Component Tests and General Diagnostics

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

WARNING: The vehicle must be in a well ventilated area away from any source of spark or flame when using propane.

1. Visually inspect flange joints for indications of leaks.

2. Connect an EEC-IV Monitor Box (007-00018) or voltmeter to read the rich/lean state of the EGO sensors.

3. Bring engine to normal operating temperature.

4. With engine idling NEUTRAL (M/T) or PARK (A/T) and parking brake engaged, introduce 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.

^ The tube joints at:

- Supercharger outlet to upper tube.

- Upper intercooler inlet.

- Lower intercooler outlet.

- Intake manifold adapter inlet.

- Intake manifold adapter to intake manifold flange.

5. When propane is introduced near an induction system air leak, the EEC-IV Monitor Box or voltmeter will indicate "RICH" for one or two seconds, then return to normal switching. When the propane is removed from the leak, the EEC-IV Monitor Box or voltmeter will indicate "LEAN" after one or two seconds.

6. If a leak is indicated, verify nut torque at all tube flange locations and the supercharger outlet adapter collar.

7. If a leak is still present, the entire induction system must be disassembled and resealed.