This DIY Haynes service, repair and maintenance manual, covers all 1969-1990 Chevrolet (full-size, rear-wheel drive) sedans and station wagons, including:

• Chevrolet Caprice
• Chevrolet Biscayne
• Chevrolet Bel Air
• Chevrolet Impala

All cars equipped with V6 and V8 engines. NOTE: this manual DOES NOT include diesel or front-wheel drive information.
Book Excerpt: 1969-1990 Chevrolet Caprice, Biscayne, Bel Air, Impala, Wagons Repair Manual TUNE-UP AND ROUTINE MAINTENANCE

AIR FILTER AND PCV FILTER REPLACEMENT
(Refer to illustrations 33.2, 33.4 and 33.7)

1. At the specified intervals, the air filter and (if equipped) PCV filter should be replaced with new ones. The engine air cleaner also supplies filtered air to the PCV system.
2. The filter is located on top of the carburetor and is replaced by unscrewing the wing nut from the top of the filter housing and lifting off the cover (see illustration).
3. While the top plate is off, be careful not to drop anything down into the carburetor or air cleaner assembly.
4. Lift the air filter element out of the housing (see illustration) and wipe out the inside of the air cleaner housing with a clean rag.
5. Place the new filter in the air cleaner housing. Make sure it seats properly in the bottom of the housing.
6. The PCV filter is also located inside the air cleaner housing on some models. Remove the top plate and air filter as previously described, then locate the PCV filter on the inside of the housing.
7. Remove the old filter (see illustration).
8. Install the new PCV filter and the new air filter.

EMISSIONS CONTROL SYSTEMS

ELECTRONIC SPARK CONTROL (ESC) SYSTEM GENERAL DESCRIPTION

1. Irregular octane levels in modern gasoline can cause detonation in an engine. Detonation is sometimes referred to as "spark knock".
2. The Electronic Spark Control (ESC) system is designed to retard spark timing up to 20-degrees to reduce spark knock in the engine. This allows the engine to use maximum spark advance to improve driveability and fuel economy.
3. The ESC module sends a voltage signal of 8 to 10-volts to the ECM when no spark knock is occurring and the ECM provides normal advance. When the knock sensor detects abnormal vibration (spark knock), the ESC module turns off the circuit to the ECM. The ECM then retards the EST distributor until spark knock is eliminated.
4. Failure of the ESC knock sensor or loss of ground at the ESC module will cause the signal to the ECM to remain high. This condition will result in the ECM controlling the EST as if no spark knock is occurring. Therefore, no retard will occur and spark knock may become severe under heavy engine load conditions. At this point, the ECM will set a Code 43. Loss of the ESC signal to the ECM will cause the ECM to constantly retard EST. This will result in sluggish performance and cause the ECM to set a Code 43.
CHECK
5. Connect a timing light to the engine according to the manufacturer's instructions. With the engine running at approximately 1500 rpm carefully tap on the engine block with a hammer near the knock sensor while monitoring the ignition timing with the light.

The timing should retard with each tap of the hammer. If it doesn't, disconnect the electrical connector to the knock sensor. Connect the lead of a 12-volt test light to the positive terminal of the battery and touch the terminal of the knock sensor harness connector with the tip of the test light while monitoring the ignition timing with the timing light. The timing should retard each time the terminal is touched with the test light. If it does, the knock sensor is defective. If timing still did not retard, the ESC module may be defective. Before replacing the ESC module, check the following wiring and connections at the ESC harness connector and repair as necessary.

Subject: 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990 Chevrolet Caprice, Biscayne, Bel Air, Impala, Wagons service, maintenance, repair. ISBN-10: 1850106363 |ISBN-13: 9781850106364 | Haynes 24045