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 idle 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. For computer system information see Computers and Control Systems.

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

1. Visually inspect all flange joints for indications of leaks.

2. Connect an EEC-IV Monitor or voltmeter 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.

^ The 4 tube joints at,

a. Supercharger outlet to upper tube.

b. Upper intercooler inlet.

c. Lower intercooler outlet.

d. Intake manifold adapter inlet.

^ Intake manifold adapter to intake manifold flange.

5. When propane is sprayed near an induction system air leak, the EEC-IV Monitor 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 or voltmeter 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".

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