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View Full Version : What is the correct vacuum for a 97+ 4.0L engine?


Mudderoy
07-01-2011, 12:47 PM
As it always happens, when I get something new, especially if it is something that measures something I'll post up what is normal!

My 1998 Jeep XJ 4.0 with 170k miles idles about 750 rpm and run a vacuum of 17.
Mudderoy
07-01-2011, 12:54 PM
lol while doing a search I see I asked this same question before, but on CherokeeTalk. I never got an answer.

:link: (http://www.cherokeetalk.com/forum/f8/4-0l-normal-intake-manifold-pressure-2053/)
xj4life2
07-01-2011, 03:14 PM
17 to 21 at idle is the spec , 25 at decel and 3 to 5 at hard acceleration. This will fluctuate based on the condition, age of the motor.
Mudderoy
07-01-2011, 05:50 PM
17 to 21 at idle is the spec , 25 at decel and 3 to 5 at hard acceleration. This will fluctuate based on the condition, age of the motor.

This is excellent information and more than I asked for! :thanx:
Mudderoy
07-13-2011, 04:50 PM
17 to 21 at idle is the spec , 25 at decel and 3 to 5 at hard acceleration. This will fluctuate based on the condition, age of the motor.

After the replace gauge installed...

17 at idle
15/16 in drive

21/22 decelerate

2/1 hard acceleration (it may be 0!)