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Discussion Starter #1 (Edited)
89 caravan
born with t1 mitsu
replaced mitsu with garrett t1

both of these turbos were overboosting... the garrett is a fresh rebuild and the tech set the wastegate to open at 9 psi and fully open at 15 psi... the mitsu i thought was bad... but after this new install i am leaning another way that it is not that my turbos are bad but rather something else... i have added an aftermarket boost guage and the boost rises to 6psi and cuts out into overboost... plz help :bang head
 

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Stock controller will not hit overboost shutdown until it see's over 14.5 lbs of boost.
The only reason the turbo itself would cause an overboost issue is if the wastegate is not opening or in the case of the Mitsu and Garrett VNT which are small turbo's you lessen exhaust backpressure and the turbine side overspools causing boost creep at higher rpm's.

Boost levels are read by the controller from Map Sensor Voltage output.

You need to verify the vacuum system is correct.
The T-1 and T-2 use different vacuum routing.

You need to verify Map output = vacuum/pressure and that the actual pressure seen by the Map is what you are seeing on your boost gauge.

You need to verify actual pressure from the wastegate solenoid to turbo by teeing in a Vacuum/Pressure gauge.

You need to verify that the wastegate is actually opening at the correct pressure.
You can do that with a handheld vacuum/pressure pump.

CHECKING MAP SENSOR
http://www.turbododge.com/forums/f4/f14/344296-code-13-diagnostics.html

HANDHELD VACUUM/PRESSURE PUMP
Save on MityVac MV8500 at ToolTopia.com

VACUUM/PRESSURE GAUGE
(The gauge at Advance/Autozone only reads to 10 PSI so it will not help you)
Super price on KD Tools 2521 at ToolTopia.com

89 TURBO 1


89 TURBO 2
 

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Discussion Starter #5
after some detail inspection i found my boost gauge line had a kink in it. turbo does cut off at 14 lbs. i have ordered the tester gauge from tooltopia and am in waiting. also lookin at the vac/pressure lines... there is a line that comes from the airbox (larger of the 2 lines that are facing the front of vehicle)that t's off to 2 lines. one goes to brake booster and other is now plugged. mechanic i hired to change the turbo's out did not tell me about this line being plugged or what it went to:shrug:. how can i fix it to work properly or can this stay plugged with no issues? :shrug:
 

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an Overboost Fuel Cutoff should also set the ECM code...

I suggest running a vac line directly to turbo, bypassing the solenoid;
this should yield 'minimum boost' ..

if its still overboosting you need to re-adjust your wastegate / put a stock WG actuator back on
 

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Can you post a pic of the airbox and the line you are referring to?
Brake booster should be getting its vacuum from the rear of the intake manifold.
The line you are referring to may be for the cruise servo.
 

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Discussion Starter #8
Can you post a pic of the airbox and the line you are referring to?
Brake booster should be getting its vacuum from the rear of the intake manifold.
The line you are referring to may be for the cruise servo.
i have a stupid pic phone that i cant post to the web... if u would like i can send it to u phone to phone... send email of ur # and i will get it sent to u and mayb u could post it for me:dancing:
 

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If you check Naj's turbo 1 vac diagram you have to lines off the scroll side of compressor. One to waste gate one to airbox. I'm really not sure what the line to the airbox does but it's there for a reason. I have 2 lines going to the airbox on the tvan and one of them has a check valve on it, since I can't remember which I'm not much help!
 
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