Turbocharger - Erratic Operation/Overboost Operation
88pontiac01 Number 87-6(Gasoline)-82 Date 1/88Subject: ERRATIC TURBO AND TURBO OVERBOOST OPERATION
1987 2.0L OVERHEAD CAM L-4 ENGINE (VIN CODE M) IN SUNBIRD AND GRAND AM MODELS
Some 1987 Turbo L-4 vehicles may experience at times erratic turbo operation for two known conditions:
CONDITION 1:
Under wide-open throttle operation and at the 2-3 upshift on an automatic transmission, a temporary turbo overboost can occur. A code 31 "Service Engine Soon" light may be triggered if overboost lasts too long.
For the above specific driving overboost condition, the following proms will correct the condition.
Sunbird And Grand AM Automatic Trans. P/N 16120036
To insure correctness of the repair, refer to the code 31 diagnostic section and check other possible causes of code 31.
CONDITION 2:
Erratic turbo boost operation can also be caused by boost solenoid sticking or oil plugged lines (refer to code 31 diagnostics in the service manual). During engine operation, engine oil can deposit inside the boost solenoid lines and/or wastegate pressure line vent at the wastegate solenoid.
If the wastegate solenoid's foam air vent is oil soaked, then replace the solenoid assembly. In addition, the wastegate-to-solenoid pressure line should be disconnected at both ends and blown clear. The wastegate solenoid-to-throttle body vacuum line should also be disconnected at the solenoid end and blown clear toward the throttle body. This line cleaning prevents turbo overboost from reoccurring and solenoid valve failure.
Use applicable labor time and number.