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1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
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I'm guessing you have a *open* style breather. Correct?

http://www.jeep-cj.com/forums/f2/whi...erating-23151/

Just another reason I'm not a fan of those.

Matt
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Unread 02-01-2016, 02:19 PM   #9
dastro123
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1980 CJ7 
 
Join Date: Apr 2008
Location: columbus
Posts: 15
Okay, just heard from Bennie at Hesco, here is what he says causes the whistle sound: "The whistle is created by air flow over the throttle plate and the air cut out for the idle speed motor. You may be able to lessen the noise by sanding the edge so it isn’t so sharp. This noise is prevalent with open air systems versus stock air boxes.
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Unread 02-01-2016, 03:38 PM   #10
Matt1981CJ7
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I love when we get one correct.

At least it's nothing serious.

Matt
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