Engine - Spark Knock Diagnostic Procedure
Article No.93-13-10
06/23/93
SPARK KNOCK - SERVICE BAY DIAGNOSTIC SYSTEM PROCEDURE - THICK FILM IGNITION SYSTEM (TFI) - 1985-93 VEHICLES WITH 5.0L EFI ENGINES AND 1988-93 5.8L EFI ENGINES
LIGHT TRUCK:
1985-93 BRONCO, ECONOLINE, F-150-350 SERIES
ISSUE:
Spark knock may be caused by variability in ignition PIP (Profile Ignition Pick-up) output due to a combination of engine torsional vibrations and distributor electrical characteristics. A spark advance spike is generated which repeats every eight firings.
ACTION:
Perform the following Service Bay Diagnostic System procedure and, if necessary, replace the distributor.
NOTE:
THE FOLLOWING SBDS PROCEDURE MUST BE USED TO VERIFY IF THE SPECIFIED CONDITION EXISTS ON A GIVEN EFI/TFI 5.0L/5.8L ENGINE. DISTRIBUTORS ON ENGINES THAT HAVE A DETONATION CONCERN AND THAT DO NOT PASS THE SBDS TEST MUST BE RETURNED THROUGH WARRANTY WITH A "BEFORE AND AFTER" PRINTOUT OF THE SBDS IGNITION GRAPH (WITH THE SPIKING CLEARLY SHOWN) TO QUALIFY FOR REIMBURSEMENT.
SERVICE BAY DIAGNOSTIC SYSTEM PROCEDURE
1. Use SBDS 60 pin roadtest monitor/record. Select parameters PIP and Spout.
2. Start the warm engine and idle for at least two (2) minutes to allow EEC IV to learn and correct for normal PIP variance.
a. Record data using PVA pendant.
b. Store the data in a buffer.
3. Upload the data to the Cart and go to the playback graph mode.
4. Select Digital PIP and analog spark. Move the cursor to the smoothest (least noise) section of the spark curve, Figure 1.
5. Zoom in on the recording as much as possible. Look for timing spikes that REPEAT EVERY EIGHTH FIRING OF THE DIGITAL PIP SIGNAL, Figure 2.
6. Move the cursor across all spikes to read the timing difference.
NOTE:
THE SPARK ADVANCE WILL SPIKE UPWARD AT LEAST 20 ON SUSPECT VEHICLES.
7. Print the graph for warranty use.
^ Downward spikes would indicate a retarded spark condition and will NOT cause detonation.
^ Graphs without spikes (Figure 3) indicate that the distributor is NOT to be replaced.
8. If spiking is found, replace the distributor with the appropriate 12127 assembly. Refer to the Dealer Master Parts Catalog for correct parts usage.
a. Reuse the TFI module, cap and rotor.
b. Rerun the procedure and PRINT THE NEW GRAPH to verify that the new distributor corrected the spark knock condition.
c. Do not disassemble or rebuild the old distributor.
d. Return the distributor with the "before and after" graphs to the Warranty Parts Return Center.
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS:
Eligible Under Bumper To Bumper Warranty Coverage For 1992/93 Models, Basic Warranty For All Other Model Years And Emission Warranty Coverage
OPERATION DESCRIPTION TIME
931310A 1985-93 5.0L (EFI/TFI) 1.5 Hrs.
1988-93 5.8L (EFI/TFI) Bronco
and F-Series
931310B 1985-93 5.0L (EFI/TFI) 1.6 Hrs.
1988-93 5.8L (EFI/TFI) Econoline
DEALER CODING
BASIC PART NO. CONDITION CODE
12127 08
OASIS CODES: 615000, 615500, 615600