Intake Manifold - Throttle Sensitive Induction Whistle
88pontiac01Number 87-6(Gasoline)-81 Date 1/88
Subject: THROTTLE SENSITIVE INDUCTION WHISTLE
1987 6000, GRAND AM, AND FIERO MODELS WITH 2.5L L4 ENGINE (VIN CODES R AND U)
The whistle-free geometry can be retrofitted into early manifolds on a vehicle, if needed, as follows:
1. Remove air cleaner and open throttle blade.
2. With a suitable light, inspect the throttle bore/idle air passage junction to see if it has the relief. If it does, then the whistle is due to loose hoses, air cleaner, or other cause.
3.. Remove TBI (Throttle Body Injector).
4. Put a clean rag into the intake manifold throttle bore to prevent aluminum filings from falling into the manifold.
5a. Use a 1/4 inch die grinder tool or equivalent to grind a relief
into the manifold.
b. File a notch into the idle air passage floor in the manifold per the Illustration.
c. Use a shop vacuum to draw aluminum filings away from manifold while grinding.
6 . Vacuum the entire area of rework when grinding is completed,
remove rag, and vacuum again. NOTE: IT IS VERY IMPORTANT THAT
FILINGS DO NOT GET INTO THE MANIFOLD.
7. Reinstall TBI with a new gasket, P/N 10066605.
8. Install air cleaner.
9. Road test vehicle to verify work. (When properly executed, this procedure has been 100% effective).