3.9 vacuum leak? - DodgeForum.com

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3.9 vacuum leak?

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  #1  
Old 09-17-2018, 01:00 PM
restlessswind
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Default 3.9 vacuum leak?

Ok, I've tried and tested everything,and can't find what appears to be a vacuum leak in the manifold. I plugged off all vac lines from the manifold and TB. Still rough idling. I ran the crankcase pressure test too. I get positive pressure and no oil pooling in the plenium. Ideas? Suggestions? Anyone else run into this situation before?
 
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Old 09-17-2018, 03:15 PM
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What is manifold vacuum at idle?
 
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Old 09-17-2018, 07:58 PM
restlessswind
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Hey You, it's the Dakota guy you've been assisting me with. Thanks for your help! Much appreciated! Anyway, it's 19 in Hg pulled from the plenium port, and the MAP reading is 5 psi
 
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Old 09-17-2018, 08:02 PM
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Hey You, it's the Dakota guy you've been assisting me with. Thanks for your help! Much appreciated! Anyway, it's 19 in Hg pulled from the plenium port, and the MAP reading is 5 psi.

It's also smelling rich when cold ( open loop)
 
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Old 09-18-2018, 09:20 AM
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That's actually quite close to where it should be. The map reading seems a little off though..... (by about 50%) is the little rubber elbow from the throttle body to the map damaged?
 
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Old 09-18-2018, 10:15 AM
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No. It seals fine. The symptoms don't go away, even when cold if I remove every single vacuum line coming off the intake stack, and plug the ports off, including the MAP sensor.
 
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Old 09-18-2018, 11:36 AM
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What are your symptoms?
 
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Old 09-18-2018, 02:49 PM
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rough/shakey idle at all temps and rich when cold. (idle warmed up is about 670 RPM. It holds idle well and same 670 in gear, or not, and with A/C on or off.)
Cold idle is about 900 RPM
 
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Old 09-18-2018, 02:50 PM
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Is there a way to test the accuracy of the MAP sensor?
 
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Old 09-18-2018, 08:35 PM
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Compare the reading you are getting from the vacuum gauge, do some math, (convert in/hg to psi, or whatever measurement the PCM reports) and see if they are even close.....

How old are your tune up parts? What plugs ya got in there? Are the wires routed per the TSB?
 
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