Timing should be checked at each tune-up. Timing isn't likely to change very much with electronic ignition. Always refer to Emission Control Sticker (tune-up sticker) in the engine compartment as a specification guide. The sticker information reflects running changes made by the manufacturer during production of the vehicle.
On Chrysler front wheel driver cars equipped 3.3L/3.8L (standard on the Imperial and Fifth Ave. and options on the New Yorker and Dynasty models) model vehicles equipped with DIS (direct ignition system), ignition timing is not adjustable. On 1990-92 Dodge Monaco and 1988-92 Eagle Premier equipped with 3.0L engines, ignition timing is also not adjustable.
A stroboscopic (dynamic) timing light must be used, because static lights are too inaccurate for emission controlled engines. There are three basic types of timing light available. The first is a simple neon bulb with two wire connections. One wire connects to the spark plug terminal and the other plugs into the end of the spark plug wire for the No. 1 cylinder, thus connecting the light in series with the spark plug. This type of light is pretty dim and must be held close to the timing marks to be seen. It has the advantage of low price. The second type operates from the car's battery; two alligator clips connect to the battery terminals, while an adapter enables a third clip to be connected to the No. 1 spark plug and wire. This type provides a bright flash which can be seen even in bright sunshine. The third type replaced the battery current with 110 volt house current.
Some timing lights have other features built into them, such as dwell meters or tachometers. These are nice, in that they reduce the tangle of wires under the hood when you're working, but may duplicate the functions of tools you already have. One worthwhile feature, which is becoming more of a necessity with higher voltage ignition systems, is an inductive pickup. The inductive pickup clamps around the No. 1 spark plug wire, sensing the surges of high voltage electricity as they are sent to the plug. The advantage is that no mechanical connection is inserted between the wire and the plug, which eliminates false signals to the timing light. A timing light with an inductive pickup should be used on electronic ignition systems.
For vehicles with throttle body or multi-port fuel injection, refer to Fuel System for additional information.
See Figures 1 and 2
Proper ignition timing is required to obtain optimum engine performance. The distributor must be correctly indexed to provide correct initial ignition timing.
- Warm the engine to normal operating temperature. Shut off the engine and connect the timing light to the No. 1 spark plug. Do not, under any circumstances, pierce a wire to hook up a light. If using a magnetic timing light, insert the pick-up probe into the open receptacle next to the timing scale window.
- Clean off the timing marks and mark the pulley or damper notch and the timing scale with white chalk or paint. The timing notch on the damper or pulley can be elusive. Bump the engine around with the starter or turn the crankshaft with a wrench on the front pulley bolt to get it to an accessible position.
- Start the engine and unplug the coolant temperature sensor electrical connector. The electric radiator fan will operate and the malfunction indicator lamp (instrument panel Check Engine light) will turn on after disconnecting the coolant sensor.
- Aim the timing light at the timing marks. Be careful not to touch the fan, which may appear to be standing still. Keep your clothes and hair, and the light's wire clear of the fan, belts, and pulleys. If the pulley or damper notch isn't aligned with the proper timing mark (see the Tune-up Specifications chart), the timing will have to be adjusted.
Top Dead Center (TDC) corresponds to 0°; Before Top Dead Center (BTDC or B) may be shown as BEFORE; After Top Dead Center (ATDC or A) may be shown as AFTER.
- Loosen the distributor base clamp locknut. You can buy special wrenches which will make this task easier. Turn the distributor slowly to adjust the timing, holding it by the body and not the cap. Turn the distributor in the direction of rotor rotation (found in the Firing Order illustrations) to retard, and against the direction to advance.
- Tighten the locknut. Check the timing, in case the distributor moved as you tightened it.
- Shut off the engine and disconnect the light. Reconnect the coolant temperature sensor connector. On 1988 and later models, some fault codes may be set. They can be cleared immediately only with a special test instrument. However, as the ignition is turned ON and OFF 50-100 times (some later model years may take less re-starts to clear codes) in normal use, they will automatically be cleared by the system.