Mustang V8-302 5.0L HO (1987)
Thermactor Air Bypass & Diverter Solenoid: Customer Interest
Engine - Rolling Idle
Article No. 90-12-7
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IDLE - ROLLING - 5.0L HO - THERMACTOR AIR DIVERTER VACUUM SOLENOID VALVE INOPERATIVE
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THERMACTOR SYSTEM - 5.0L HO - THERMACTOR AIR DIVERTER VACUUM SOLENOID VALVE - DIAGNOSIS AND
REPLACEMENT PROCEDURE
FORD:
1987-90 MUSTANG
This TSB is being republished in its entirety to include a separate TAD/TAB solenoid valves and bracket assembly for 1987 Mustangs.
ISSUE:
A rolling idle may be caused by a leaking thermactor air diverter (TAD) vacuum solenoid valve.
ACTION:
If service is required, use the following diagnosis and service procedure. Refer to the appropriate model year Engine/Emissions Diagnosis
Manual, Section 10 for service details for the thermactor system.
An EEC-IV Quick Test may indicate codes 41 and 91, or 44 and 94, or no codes at all. When this occurs, proceed as follows:
1.
Run the engine until its temperature is fully stabilized.
2.
Turn the engine off.
3.
Restart the engine.
4.
After waiting for the idle roll to occur, disconnect the vacuum hose at the thermactor diverter valve. Allow it to remain connected to the TAD
solenoid.
5.
Plug the vacuum hose.
6.
After an additional one (1) minute of engine running time, the rolling idle should stop.
Figure 1
7.
If this stops the rolling idle, install a new TAD vacuum solenoid valve on 1988-1990 Mustangs or a new TAD/TAB vacuum solenoid valves and
bracket assembly on 1987 Mustangs. These parts are located in the RH rear of the engine compartment, behind the shock tower, Figure 1.
