Vacuum leak

[xjjunkie]

Re: RE: Ok i have finally picked which lift

Please help!..I have an 89 jeep cherokee limited,4.0,automatic.For the longest time now,my jeep has been running rough..I can hear what sounds to be a vacuum leak,but can not seem to find it.Is it possible that the intake manifold is cracked?Is this common?Ihave checked and rechecked everything!please help,any info would be greatly appreciated..
Ijust recently replaced the fuel injectors,o-rings,plugs,wires,cap,rotor,fuel filter,ignition module,coil,and crank sensor....thanks for all the help in advance...hopefully

 

[berettajeep]

First thing.
Use some heater hose.

Now with the engine running carefully run one end of the heater hose along all vaccum lines and hold the other end of the heater hose to your ear.
If you find nothing go over the whole engine.

PLEASE BE EXTREMELY CAREFUL AROUND THE MOVING ENGINE PARTS.

 

[Sly8795]

RE: lesson to be learned

I'm not sure this will work but i heard from my brother who works along side a bunch of mechanics that you could spray a little bit of carb cleaner around vacuum areas and if the engine revs up youve found your area because the engine will possibly suck in the cleaner and rev. If this is wrong or a different method is used please go right ahead and shoot my suggestion down.

 

[Bounty__Hunter]

Get an LP bottle like the plumbers use to sweat pipe fittings. Turn on the tank and run the unlit LP over anywhere a vacuum leak is possible. It's cleaner than carb cleaner and you'll get an idle increase when you find the leak.

 

[90Xjay]

89-90 were pretty bad about leaking vacuum right in front of the pass side firewall is some vacuum lines one of them is kinda pink and very small. About the diameter of a coffee stir stick. Those rot and leak.

You can just trim them back to where it is good and then slip some rubber vaccum line with similar ID as your leaker lines OD.

Do yourself a favor and look there. And I agree with BH on the propane method.


90

 

[xjjunkie]

Ive replaced any of the vacuum lines that were in any way questionable,still same problem.I am very mechanically inclined,and am generally very good at diagnosis,but this has be stumped...and quite aggravated.I can hear a very prominent vacumm leak from the driver side of the motor,yet have tried all the methods of locating the leak to no avail! Heres my question,....Are the intake manifolds on an 89 cherokee 4.0 know to crack????...im thinking that is my next step ,replace the intake manifold and gasket.What do you all think???? im stumped..please help...thank you very much!

by the way..im new at this board,but i have already found it to be invaluable.!!

 

[90Xjay]

I have never known of a problem with an intake manifold itself.
You know that these 4.0's share a common intake/exhaust gasket and the both manifolds share bolts. The intake is held inplace by the exhaust manifold bolts with big mushroom shaped washers. Could be just a bad seal/gasket leak....