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'96 Explorer Vacuum Leak

MPNX2

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July 11, 2009
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Year, Model & Trim Level
1996 Explorer
Ok I seem to have a vacuum leak on our 96 Explorer. It is the V6 4.0 liter engine. At times it will idle really rough does not seem to matter if it is cold of warm. I can make it idle this way by pumping the brakes over and over which tells me it is a vacuum leak. Now I have tested the IAC on the top of the intake. I unplugged it and the idle became much worse. So this would tell me it is working. If I spray starting fluid around different areas if I spray it by the AC compressor the idle will raise. There is an audible hissing sound in this area. I cleaned the IAC and no change. I thought I had a leak at the IAC so I siliconed around it but no change. Is there a gasket that goes on the IAC? There is a line by the AC compressor which plugs in right behind where the intake butterfly is. This hose runs down under the battery where alot of hoses meet I am unsure what that is. But this is the area where the idle will raise if starting fliud is sprayed. So it that a vacuum line? Vacuum leaks sure are frustrating can anyone help out?
 



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there is an evap line that connects underneath the throttle body, this sounds like what you are talking about. But, i believe your leak might be around the egr tube, i have a 96 4.0 also, and this is where my vacuum leak was. It is the big metal pipe that goes from the upper intake down to the egr valve and it is behind the ac compressor. It was leaking where the pipe goes into the upper intake manifold.
 






I can make it idle this way by pumping the brakes over and over which tells me it is a vacuum leak.
Check the brake booster.
 






Is there a gasket that goes on the IAC? ?

Yes, there should be a gasket or o-ring where the IAC mounts to the intake manifold. On my 97, it is a figure-eight shaped rubber o-ring gasket.
 






there is an evap line that connects underneath the throttle body, this sounds like what you are talking about. But, i believe your leak might be around the egr tube, i have a 96 4.0 also, and this is where my vacuum leak was. It is the big metal pipe that goes from the upper intake down to the egr valve and it is behind the ac compressor. It was leaking where the pipe goes into the upper intake manifold.

This sounds like it could be the problem. How did you reapir the metal pipe? Did you just replace it?
 






you have to unbolt the pipe from the egr valve and unbolt the upper intake manifold, lift up the intake, then pull out the pipe. There will be an oring gasket around the end of the pipe on the intake end.
 






Thank you Team.

Just for an update I borrowed a OBD2 reader from a friend and there were no codes to display. I know the check engine light wasnt on but it was worth a shot. Also, I checked the brake booster by letting the engine idle for a few minutes then shutting it off and pulling the line off of the brake booster and the was an auidble hiss meaning the vacuum was still present and not leaking.
Here is a pic of the line that I think is the cause....

IMG_3744-1.jpg
 






that pic is of the evap. system line. If you really think that is the leak then unhook it and put a vacuum cap over the tube coming out of the throttle body. If your vacuum leak is gone then you found it.
 






that pic is of the evap. system line. If you really think that is the leak then unhook it and put a vacuum cap over the tube coming out of the throttle body. If your vacuum leak is gone then you found it.


Thanks again Team..

I am going to try this tonight. I hope it is something simple like that. I have been told that there are O rings in that connector that can dry up and crack. How does that connector come apart. It looks like it needs to br pryed arart...
 






you pull the clear/white plastic duckbill connector straight out then slip the hose off.
 






Just swapped all vacuum hoses

Guys, thought I'd chime in. Replaced all vacuum hoses on my 98 XLT this weekend. Used silicone hosts from boostcontroller.com, but these can be purchased just about anywhere. They are vastly superior to rubber hoses and very easy to work with, just slice 'em with a straight razor and slide 'em on, they don't need clamps as the hose tension should hold them on.

Replaced vacuum hoses on PCV valve (8mm diameter, checked grommet for cracks), brake booster, EGR valve (two different diameter tubes, used a 6mm and a 3mm), and evap line (under throttle body). Did I miss any?

Oh, while I was at it, I replaced fuel filter and cleaned IAC and throttle body...this got rid of lean codes (before vacuum tube replacement) so go figure...most likely lean condition was due to clogged fuel filter...not sure.

CEL is off, lean codes gone, truck runs like a beast now...easy fix for sure.
 






96 Explorer vacuum leak

To MPNX2 did replacing that part under the throttle housing correct your problem. I have the exact same problem. I'm not automobile savvy and any replacement info that you guys can provide would be greatly appreciated
 


















Thank you Team.

Just for an update I borrowed a OBD2 reader from a friend and there were no codes to display. I know the check engine light wasnt on but it was worth a shot. Also, I checked the brake booster by letting the engine idle for a few minutes then shutting it off and pulling the line off of the brake booster and the was an auidble hiss meaning the vacuum was still present and not leaking.
Here is a pic of the line that I think is the cause....

IMG_3744-1.jpg
Could you tell me where that line runs too? I have mine plugged but would would like to replace with the right hose
 






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