Engine - Low End Knock Under Load

Article No.
93-2-10

01/18/93

^ ENGINE - 4.9L - ACCELERATOR BRACKET/CABLE GROUND OUT

^ NOISE - "LOW END KNOCK" - 4.0L - ACCELERATOR BRACKET/CABLE GROUND OUT

LIGHT TRUCK:
1987-93 BRONCO, ECONOLINE, F-150-350 SERIES

This TSB article is being republished in its entirety to include 1993 model year vehicles.

ISSUE:
A "low end knock" from the engine compartment may be heard in the passenger compartment while the vehicle is in gear and under load. This occurs in the 1200 to 1500 rpm range while the engine is hot or cold. This noise may be caused by the accelerator bracket/cable grounding out.

ACTION:
Install a tie strap around the accelerator cable housing to the takeoff for the distributor. Refer to the following procedure for service details.

1. Confirm that there is a "low end knock" heard in the passenger compartment.

a. On an automatic transmission equipped vehicle, WITH THE PARKING BRAKE ENGAGED and automatic transmission in DRIVE, brake torque to 1200 - 1500 RPM or until the "low end knock" is heard.

b. Lift the wheels off the ground or use wheel chocks (4X4 not engaged).

WARNING:
DO NOT STAND IN FRONT OF THE VEHICLE.

c. From the side of the vehicle, have another technician grab the accelerator bracket firmly with his hands. The "low end knock" heard in the cab should be eliminated.

d. On a manual transmission equipped vehicle, test drive the vehicle to confirm that the "low end knock" is present.





2. Install a tie strap (95873-S) around the accelerator cable housing to the takeoff for the distributor on the 14289 wiring harness, Figure 1.

NOTE:
THE TIE STRAP MUST BE SECURED TIGHTLY.

3. Drive the vehicle to verify that the "low end knock" is eliminated.

4. If the "low end knock" is NOT eliminated, check the following items for possible sources of the noise.

^ Clutch lines - Check to see if they are loose in the bracket.

^ Brake lines - Look for loose lines striking against the frame.

^ Automatic transmission dip stick tube - Check for interference with the thermactor downstream air tube.

^ EGR valves being noisy - Disconnect the vacuum supply to verify. Replace as needed.

^ Transmission and engine mounts - Loosen and retighten to specification to neutralize mounts.

^ Fuel lines - Confirm that they are not striking the rocker arm cover.

^ Protrusions on the piston head - Engine build dates of 1/90 through 12/90 - Disconnect the spout wire. If the noise changes, remove the cylinder head and check for protrusions or pimples on top of the piston. Remove protrusions if found.

PART NUMBER PART NAME CLASS

95873-S Tie Strap C

OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 92-13-17

WARRANTY STATUS:
Eligible Under Bumper To Bumper For 1992/93 Models, Basic Warranty Coverage For All Other Models

OPERATION DESCRIPTION TIME
930210A Econoline 0.7 Hrs.
930210A F 150-350/Bronco 0.6 Hrs.

DEALER CODING
BASIC PART NO. CONDITION CODE
9A758 79

OASIS CODES:
497000, 702000, 702100, 702300