Skip the auto shop - Our mechanics make house calls

How to Adjust Timing on a Car

spark plug being pulled out of an engine

Ignition timing refers to the ignition system that allows the spark plug to fire, or ignite, a few degrees before the piston reaches top dead center (TDC) on its compression stroke. In other words, ignition timing is the adjustment of the spark produced by the spark plugs in the ignition system.

When the piston travels to the top of the combustion chamber, the valves close and allow the engine to compress the mixture of air and fuel inside the combustion chamber. The ignition system's job is to ignite that air/fuel mixture to make a controlled explosion to allow the engine to rotate and produce power that can be used to move your vehicle. The ignition timing or spark is measured in the degrees the crankshaft is rotating, bringing the piston to the top of the combustion chamber, or TDC.

If the spark comes before the piston reaches the top of the combustion chamber, also known as advanced timing, the controlled explosion will work against the engine rotating and produce less power. If the spark comes after the piston starts traveling back down the cylinder, known as retarded timing, the pressure created when compressing the air/fuel mixture will dissipate and create a weak explosion, not allowing the engine to produce maximum power.

A good indicator that ignition timing may need to be adjusted is when the engine runs too lean (too much air, not enough fuel in the fuel mixture) or too rich (too much fuel and not enough air in the fuel mixture). These conditions are sometimes shown by the engine backfiring or pinging while accelerating.

Having the correct ignition timing will allow the engine to efficiently produce maximum power. The number of degrees will vary between manufacturers so it is best to check the service manual for your specific vehicle to determine exactly what degree to set your ignition timing.

Part 1 of 3: Locating timing marks

Materials Needed

  • Distributor wrench of the appropriate size
  • Free repair manuals ­ Autozone provides free online repair manuals for certain makes and models Autozone
  • Repair manuals (optional) Chilton

Older vehicles that have a distributor ignition system will have the ability to fine-tune ignition timing. Typically, timing will need to be adjusted due to the normal wear of moving parts in the ignition system. One degree may not be noticeable at idle, but at higher speeds this can cause the vehicle’s ignition system to fire a little early or late, which will decrease overall performance of the engine.

If your vehicle uses a distributorless ignition system such as coil on plug, timing cannot be adjusted as the computer makes these changes on the fly when necessary.

crankshaft pulley and timing cover with arrows pointing out the timing cover marks and crankshaft pulley mark

Step 1: Locate the crankshaft pulley. With the engine off, open the hood and locate the crankshaft pulley.

There will be a mark on the crankshaft pulley along with degree mark(s) on the timing cover.

  • Tip: These marks can be observed while the engine is running by illuminating this area with the timing light to check and adjust ignition timing.

pink clamp clamped around the spark plug wire for the number one cylinder

Step 2: Locate the number one cylinder. Most timing lights will have three clamps.

A positive/red and negative/black clamp is hooked up to the vehicle’s battery and a third clamp also known as the inductive clamp, clips around the number one cylinder’s spark plug wire.

  • Tip: If you do not know which cylinder is #1, consult the factory repair information for the firing order.

hand on distributor as if they were going to rotate it in one direction or the other

Step 3: Loosen the adjusting nut on your distributor. If ignition timing needs to be adjusted, loosen this nut enough to allow the distributor to rotate so timing can be advanced or retarded.

Part 2 of 3: Determining if adjustment is needed

Materials Needed

  • Distributor wrench of the appropriate size
  • Free repair manuals ­ Autozone provides free online repair manuals for certain makes and models Autozone
  • Repair manuals (optional) Chilton
  • Timing light

picture of instrument cluster with a green circle highlighting the temperature gauge showing engine is at normal operating temperature

Step 1: Warm up the engine. Start the engine and allow it to rise to an operating temperature of 195 degrees.

This is indicated with the temperature gauge needle reading in the middle of the gauge.

picture of timing light and its wiring showing where electrical wires are being attached

Step 2: Attach the timing light. Now is a good time to attach your timing light to the battery and number one spark plug and shine the timing light at the crankshaft pulley.

Compare your readings to the manufacturer's specifications in the factory repair manual. If the timing is out of spec, you will need to adjust it in order for the engine to run at maximum performance.

vacuum line being disconnected

  • Tip: If your vehicle has vacuum-assisted ignition timing, disconnect the vacuum line going into the distributor and plug the line with a small bolt to prevent a vacuum leak while the timing is being adjusted.

Part 3 of 3: Performing the adjustment

Materials Needed

  • Distributor wrench of the appropriate size
  • Free repair manuals Autozone provides free online repair manuals for certain makes and models Autozone
  • Repair manuals (optional) Chilton
  • Timing light

Step 1: Loosen the adjusting nut or bolt. Return to the adjusting nut or bolt on the distributor and loosen it enough to allow the distributor to rotate.

service connector with a jumper wire linking the two wires of the connector together with a hand holding the connector

  • Tip: Some vehicles require you to install a jumper wire on an electrical connector to short or break the connection with the vehicle’s computer so timing can be adjusted. If your vehicle has a computer, overlooking this step will prevent the computer from accepting the adjustments.

Step 2: Rotate the distributor. While using the timing light to look at the timing marks on the crank and timing cover, rotate the distributor to make the necessary adjustments.

  • Note: Each vehicle may vary, but a general rule of thumb is, if the rotor inside the distributor spins clockwise with the engine running, rotating the distributor counterclockwise will advance ignition timing. Rotating the distributor clockwise will perform the opposite and retard ignition timing. Use a steady gloved hand to slightly rotate the distributor in either direction until the timing is within the manufacturer's specifications.

Step 3: Tighten the adjusting nut. Once timing has been set at idle, tighten the adjusting nut on the distributor.

Have a friend blip the throttle. This involves quickly pushing on the accelerator pedal to increase engine RPM and then releasing it, allowing the engine to fall back to idle, therefore confirming the timing is set to specifications.

Congratulations! You have just set your own ignition timing. In some cases ignition timing will be out of spec due to a stretched timing chain or belt. If, after setting timing, the vehicle is showing symptoms of untimed, it is recommended you consult a certified mechanic, such as one from YourMechanic, for further diagnostics. These professional technicians can set your ignition timing for you, as well as make sure your spark plugs are up to date.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance Related Trouble Codes: P2158: Vehicle Speed Sensor B P2160: Vehicle Speed Sensor B Circuit Low P2161:...
P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed Related Trouble Codes: P2441: EVAP Vent Valve Stuck Open EVAP trouble...


Related questions

Q: Jeep taking too long to start

Hello. I believe your problem may be the crankshaft position sensor located on the side of the transmission near the engine. That is the most common cause of this engine not starting quickly. A technician from YourMechanic can come out...

Q: I got code P0016 and P0008. I just want to know what caused the problem and which one is bank 1 sensor A?

Hello, this problem (both codes apply to the same problem) relates to a calculated "bad timing correlation" between the crankshaft and the exhaust camshaft for cylinder 1 (cylinder head at front of the car). Engine management has tolerances for the...

Q: Truck not starting properly.

Hello, there are two different directions for a no start. The first being the starter doesn't work to start the engine. There are two thing to check here: that the base motor turns over manually, and that there is power...