Another area to look at in addition to the MAP sensor:
Check the plastic vacuum line going from the top of turbo vane servo to the vacuum modulator located on the passenger side fender and make sure it does not have a hole or crack in the line or one of the connection hoses on each end.
Also make sure you have good vacuum feeding the turbo vacuum modulator controller.
Items 1 & 6 in the diagram:
There is also a vacuum solenoid next to the vacuum modulator that has been known to go bad and when this happens, it will not allow any vacuum to the modulator valve.
The solenoid can be safely bypassed for a test to rule it out!
There are several parts as identified in the diagram below:
#2. is a vacuum reservoir, it is a small vacuum tank to supply a backup or quick supply of vacuum to the modulator valve when called for.
#7. is a modulator valve, (big valve) it modulates vacuum to the turbo depending on input from the ECM (engine conditions)
#8. is a solenoid, (small valve) it simply is either open or closed depending on engine running or not. It tries to hold vacuum on the vacuum reservoir when the engine is shut off.
The vacuum solenoid #8 can be bypassed as well as the vacuum tank #2 for test purposes.
The modulator valve #7 should never be bypassed; if you do the turbo vanes would go to 100% all the time!
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Supporting Vendor and Moderator of LOST05 Jeep Liberty CRD Limited
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