Whistle affected by throttle! Help!!

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MajorMedic44

New Member
Joined
Mar 18, 2024
Messages
4
Location
Georgia
2002 TJ. 4.0
After running about 10 minutes, a whistle appears. It disappears when I’m on throttle. When I let off something whistles loud. I’ve changed throttle body, crankcase valves, brake booster valve and all vacuum lines. I’ve also made sure my intake manifold bolts were tight. Any ideas where it is coming from?
 
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MajorMedic44 said:
After running about 10 minutes, a whistle appears. It disappears when I’m on throttle. When I let off something whistles loud.
Click to expand...

That makes me think it's a manifold vacuum source, so look around for loose lines, cracked lines or missing lines south of the throttle body. Since it does it after warm up, maybe start at the idle air valve.

MajorMedic44 said:
crankshaft valves
Click to expand...

Also, what the hell is a "crankshaft valve". Are you talking about the PCV?
 
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Mine does it on the highway, when easing off the throttle for level ground. I haven't been able to figure it out, vacuum lines and check valves are all good. I'm thinking it might be coming from the cruise control unit, do you have CC? My whistle is not too loud and it comes and goes with throttle position but only at highway speeds.
 
BlueC said:
That makes me think it's a manifold vacuum source, so look around for loose lines, cracked lines or missing lines south of the throttle body. Since it does it after warm up, maybe start at the idle air valve.



Also, what the hell is a "crankshaft valve". Are you talking about the PCV?
Click to expand...

Sorry meant crank case
 
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BlueC said:
That makes me think it's a manifold vacuum source, so look around for loose lines, cracked lines or missing lines south of the throttle body. Since it does it after warm up, maybe start at the idle air valve.



Also, what the hell is a "crankshaft valve". Are you talking about the PCV?
Click to expand...

Crankcase***
 
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I've owned two 4.0 jeeps both had that whistle my best guess is that it's a vacuum leak somewhere on the intake or they just naturally whistle when cold due to shape or internal diameter of the intake🤷‍♂️
 
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