Engine - Rough Idle/Poor Performance/Economy

90ford03

^ IDLE - ROUGH - 7.5L EFI - F-53 MOTORHOME CHASSIS

^ POOR FUEL ECONOMY - 7.5L EFI - F-53 MOTORHOME CHASSIS

^ POOR PERFORMANCE AT SLIGHT TO MODERATE THROTTLE - 7.5L EFI - F-53 MOTORHOME CHASSIS

Article No. 90-3-11

LIGHT TRUCK: 1989 F SUPER DUTY STRIPPED F53

ISSUE: Rough idle, poor performance at slight to moderate throttle, or poor fuel economy may be caused by an open map sensor line. This can occur if the nylon map sensor line contacts the EGR valve or EGR supply tube and melts a hole in the line. If the map sensor line is open to the atmosphere, the map sensor will no longer receive manifold vacuum pressure and the engine will run rich in all modes except wide open throttle.

ACTION: Inspect and, if necessary, repair and reroute the map sensor line. Refer to the following procedure for service details.

Figure 1:

1. Examine the map sensor line and inspect for damage, especially near the 90~ connector, Figure 1.

2. If damaged, disconnect the rearward end of the damaged map sensor line from the upper intake manifold 90~ connector.

3. Cut off the damaged portion of the map sensor line about 1" from the 90~ bend in the line.

NOTE: KEEP THE 90~ BEND IN THE LINE. DO NOT CUT IT OFF.

4. Install 19.5" (49.5 cm) of insulator tubing over the remaining map sensor line.

5. Install the 3/16" x 3/16" connector where the map sensor line was originally installed in the 90~ connector, Figure 1.

6. Install the 3" section of the 5/32" vacuum tubing on the connector.

7. Press the cut end of the remaining map sensor line into the 3" section of the vacuum tubing. Make sure to route the line across the top of the engine, above the oil filler tube and below the fresh air tube for the PCV system, Figure 1.

8. Position the insulating tubing to where it contacts the 90~ connector.

9. Secure the tubing assembly to the throttle position sensor with a bundling strap, while gently pulling the tubing assembly toward the front of the engine.

10. Cut off the excess bundling strap material flush with the retaining eye.

PART NUMBER PART NAME CLASS

383003-S Vacuum Tubing Connector AG
DOPZ-12226-B 5/32" Vacuum Tubing (50 Ft. AG
Roll)
C8WZ-9865-B Fabric Insulator Tubing BM
95874-S Bundling Strap AG

OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Eligible Under Basic Warranty Coverage, Emissions Warranty Coverage
OPERATION DESCRIPTION TIME
900311A Reroute MAP Line 0.5 Hr.
DEALER CODING
BASIC PART NO. CONDITION CODE
9E498 27
OASIS CODES: 620800, 630401, 640200