1998 Dodge Dakota 3.9 Liter Vacuum Diagram

Desember 06, 2021

From Message shdow
Dodge Dakota
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7/09/2005
17:53:09

Subject: 1998 vacuum lines
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this v6 3.9 1998 has a vacuum line plugged for some reason and I see no obvious route as to were it has been disconnected from

its nipple on the intake is just below the pcv valve vacuum hose coming from intake no tees two sep nipples on top of each other 1" apart

I think it was plugged to fool the emissions inspection machine

any ideas it does affect rpms when I remove the plug

TIA Forseti
Dodge Dakota
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7/10/2005
11:19:46

RE: 1998 vacuum lines
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Thats normal .... my truck has it too I believe they are just test ports

Sully Erna
Dodge Dakota
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7/14/2005
20:52:37

RE: 1998 vacuum lines
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I have to plug this nipple in the winter and put a vacuum hose with a little filter on it during the summer. In the winter without a nipple, if I rev the motor the rpm's take about 5 to 7 seconds to come back to idle. If I have it plugged during the summer and rev it, it kills the engine. I have asked this question here before and someone said "you get zero mpg by revving it while parked". Not what I was looking for. So I would also like to know what is this port for?

Gregg
Dodge Dakota
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7/14/2005
21:36:58

RE: 1998 vacuum lines
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Sully, can you qualify the location of the hose/plug nipple? Is it (facing engine) on the left side intake area, about 1/4 hose dia.?

I think it's blocked from the factory. Perhaps a test point or vacuum source for a mystery accessory.

With the cap off in any season, the idle should climb as it's a way huge vac-leak! Not sure what the screen deal does for you other than add more air to it's intake. The computer would see it as a lean condition and try to spout more fuel into the mix. Strange.

Hmmm, I believe you have an anomoly. Sully Erna
Dodge Dakota
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7/24/2005
19:08:43

RE: 1998 vacuum lines
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It is the nipple/port just under the PVC valve port. You would think that it would have a vac-leak without a nipple on it but that does not seem to work when it gets hot outside?????? I just put a little breather filter on it so it does not get crap in the intake manifold. I will just have to put a cap on it when winter comes.

Forseti
Dodge Dakota
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7/24/2005
22:26:48

RE: 1998 vacuum lines
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Cap the nipple do not leave the breather on it. They are just test ports you will run lean and bypass the function of the IAC on the TB.......cap it

nododge
Dodge Dakota
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8/29/2010
02:49:47

97 dakota 3.9 vacuum port
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I have a 3.9 v6 that has vacuum nipple on the left side of the intake manifold that has nothing connected to it. with the engine on, if i put my finger on the port hole, the engine dies. what is this port for?

Rcfuss
Dodge Dakota
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4/09/2011
23:32:35

RE: 1998 vacuum lines
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Thanks to whomever runs this server/forum for keeping this info on here.

Forsetti is right and keep the vacuum port plugged.

My check engine light was on due to the secondary o2 sensor (after the cat.). The guy at the autopart store said the code meant bad o2 or car is running rich

I just replaced the o2 sensors under a year ago and was questioning whether or not the replacement part was defective.

When I was changing oil today I was just inspecting the engine for leaks and heard that test port. I plugged it and the check engine light went away.

Forsetti just put 2 and 2 together for me. The o2 wasn't bad it was the test port not being plugged that set off the check engine light because the car was running rich.

mhak74
Dodge Dakota
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5/06/2011
08:58:00

RE: 1998 vacuum lines
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Thanks for all the info on this! I've been hearing a hissing for a while now and could never pinpoint the thing until I read this. I took a look and sure enough there was a small cap laying right underneath the nipple. I've also been having troubles starting the truck in rain/humidity and after changing the distributor cap and rotor I thought I had it licked but still I had starting issues. Do you think not having the nipple capped would cause starting issues in humid weather?

J.W.PARKER
Dodge Dakota
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2/15/2015
07:30:13

RE: 1998 vacuum lines
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climate controll switch not working blowes out of defost&floor can not find vacuum line on 5.2 motor going to controll switch

1988 Dodge
Dodge Dakota
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4/09/2017
20:37:29

RE: 1988 vacuum lines
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I have an 88 dodge Dakota 3.9l V.6. I'm having some trouble
locating a diagram for the vacuum lines to and from the
engine/tranny. It's shifting very hard possible vacuum line
leak??

Mr. Fixit
Dodge Dakota
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2/07/2019
22:04:52

RE: 1998 vacuum lines
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It is called a 4x4 climate control valve.
You should ask your local Dodge dealers.
Also stop by an exhaust shop as you may
well have debris inside the exhaust
system.

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