Town Car V8-281 4.6L SOHC (1991)
Throttle Valve: Adjustments
Throttle Valve (TV) Control Linkage System (FI)
ADJUSTMENTS
Throttle Valve (TV) Control Linkage System
5.8L Carbureted Engines Only Service Adlustment Procedure
The Throttle Valve (TV) Control Linkage System consists ot the linkage lever on the carburetor, the transmission control rod assembly, and the external
TV control lever on the transmission.
The linkage lever follows the motion of the carburetor throttle lever and has an adjustment screw for limited linkage adjustment capability. The TV
control rod transmits motion between the linkage lever on the carburetor and the TV control lever on the transmission. It is adjusted to proper length
during initial assembly. The external TV control lever actuates the internal TV control mechanism which regulates the TV control pressure. The external
TV control lever motion is controlled by stops internal to the transmission at idle and wide-open throttle (WOT).
The TV control linkage is set to its proper length during initial assembly using the sliding trunnion block at the transmission end of the TV rontrol rod
assembly. Under normal circumstances it should not be necessary to alter this adjustment. Any required adjustment of the TV control linkage can
normally be acomplished using the adjustment screw on the linkage lever at the carburetor. Major linkage adjustment (sliding trunnion on rod) may only
be required after maintenance invilving the removal and / or replacement of the carburetor, TV control rod assembly, or the transmission. Minor linkage
adjustment (adjustment screw on linkage lever) may be required after installing a new main control assembly, or after idle speed adjustments greater than
50 rpm and to correct omptaints of poor transmission shift quality as outlined in following parts.
Minimum Idle Stop
When the linkage is correctly adjusted, the TV control lever on the transmission will be at its internal idle stop position (lever up as far as it will travel)
when the carburetor throttle lever is at its minimum idle stop. There will be a light contact force between the throttle lever and end of the linkage lever
adjustment screw. Due to flexibility in the linkage system, the linkage lever adjustment screw would have to be backed-out approximately three turns
before a gap between the screw and throttle lever could be detected.
At wide-open throttle (WOT), the TV control lever on the transmission may or may not be at its wide-open stop. The wide-open throttle position must
not be used as the reference point in adjusting linkage.
Linkage Adjustment-General Instructions
Before any engine TV linkage adjustment can be done, the throttle lever at the carburetor (or throttle body) must be positioned at its minimum idle stop.
Without DC Motor Idle Speed Control (ISC)
5.8L Carbureted Engine
Check/adjust the engine curb idle speed to specification. Refer to the Engine/Emissions Diagnosis manual tor procedures to adjust throttle solenoid
applications. Make sure the curb idle speed is set to specification with and without the throttle solenoid positioner (antidieseling solenoid) energized, if
so equipped.
2.
Shut engine off. Remove air cleaner.
3.
De-cam the fast idle cam on the carburetor so that the throttle lever is against the idle stop or throttle solenoid positioner stop.
Linkage Adjustment at Carburetor
