Fleetwood V8-252 4.1L VIN 8 FI (1983)
PROM - Programmable Read Only Memory: Customer Interest
Engine Controls - Unsteady Idle With A/C Clutch Engaged
Bulletin No.T
83-94
File In Group
6C
Number
64
Date
May '83
IDLE SPEED VARIES WITH A/C CLUTCH ENGAGEMENT - 1983 HT4100 VEHICLES
A revised PROM calibration has been released for 1983 HT4100-equipped vehicles to provide a more responsive idle speed control action, which
reduces idle speed variations caused by compressor clutch engagement. This condition may be described as (1) an idle shake or vibration, which occurs
as idle speed drops due to compressor clutch engagement, or (2) an increase (surge) in idle speed within the range controlled by the ISC as the ISC
compensates for the A/C compressor load.
Diagnose an unsteady idle speed condition on 1983 HT4100-equipped vehicles, which occurs only with the air conditioning on, as follows:
1.
Enter diagnostics and perform switch tests. The car must pass the drive and reverse switch tests (.7.3 and .7.4). Shift slowly and deliberately from
neutral to drive to neutral, looking for the change. A drive switch which is misadjusted, or does not engage until shifted into manual third, may not
be detected if the lever is forced quickly past drive into 3, 2, or 1.
2.
Verify that the vehicle passes switch test .8.0 (ECC compressor clutch input).
3.
Check throttle switch for intermittent operation using the status indicator light on the ECC panel. (With available force, the switch may be on the
edge of tripping.)
4.
Check parameter .1.3 to determine the generation of PROM present. If an earlier generation PROM (lower number parameter .1.3 PROM ID) is
present, replace it with the new generation PROM as shown below:
INK STAMP
SERVICE
PROM I.D.
PROM
ON PROM
PROM P/N
PARAMETER .1.3
C Federal
CTK
1226529
14
C California
CTL
1226530
24
C Export
CTM
1226531
33
C Altitude
CTW
1226538
123
C Swiss/Sweden
CTZ
1226541
34
E/K Federal
CTN
1226532
44
E/K Federal Digital
CTS
1226535
74
E/K California
CTP
1226533
54
E/K California Digital
CTT
1226536
84
E/K Altitude
CTX
1226539
153
E/K Altitude Digital
CTY
1226540
183
E/K Export
CTR
1226534
63
E/K Export Digital
CTU
1226537
93
E/K Swiss/Sweden
CUA
1226542
64
E/K Swiss/Sweden Digital
CUB
1226543
94