How about these:
Q: My boost gauge doesnt show any boost, and my car has no power. Does this mean my turbo is bad?
A: It is possible for the turbo to be bad, but there are many other causes for little or no boost. Check all the hoses between the turbo outlet and the throttle body to be sure the clamps are tight, and the hoses dont have any rips or tears, or werent "folded over" on themselves last time they were reinstalled. Look for intake restrictions, such as a VAM to turbo hose that collapses, and exhaust restrictions, such as a plugged cat converter. You can test for exhaust restrictions by loosening the down pipe from the turbo outlet and driving the car to see if the lost power returns. Check your ignition timing. Also check your timing belt and valve timing to be sure the timing belt hasnt skipped a tooth.
If all these check out OK, remove the VAM to turbo hose, and the turbo inlet elbow so you can see and feel the compressor wheel. Reach in, and try to spin the compressor wheel. It should spin freely. Try to move the wheel up and down and side to side. You should be able to feel some play, but not much. Look at the blades to see if the edges are damaged from contact with the housing. If so, the turbo needs a rebuild. Push / pull in the wheel to feel for axial play. There should be almost none. If axial play is more than a few thousandths of an inch, a rebuild is in order.
Q: There is oil in the throttle body, turbo compressor housing, VAM, and intercooler. Does this mean my turbo is leaking oil and needs to be replaced?
A: It is normal for there to be a very light film of oil in these areas, but lots of oil (puddles) indicate a problem somewhere. The most common cause of excessive oil in the intake system is a leaky PCV valve allowing boost to pressurize the crankcase, which forces oil out through the oil seperator at the back of the valve cover, and down through the tube that connects the seperator to the turbo inlet. In severe cases, this can even cause the dipstick to blow out, and spray oil all over the engine compartment. Replace the PCV valve with ONLY THE FORD PART! The part number is EV127A. Clean out the oil seperator on the valve cover with brake cleaner. You may want to clean out the other oil seperator down on the block where the PCV hose enters the block also. Some people put a one way check valve in the hose between the PCV valve and the intake to positively eliminate this problem. Get a F3XY-2365-A 1993 Mercury Villager brake booster check valve for this purpose. It costs under $10 at and Ford or LM dealer.
The next most common cause of this problem is worn rings allowing excessive blow by, which will also pressurize the crankcase in much the same way a bad PCV valve does. A compression test may help diagnostics here, but a leakdown test will locate this problem for sure. Excessively worn intake valve guides and shot or missing valve stem seals can also leak boost from the intake into the crankcase, so you may want to have a look at those also.
If the above check out OK, it is time to pull off the turbo for inspection.
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Jeff Korn
88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
Jeff Korn
88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized