Engine - Surge On Light Acceleration/Idle Roll

Article No.
91-2-11
January 23, 1991


^ IDLE - 200-400 RPM ROLL BETWEEN 900-1400 RPM - 5.0L WITH E40D TRANSMISSION

^ SURGE - MODERATE TO HEAVY DURING LIGHT ACCELERATION - 5.0L WITH E40D TRANSMISSION CALIFORNIA UNITS AND HIGH ALTITUDE UNITS EXCEPT ECONOLINE

LIGHT TRUCK:
1990 BRONCO, ECONOLINE, F-150, F-250



CALIBRATION:
1-54P-R05, 1-54X-R05

ISSUE:
A moderate to heavy surge during light acceleration, may be caused by excessive EGR flow. The surge occurs between 900-1400 engine rpm and can be further described as a 200-400 rpm idle roll. The affected units are:

^ 1990 Econoline California calibration - 5.0L with an E40D transmission

^ 1990 Bronco California calibration - 5.0L with an E40D transmission

^ 1990 F-Series California calibration - 5.0L with an E40D transmission

^ 1990 Bronco high altitude calibration - 5.0L with an E40D transmission

^ 1990 F-Series high altitude calibration - 5.0L with an E40D transmission

ACTION:
Use the following diagnostic procedure to determine if a new EEC IV processor is required. The new processor has revised operating strategy.


1. Warm the engine to normal operating temperature.

2. Set the parking brake.

3. Firmly press on the service brake pedal.

4. Place the transmission in "DRIVE".

5. Increase the engine speed to 900 rpm.

6. Continue to increase the engine speed in increments of 100 rpm up to 1400 rpm.

7. Hold each engine speed for about five (5) seconds and note any variation in rpm.


NOTE:
A RPM ROLL OF 200-400 RPM IS TYPICAL ON THE PROBLEM UNITS.

8. Re-test with the EGR vacuum supply disconnected and plugged to see if the surge is gone.

9. If the surge is gone, install a new EEC IV processor.









Obtain an Authorized Modifications Decal and list the date, dealer number, and summary of alterations performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.

PART NUMBER PART NAME CLASS

FOPZ-12A650-DA EEC IV Processor - California W
FOPZ-12A650-EA EEC IV Processor - High B
Altitude



OTHER APPLICABLE ARTICLES:
None

WARRANTY STATUS:
Eligible Under Basic Warranty Coverage

OPERATION DESCRIPTION TIME
910213A Install EEC IV Processor - 0.9 Hr.
Econoline
910213A Install EEC IV Processor - 0.6 Hr.
F Series, Bronco

DEALER CODING
BASIC PART NO. CONDITION CODE
DRIVE M3

OASIS CODES:
612000, 612500, 618400