Turbocharger - Diagnosis Procedures
86subaru1NUMBER 02-50-86
DATE 11-07-86
APPLICABILITY:
1985 AND '86 VEHICLES WITH WATER COOLED TURBOCHARGERS
SUBJECT: TURBOCHARGER DIAGNOSIS
THIS SERVICE BULLETIN IS FOR INFORMATION ONLY
The following three symptoms are commonly associated with Turbocharger Diagnosis:
^ lack of engine power when accelerating
^ excessive engine oil consumption and/or white smoke exiting the tailpipe
^ noise in the engine compartment
NOTE: THESE SYMPTOMS MAY ALSO BE RELATED TO OTHER ENGINE MALFUNCTIONS.
To assist you with the inspection of the turbocharger operation follow this procedure.
^ LACK OF ENGINE POWER WHEN ACCELERATING
1) Check the waste gate operation by checking the turbo boost pressure while driving with the engine above 2800 RPM. The boost pressure should be 15.75 +/- 1.18 in.Hg. If not, check these inoperative waste gate symptoms:
A) Waste gate stuck open resulting in poor acceleration.
B) The waste gate does not open resulting in excessive pressure which activates the fuel cut system of the ECM. This will limit full throttle RPM to approximately 2,800 RPM.
NOTE: THE FUEL CUT SYSTEM OPERATES WHEN THE BOOST PRESSURE EXCEEDS 18.50 in.Hg.
C) Check for a disconnected, loose or split air intake hose.
D) Make sure there is no interference between the waste gate and the cover shield.
^ EXCESSIVE OIL CONSUMPTION AND/OR WHITE SMOKE EXITING THE TAILPIPE.
1) Perform an oil consumption test using the 1986 Subaru Service Manual, section 2-3, pages 49 & 50.
2) Check other related symptoms;
A) On vehicles with Automatic Transmissions check the vacuum modulator valve and line for fluid leakage.
B) Check for a leaking head gasket or cracks in the engine block and cylinder head resulting in anti-freeze entering the exhaust system. Perform a compression test, a cylinder leak down test and a cooling system pressure test using the 1986 Subaru Service Manual, section 2-3 subject "Engine Troubleshooting".
C) Check the fuel system for signs of contamination.
^ NOISE IN THE ENGINE COMPARTMENT
1) Check the following related symptoms:
A) Check the engine for other foreign mechanical noises.
B) Check the transmission for other foreign mechanical noises.
C) Check the accessories and the air conditioning compressor, if equipped for any irregular sounds.
If, after ensuring proper operation of all engine compartment related functions, and symptoms still persist remove the Turbocharger from the engine compartment and perform the following;
*A) Check the axial and radial turbine shaft movement.
Axial maximum freeplay is 0.0035 in. Radial maximum freeplay is 0.0067 in.
*B) Check the waste gate rod operation by applying 9 to 10 psi of
air pressure at the actuator and measuring the movement of the rod which should be approximately 0.79 in.
C) Check the actuator hose for looseness or cracks.
D) Check the turbine and compressor blades for damage.
E) Check for interference between the turbine and compressor blades and the casing.
F) Check the turbine and casing for oil wetness.
If the Turbocharger when removed does not pass the checklist above, replace it. If it does pass, reinstall and repeat the diagnosis.
*NOTE: SEE THE 1986 SUBARU SERVICE MANUAL SECTION 2-7, PAGES 64-66
UNDER "FUEL INJECTION" TURBOCHARGER SYSTEM, FOR MORE INFORMATION ON MEASURING THE TURBINE SHAFT AND THE WASTE GATE ACTUATOR ROD MOVEMENT.