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Discussion Starter · #1 ·
my 88 turbo is not boosting, the apc gauge will go up to the yellow section and stop, i think that i can hear the turbo boosting, but there is no boost that actually builds, i checked the turbo houseing and the turbine spins freely, i also checked the bypass and it also functions. is there any thing i could be missing ik that the apc and wastegate also have control over the turbo system, but i do not know a good way to test either.
if anybody knows could you please give me your ideas
thanks
 

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Make sure that all the vac lines are still connected to the APC valve next to the coil to their respective places.
 

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Also, start simple, think coil, wires, vac leaks (as dan mentioned), and even the fuse for the apc (i think it's 10) If none of those are the culprit then think about the bigger things. More likely than not you have a vac leak.
 

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Discussion Starter · #4 ·
thanks guys, i checked and even replaced a few iffy vac hoses, theyre good now and it still does the same thing
 

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Make sure the arm from the wastegate actuator to the wastegate arm on the turbo is still connected.
 

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thanks guys, i checked and even replaced a few iffy vac hoses, theyre good now and it still does the same thing
I helped a friend who had similar symptoms as you describe. We had all the usual turbo, wastegate and intake checks. Might be worth a look.

It ended up being a clogged exhaust system. Either the cat had melted down or the muffler was full of debris it stopped the exhaust flow enough to prevent boost. He disconnected the down pipe aft of the elbow to test. Loud, but enough to trace down the problem.
 

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Discussion Starter · #8 ·
after performing tests on all vac lines even those to the heater in the dash, and testing the wastegate and the apc solenoid the turbo still isnt really the same, i found one more leaky vac hose while testing them with a mityvac, and cut the end off that was cracked, the car definitely feels peppier, but still is not boosting all the way it now gets about 1/4 into the yellow section of the apc/boost gauge on the dash. only problem is that is at 4500 rpm, much higher that it should, ecspecially since the fuel cut is at i think 550 rpm. i gues next would be a check for exhuast block, it has been rattleing more than usually ( exhaust that is) so somthing could've fallen apart
 

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Discussion Starter · #10 ·
yep, tested the wastegate, with mityvac, that is the wastegate moves and holds both vac and pressure, and there is not a preturbo leak, luckily the exhuast manifold in these cars are right up in front of you when you open the hood, but still the turbo will not spool until about 4500 rpm,
 

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Just because the wastegate actuator is holding vac/pressure doesn't mean that the wastegate is not leaking. If the lock nut on the adjustable arm loosens, the arm can actually unscrew over time and lengthen. In that case, the wastegate won't seal tightly enough. You may want to disconnect the arm at the wastegate, screw it so that it shortens to the point that you can almost not get it back on and then back it off 1/2-1 turn and reconnect it (be sure to snug down the lock nut). Unplug the wire from the APC solenoid and drive the car. You should only be able to run base boost at that point, but if it goes quickly to base boost and holds, you'll know that you had a leaky wastegate.
 
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