- Intermittent Malfunctions
*** THIS PROCEDURE HAS BEEN UPDATED BY TSB #84-87, DATED 3/84
Some 1982, 1983 and 1984 El Camino's with 3.8L engines may experience a fuel milage problem or poor driveability and performance. If all functions are within specifications, and no trouble codes are stored, the condition may be a detonation sensor picking up noises from the engine or transmission which will retard the timing as much as 19 degrees. To determine if this condition is occurring the following diagnosis should be used.
Perform diagnostic circuit check to determine if any trouble codes are present. If any codes are present use of the appropriate diagnostic chart and correction is required before proceeding any further.
DIAGNOSIS WITH ALCL SCAN TOOL, (1982-1983) SINGLE BOARD ECM.
Drive the vehicle at normal city and highway speeds with the scan tool in the KNOCK RETARD mode, and monitor the degrees of retard. "0" degrees of retard should be seen on the scan tool (with no spark knock). If reading other than "0" degrees is seen on scan tool (up to 19 degrees) and no spark knock is present, disconnect the detonation sensor, and road test the vehicle again at the same speeds as before. If no retard is being seen on the scan tool now, the detonation sensor is picking up noise from the engine or transmission .
DIAGNOSIS WITH ALCL SCAN TOOL, (1984).
If a 1984 equipped with a 3.8L engine is experiencing the same conditions a different reading will be displayed on the SCAN TOOL. The readings are no longer direct degrees of retard and are best explained as counts. Figures or counts as displayed on the scanner will be anywhere from 0 to 255. If the scan tool stays consistant (the same number) then the engine has 0 degrees of spark retard. However, if the numbers seen are continually increasing, for example (60,90,118,150,195,230) this indicates the timing is changing in large amounts, up to (19 degrees) which will usually set a code and is most likely an electrical disconnect from from or to the ESC module. Small number increases indicate smaller or very little spark retard is taken place.
To locate the noise causing spark retard, the vehicle should be run on a lift at the speed the most count changes were seen, and listen closely from underneath to the engine and transmission for any unusually loud knocks, pecks, or buzzing such as rocker arms, lifters or transmission front pump pressure regulator.
If retard is still seen with the knock sensor disconnected, retard is do to a false signal on a wire from knock sensor to controller or ESC connections. Rerouting wire away from other wires such as spark plug wires etc, is required.
DIAGNOSIS WITHOUT ALCL SCAN TOOL.
Perform diagnostic circuit check to determine if any trouble codes are present. If any codes are present use of the appropriate diagnostic chart and correction is required before proceeding any further.
If no trouble codes are present, drive the vehicle to determine if a performance condition exist (compare with another known good vehicle if necessary). If a driveability condition does exist, code 43 trouble code test chart should be used first. If no trouble code is found using the the code chart 43, disconnect the detonator sensor and drive the vehicle again. If improvement is noticed the problem could be noise being picked up by the detonation sensor from the engine or transmission.
To locate the noise causing spark retard, the vehicle should be run on a lift at the speed the performance was at it's worse, and listen closely from underneath to the engine and transmission for any unusually loud knocks, pecks, or buzzing such as rocker arms, lifters or transmission front pump pressure regulator.
If performance condition still exist with the knock sensor disconnected, retard is do to a false signal on a wire from knock sensor to controller or ESC connections. Rerouting wire away from other wires such as spark plug wires etc, is required.
The following components should be checked also:
1. Distributor shaft end play
2. Camshaft Timing
3. Spark plug wires and distributor cap.
*** THIS PROCEDURE HAS BEEN UPDATED BY TSB #84-65, DATED 2/84
Some 1982, 1983 or early 1984 models with a 3.8L engine may experience a harsh shake or rough idle at normal idle conditions, A/C on or off. This condition may be caused by grounded engine mounts which can be corrected by installing a shim, P/N 14082881, between the LH. engine mount and the block and using three longer bolts, P/N 435611. If the drive idle shake is improved, but not to an acceptable level, 6mm of shims should be installed between the R.H mount and the block.
*** THIS PROCEDURE HAS BEEN UPDATED BY TSB #86-254-6E, DATED 10/87
Some four port canister control valves have been replaced as a result of fuel found in the valve or the carb float bowl vent line. The presence of fuel found in this area does not mean that the valve is bad. To check valve follow procedures below.
1. Remove the hose connected to the control vacuum port (small top port) on the canister control valve.
2. Connect a hand vacuum pump to the port and apply 15" Hg of vacuum. If the diaphragm holds vacuum for at least 20 seconds, reconnect the hose and proceed to step 3. If the valve fails to hold vacuum replace the valve.
3. Start the engine and warn it up to operating temperature.
4. Disconnect the carb bowl vent line at the canister control valve and connect a hand vacuum pump to the carb bowl line port on the valve. Allow the engine to continue to run for 30 seconds and observe if vacuum builds up on the gauge. If so replace the valve.
5. With the engine still running and the vacuum pump still connected, apply 5" Hg vacuum and observe the gauge. If the valve does not hold vacuum for at least 20 seconds, replace the valve. Otherwise the valve is functional.
*** THIS PROCEDURE HAS BEEN UPDATED BY TSB #88-138-6D, DATED 2/88
During the diagnosis for an engine misfire, hesitation or roughness a spark plug or spark plug wire should be suspected because several types of commercial and homemade diagnostic equipment require the secondary ignition boots or wires to be pierced. Similarly, the use of pliers or other such tools to disengage a spark plug boot may pierce or damage the boot or wire. When this condition exist the current flow in the wire will increase to compensate for the higher resistance caused by the piercing of the wire. Over time the wire may fail creating a plug misfire condition
*** THIS PROCEDURE HAS BEEN UPDATED BY TSB#86-B-79, DATED 5/86
Some 1982-86 vehicles equipped with a THM 700-R4 automatic transmission may experience a condition where the engine stops running or lugs when shifted from park/neutral to reverse or drive.
This condition may be a result of [1][2]torque converter clutch engagement when either gear is selected, and may be caused by improper operation of the converter clutch valve, located in the pump cover.
If this condition exist, inspect the converter clutch apply valve for the following.
1. Not properly seated or missing retaining ring. When installing this retaining ring make certain the rounded edge of the retaining ring faces the valve stop.
2. Nicks or burrs in the converter clutch valve or valve bore.
3. Missing, broken or damaged converter clutch valve springs.
IMPORTANT: Prior to servicing the pump assembly for the above condition, make certain that the engine is properly tuned to specifications.
Intermittent malfunctions may occur which may or may not cause the "Check Engine" lamp to come on, or set trouble codes in the ECM memory. These intermittent conditions usually result in driveability complaints and cause trouble codes to be set in the ECM memory without turning on the indicator lamp, or are "read" as intermittent trouble codes when testing the system with the SCAN type tester. However, trouble code diagnosis charts cannot be used to diagnose this type of malfunction as a fault must be present in order to be located using the charts, and use of the charts to diagnose an intermittent condition may result in unnecessary replacement of components.
Most intermittent malfunction conditions are caused by poor electrical or vacuum hose connections, or defective or mis-routed wiring or hoses. The cause for most intermittent malfunctions can usually be located by performing a thorough visual inspection of the system vacuum and wiring harnesses and/or by road testing the vehicle while monitoring the suspected circuit with suitable test equipment. After performing the "Diagnostic Circuit Check" and ensuring that the indicator lamp is operating and that no "hard" codes are set in the ECM memory, use the following procedure to locate intermittent malfunctions:
1. Inspect vacuum hoses for splits, kinks and proper connection, and ensure that hoses are routed properly.
2. Inspect carburetor and mounting for air or vacuum leaks and correct as needed.
3. Inspect secondary ignition wiring and replace any wires that are burned, cracked or broken.
4. Inspect engine compartment and emission control system wiring and repair or replace wiring that is broken chaffed or damaged.
5. Inspect electrical connectors noting the following:
a. Ensure that terminal is making proper contact with wire by removing terminal from connector and inspecting for proper crimping and broken wire strands.
b. Ensure that all terminals are fully seated in connector.
c. Ensure that connector terminals are not damaged or deformed, and carefully reform terminals in connectors of suspected circuits to increase spring tension.
d. Ensure that connector halves are properly mated and fully seated.
6. Inspect indicator lamp and ALCL connector wiring for shorts to ground and repair as needed.
7. Check continuity between terminals A and U of ECM connector and engine ground, and repair wiring if no continuity exists.
8. Check for electrical interference caused by defective relays, ECM driven solenoids or switches, and secondary ignition system components, as they may cause voltage surges.
9. Ensure that EST wiring is properly routed and insulated from distributor wiring, distributor, ignition coil and alternator. Ensure that wire from ECM terminal 13 to distributor is satisfactorily grounded.
10. Inspect added accessories such as lights, two-way radios etc. for proper installation, ensuring that no accessories are patched in to engine control system wiring.
11. Ensure that diodes and resistors installed across accessories such as the A/C compressor clutch are not open.
12. Connect SCAN tool following manufacturer's instructions, or connect suitable voltmeter to suspected circuit and road test vehicle, noting any abnormal readings and the conditions under which they occur. Abnormal readings indicate that the tested circuit may be cause for malfunction.