EVAP Vacuum Leak Down Question

box12360

box12360

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Joined
Nov 12, 2018
Messages
55
Location
Florida
2003 4.0 Automatic, no engine light (still need to check for codes..)

After my motor warms up it idles around 500 rpm. I can hear a whistle when I'm accelerating starting at about 2k rpm. It hesitates from a stop for 1-2 sec then goes.

Things I've done so far:

1. Thoroughly cleaned throttle body and all components connected to it , ( actually got a junkyard one as well and replaced the old one)
2. Replaced vacuum line going to reservoir and ac system.. Tested with pump no leak down
3. Changed spark plugs.
4. Tested vacuum line from intake going to purge solenoid valve- It is leaking down.

Is that line supposed to hold to vacuum? Has anyone had this problem and trouble shoot it?
Is the purge solenoid valve or the lines known to go bad not able to hold vacuum?
Can I cap this off at the intake to see it runs better?
 
box12360 said:
2003 4.0 Automatic, no engine light (still need to check for codes..)

After my motor warms up it idles around 500 rpm. I can hear a whistle when I'm accelerating starting at about 2k rpm. It hesitates from a stop for 1-2 sec then goes.

Things I've done so far:

1. Thoroughly cleaned throttle body and all components connected to it , ( actually got a junkyard one as well and replaced the old one)
2. Replaced vacuum line going to reservoir and ac system.. Tested with pump no leak down
3. Changed spark plugs.
4. Tested vacuum line from intake going to purge solenoid valve- It is leaking down.

Is that line supposed to hold to vacuum? Has anyone had this problem and trouble shoot it?
Is the purge solenoid valve or the lines known to go bad not able to hold vacuum?
Can I cap this off at the intake to see it runs better?
Click to expand...

I had problems with my lines that attach on the underside of the intake manifold. They (the 90 elbows) were cracked and causing my leaks. I also checked the lines going to the vac box that sits under the battery hold . that elbow was cracked as well.

You should be able to cap off the inlet/outlet under the intake and see if that changes the running.

Ray
 
The line from the intake to the Purge valve should hold vacuum with the engine off (or the solenoid unplugged). If it does not then either there is a leak in the line or the purge valve is not seating properly.
 
WWII Jeeper said:
I had problems with my lines that attach on the underside of the intake manifold. They (the 90 elbows) were cracked and causing my leaks. I also checked the lines going to the vac box that sits under the battery hold . that elbow was cracked as well.

You should be able to cap off the inlet/outlet under the intake and see if that changes the running.

Ray
Click to expand...
Thanks Ray, i'm going to check those 90 Degree elbows.

I replaced the line and checked the vacuum going to the box under the battery tray and it held vacuum... time to get out the carb cleaner again and inspect and spray the engine.
 
Is that line supposed to hold to vacuum? Has anyone had this problem and trouble shoot it?
Click to expand...
See above, but yes it should hold vacuum
Is the purge solenoid valve or the lines known to go bad not able to hold vacuum?
Click to expand...
Yes, and it usually ends up with an EVAP code
Can I cap this off at the intake to see it runs better?
Click to expand...
Yup, that is a great test and will not hurt anything but might set an EVAP code, depending on the engine temperature and fuel level, as those two parameters are used by the computer to test the EVAP system. If you want you can make sure you are below 20% or above 80% on the fuel gauge or the engine is at or near operating temperature, as the system will not test and no EVAP code will be set (if one does get set it will go away on the next test cycle)
 
my hose/elbow to the vacuum reservoir under the battery is cracked. does anyone have a link to buying a new hose? 2002 wrangler tj 4.0
 
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