SERVICE MANUAL UPDATE THROTTLE BODY INSTALLATION
Models 1989 FIREBIRD EQUIPPED WITH Affected: 2.8L V6 (VIN CODE S)
SERVICE MANUAL UPDATE
The throttle body installation procedure shown in the 1989 Service Manual Section 6E3-C2 contains incorrect information. If it becomes necessary to install a replacement throttle body, adjust TPS and minimum idle speed as follows:
NOTICE: o The minimum idle speed adjustment is critical to vehicle performance and component durability. Incorrect minimum idle speed adjustment (too high), will cause the IAC valve pintle to constantly bottom on its seat and result in early valve failure. If minimum idle speed is adjusted too low, the vehicle may not start in cold weather or may stall during warm-up.
o Minimum idle speed should only be adjusted when installing a replacement throttle body.
o The idle stop screw is used to regulate minimum idle speed of the engine. On original equipment throttle bodies, it is adjusted at the factory, then covered with a plug to discourage unnecessary readjustment.
Adjust
1. Block drive wheels, and apply parking brake.
2. Connect a "Scan" tool to the ALDL connector.
3. Turn ignition to "ON" position.
4. Select "TPS" voltage display on "Scan" tool, and adjust TPS to obtain 0.55 +/- 0.1 volt.
o Tighten attaching screws enough to hold TPS in place. Readjustment may be required following minimum idle speed adjustment.
5. Select "Field Service Mode" on "Scan" tool (refer to "Scan" tool instructions) . This will cause IAC valve pintle to seat in throttle body (closing air passage). Wait at least 45 seconds, disconnect IAC valve connector, then exit "Field Service Mode."
6. Place transmission in "Park" (A/T) or "Neutral" (M/T) . Start and run engine until it reaches normal operating temperature, and "Closed Loop" operation as read on the "Scan" tool.
o It may be necessary to hold throttle open slightly to maintain idle.
7. On vehicles equipped with automatic transmission, place gear selector in "Drive."
8. Select "Engine rpm" on "Scan" tool, and read engine speed:
Important
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o Engine should be at normal operating temperature and in "Closed Loop."
o Accessories (A/C, rear defog, etc.), and engine cooling fan should be "OFF."
o Make sure throttle and cruise control cables do not hold throttle open.
o Idle speed should be: 550 +/- 50 rpm in "Drive" (A/T) 650 +/- 50 rpm in "Neutral" (M/T)
9. Adjust minimum idle speed if necessary.
10. On vehicles equipped with automatic transmission, place gear selector in "Park."
11. Turn ignition "OFF."
12. Connect IAC valve electrical connector.
13. Turn ignition to "ON" position, and recheck TPS voltage on "Scan" tool. Adjust if necessary, to obtain 0.55 +/- 0.1 volt.
o Tighten TPS attaching screws to 2.0 N.m (18 lb. in.). Make sure adjustment did not change after tightening screws.
14. Turn ignition "OFF" for ten seconds (this will reset IAC valve pintle position).
15. Start engine and check for proper idle operation.
16. Disconnect "Scan" tool.
17. Remove block from drive wheels.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
