Induction System Leak

Air induction system leaks can make the entire engine run too lean. This condition will be most apparent at idle, causing rough idle and/or stalling at idle. This may also result in Self-Test Code 41 and 91 (system always lean). Tests to locate induction system leaks, use propane.

1. Visually inspect all flange joints for indications of leaks.
2. Connect an EEC-IV Tester to read the rich/lean state of the EGO sensors.
3. Bring engine to normal operating temperature.
4. With engine idling in Neutral or Park and parking brake engaged, spray small amounts of propane around the following possible sources of air leaks:
   • Flange joint at rear of supercharger.
   • Bypass hose connections at rear of supercharger.
   • Flange joint at supercharger outlet adapter.
   • Four Tube which joints at supercharger outlet to upper tube, upper intercooler inlet, lower intercooler inlet, intake manifold adapter inlet.
   • Intake manifold adapter to intake manifold flange.
5. When propane is sprayed near an induction system air leak, the EGO monitor box will indicate "RICH" for one or two seconds, then return to normal switching. When the propane is removed from the leak, the EGO monitor box will indicate "LEAN" after one or two seconds.
6. If a leak is found, retighten the nuts at all tube flange locations and the supercharger outlet adapter "collar". See MINI-SEALING PROCEDURE below.
7. If a leak is still present, the entire induction system must be disassembled. See REMOVAL & INSTALLATION in this article below. If no leak is found see appropriate TESTS W/CODES article in this section.