DIAGNOSTICS
SERVICE MANUAL NUMBER 24
Page 5G-44
90-861327--1 OCTOBER 1999
Chart A-8 (1 of 2): Idle Air Control (IAC) Functional Test
IDLE AIR
CONTROL
(IAC) VALVE
441 BRN OR BLU/WHT
442 RED OR BLU/BLK
443 YEL OR GRN/WHT
444 LT GRN/BLK
ECM
MEFI 1
MEFI 2
J2-28
J2-13
J2-14
J2-29
MEFI 3
J1-28
J1-12
J1-27
J1-11
CIRCUIT DESCRIPTION:
The ECM controls idle speed to a calibrated “desired” rpm based on sensor inputs and
actual engine rpm. The ECM uses four (4) circuits to move the Idle Air Control (IAC) valve.
The movement of the IAC valve varies the amount of air flow bypassing the throttle plates.
The ECM controls idle speed by determining the position of the IAC valve.
DIAGNOSTIC AIDS:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a
wire broken inside the insulation. Check for the following items:
•
Poor connection or damaged harness. Inspect the ECM harness and connectors for
improper mating, broken locks, improperly formed or damaged terminals, poor termi-
nal to wire connection, and damaged harness.
•
Check for vacuum leaks, disconnected or brittle vacuum hoses, cuts, etc. Examine
manifold and throttle body gaskets for proper seal. Check for cracked intake man-
ifold.
•
Check for poor connections, opens, or short to grounds in CKT’s 441, 442, 443, and
444. This may result in improper idle control.
•
An IAC valve which is “frozen” and will not respond to the ECM, a throttle stop screw
which has been tampered with, or a damaged throttle body or linkage may cause
improper idle.
Index
Содержание 305 CID (5.0L)
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Страница 142: ...MCM MODELS SERVICE MANUAL NUMBER 24 Page 2A 26 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 166: ...MIE MODELS SERVICE MANUAL NUMBER 24 Page 2B 24 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
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Страница 721: ...DIAGNOSTICS SERVICE MANUAL NUMBER 24 Page 5G 94 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 779: ...GENERAL SERVICE MANUAL NUMBER 24 Page 7A 6 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 803: ...COLLECTORS SERVICE MANUAL NUMBER 23 Page 7C 16 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 859: ...HURTH TRANSMISSIONS SERVICE MANUAL NUMBER 24 Page 8C 18 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...