Engine Vacuum System - Starting/Driveability Problems

86ford18 Article No. 86-9-11

NO START - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


SLOW START (FLOODS HOT) - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


BACKFIRE ON DECEL - ALL EEC IV
- VACUUM SYSTEM DIAGNOSTIC PROCEDURES


IDLE ROUGH - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


LACKS POWER ON ACCELERATION
- ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


STUMBLES - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


SPARK KNOCK - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


M.P.G. POOR - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


ODOR - ROTTEN EGG - ALL EEC IV - VACUUM SYSTEM DIAGNOSTIC PROCEDURES


ENGINE OVERHEAT - ALL EEC IV
- VACUUM SYSTEM DIAGNOSTIC PROCEDURES
FORD 1983-86 ESCORT, EXP, MUSTANG, THUNDERBIRD, LTD, CROWN VICTORIA; 1984-86 TEMPO

LINCOLN-MERCURY 1983 LN7; 1983-86 LYNX, CAPRI, COUGAR, MARQUIS, GRAND MARQUIS, CONTINENTAL, MARK VII, TOWN CAR; 1984-86 TOPAZ

LIGHT TRUCK 1983-86 BRONCO II, RANGER; 1984-86 F, E AND BRONCO

CALIBRATIONS: All with EEC IV

All of the listed drive concerns can be caused by leaks and/or restrictions in the EEC vacuum systems.

This article describes procedures for diagnosing and servicing the vacuum control systems on vehicles with EEC (electronic engine control) systems.

If Service Codes are present, use "H" Shop Manual Procedures to correct the concern.

A leak or restriction in the vacuum system often results in a code 11 from a key-on/engine-off self test.

A leak or restriction in the vacuum system may cause a service code 22 during the engine running self test.

Visual Inspection:

1. Look for disconnected/loose hoses at vacuum sources and at termination such as sensors and actuators (for example: MAP sensor, EGR valve, TAB/TAD solenoid, etc.).

2. Eliminate any tight bends or kinks in vacuum lines.

3. Carefully check for breaks/cracks/splits or holes in plastic tees or elbows.

Eliminate Plugged or Obstructed Vacuum Lines:

1. Disconnect suspect vacuum line from its vacuum source and from its termination points.

2. Cover end of line with a clean white cloth to catch debris to determine if any foreign substance such as water, fuel, grease, etc. is emitted from the line.

3. Apply shop air to the vacuum line from the vacuum source side.

4. If any substance appears, determine cause, correct condition and replace components or vacuum lines as required.
5. Vacuum lines will sometimes collapse only when very hot due to high under hood temperatures. It is helpful to quickly inspect hoses after engine has been idled with closed until very hot.

Perform Leakdown Test on Vacuum Lines:

1. With hand vacuum pump, Rotunda Number 021- 00014, apply vacuum to each vacuum operated component through its vacuum line from the vacuum source end.

2. The applied vacuum should hold for a period of twenty seconds or more without significant loss.

3. If a vacuum loss occurs, determine cause and repair or replace component or vacuum line as required.

Additional techniques for isolating vacuum system faults are described in the Technician's Reference Book, "How to Read and Understand Vacuum Diagrams" (Vacuum System Diagnosis section).

OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY"