Skyhawk L4-121 2.0L Turbo VIN M FI (1987)
Throttle Valve Assembly: Technical Service Bulletins
A/T Throttle Valve - Summary of Conditions/Diagnosis
Bulletin 87-7-4
Date
Jan. '87
Ref. No. 87-062-7
SUBJECT:
SUMMARY OF THROTTLE VALVE (T.V.) SYSTEMRELATED CONDITIONS AND DIAGNOSIS
MODELS AFFECTED: ALL THM TRANSMISSIONS/TRANSAXLES (EXCEPT THM 350 AND 400)
Throttle valve (T.V.) pressure controls the shift pattern and the amount of hydraulic line pressure used to apply clutches and bands.(NOTE: The THM
440-T4 T.V. cable controls shift timing, not shift feel. Line pressure is not directly affected by T.V. cable setting.) If proper line pressure is not available,
excess slippage may occur during the shift. If the T.V. cable is tailored in an effort to modify shift pattern/feel, this misadjustment can result in
transmission/transaxle failure.
IMPORTANT:
Do not attempt to correct a condition by changing the T.V. cable setting from it's proper adjustment. Apparent improvements from T.V.
cable "tailoring" indicate a need for further diagnosis into the real cause of a condition (such as engine performance, the control valve,
governor or servo assemblies, etc.)
Dealer personnel and customers should know that certain types of heavy duty or high performance vehicles have transmissions calibrated to provide
crisp, firm shifts for durability/performance. Once again, the T.V. cable must not be tailored in an effort to modify shift pattern/feel on these applications.
IMPORTANT:
Make sure engine fuel, electrical and mechanical systems are performing properly before attempting transmission/transaxle diagnosis.
For example, a fouled fuel injector, cracked spark plug, damaged spark plug wire or vacuum leak can affect transmission/transaxle
performance.
The T.V. system may cause one or more of the following conditions:
-
Delay or harsh upshifts
-
Early and slipping upshifts
-
High or low line pressure (except the THM 440-T4 - No upshifts
-
Chatters on takeoff
-
1-2 shift at full throttle only
-
No full throttle or part throttle detent downshifts
-
Intermittent second gear starts
The listed conditions may be caused by a T.V. cable that is:
-
Improperly adjusted
-
Kinked or binding
-
Disconnected
-
Broken
-
Wrong part
CAUTION: To avoid possible personal injury and/or damage to the vehicle, the following diagnosis procedure must be performed with the vehicle
parking brake properly applied.
DIAGNOSIS
Inspect:
^
T.V. cable for correct part number, listed in the parts catalog.
^
T.V. cable for kinked, binding, disconnected or broken condition.
Install or Connect:
^
Line pressure gauge.
^
Engine tachometer.
^
Warm up engine to normal operating temperature.
^
Run engine at 1000 rpm.
^
With gear selector in "Park", note oil pressure. (NOTE: Remaining steps do not apply to the THM 180, 350, 400 or 440-T4. Refer to the
appropriate Service Manual for line pressure diagnosis procedures.)