Engine - Rough Idle

87ford10

IDLE - ROUGH - 4.9L Article No.
87-3-20

LIGHT TRUCK 1984-86 F-SERIES, BRONCO

ISSUE: A rough idle on F-Series and Bronco vehicles equipped with a 4.9L engine may be caused by variations within vehicle calibration limits.

ACTION: To correct this, perform the following service diagnostic procedure.

1. For 1985 vehicles built between August and November of 1984, install engine supports with a softer rubber compound. Also check the rear support (transmission support). If the color code of the rear support is yellow, replace it also.

2. Check the metal strap at the rear support (transmission support).

a. When the strap is installed correctly, it will go through the middle of the support and will not touch either edge.

b. When it has been installed incorrectly, it will bind (ground out) against the lower rubber/metal edge of the support. Remove the rear support and reposition the strap. Thread it through the slotted opening in the bottom of the support and rotate it 180 degrees.

3. Perform the STAR Test and check that code 11 is present on Key-On/Engine-Off (KOEO), KeyOn/Engine-Run (KOER), and Continuous Memory. If codes are present, then diagnose and repair as necessary before proceeding.

NOTE: On 1984 model vehicles built between Job #1 and 01/15/84, code 23 may be present in KOEO and KOER. If this is the case, refer to TSB 84-17-19.

4. Check initial timing:

a. 1984 F-Series and Bronco - All calibrations 10~ BTDC unless TSB 84-15-17 was previously performed. (Refer to TSB 84-15-17).

b. 1985 F-Series and Bronco - All calibrations 10~ BTDC except:
^ 4-52G-R10 - 12~C BTDC
^ 4-52S-R10 - 14~C BTDC

c. 1986 F-Series and Bronco -All calibrations 10~ BTDC.

5. Perform the following checks and adjustments on the carburetor:

a. Bring engine to normal operating temperature.

b. Run engine for about 20 seconds then turn ignition key to off.

c. An audible tapping should be heard from feedback solenoid. If not, service solenoid as required.

d. Remove carburetor.

e. Carefully remove air horn from carburetor.

f. Inspect fuel inlet needle for excessive wear. If needle tip is worn or is made of viton (black in color), perform TSB 84-17-13.

g. Inspect brass float. Replace if damaged/eroded or contains fuel. Set tapered brass floats to 0.810 inches whether replaced or not.

h. Reinstall the air horn.

i. Remove the tamper-proof cap which protects the idle mixture screw.

j. Remove the tamper-proof cap which protects the anti-diesel screw.

k. Reinstall the carburetor onto the engine.

l. Check and replace fuel filter if plugged or dirty.

m. Clean air cleaner tray and replace element if dirty.

n. Reset the anti-diesel RPM to a maximum of 450-500 RPM. Refer to TSB 84-7-13 for the anti-diesel screw setting procedure.

o. Install a new tamper-proof cap on the antidiesel screw.

p. Set the idle mixture to a preferred setting of 10 RPM drop using the propane enrichment method. Refer to the 1985 Shop Manual, Volume H, Section 4-132.

q. Reconnect the spout wire if disconnected.

r. Install a new tamper-proof cap on the idle mixture screw.
6. Remove and re-gap the spark plugs (BSF42) to 0.054.

7. Road test the vehicle and check that idle quality has improved.

8. If idle quality is still not up to the customer satisfaction, install the high energy CD Multi Spark Discharge ignition module (E4TZ- 12A199-A).

a. The module should be installed on R.H. fender liner behind battery.

b. Attach module at all four corners using rubber cushions provided. Reroute EEC IV harness away from module.

c. Attach the heavy gauge black wire to stud which holds coil bracket to side of engine. Route this wire under heater hoses and up over valve cover.

d. Connect heavy gauge red wire to starter relay on the battery side.

e. Reroute the CD harness under heater hoses and up over valve cover.

f. Unplug the EEC IV harness from the "E" core coil and plug it into the female end of the CD ignition module harness. Then plug the male end of the CD ignition module harness into the "E" core coil.

9. If the vehicle is equipped with a factory dash tachometer, check to make sure that it operates. If it does not operate:

a. Remove the gauge cluster.

b. Remove the plastic back from tachometer by removing the four nuts and two phillips head screws at rear of tachometer.
c. At top of circuit board, locate the 12K-ohm resistor which is slightly down and left of the number (750602-073).

d. Clip wire at right side of this resistor and rotate it slightly counterclockwise so that it no longer is connected.

e. Reinstall the plastic back cover onto tachometer.

f. Install tachometer into gauge cluster.

g. Install gauge cluster back into instrument panel.

PART NUMBER PART NAME CLASS

E5TZ-6038-U Engine Support - L.H. A
E5TZ-6038-T Engine Support - R.H. A
E0TZ-6068-B Transmission Support A
E4TZ-12A199-A Ignition Module C

OTHER APPLICABLE ARTICLES: 84-7-13, 84-15-17, 84-17-13, 84-17-19, 85-1-23
WARRANTY STATUS: Reimbursable within the provisions of the Warranty and Policy Manual
OPERATION: SP870320A - Step 1
TIME: 0.5 Hr. - Both front engine supports
OPERATION: SP870320B - Step 1
TIME: 0.6 Hr. - Rear engine support
OPERATION: SP870320C - Step 2
TIME: 0.5 Hr.
OPERATION: SP870320D - Steps 3-7
TIME: 2.9 Hrs.
OPERATION: SP870320E - Step 8
TIME: 0.4 Hr.
OPERATION: SP870320F - Step 9
TIME: 0.6 Hr. DLR. CODING: Basic Part No. DRIVE - Code: L4