Engine Ignition and Cam Timing for the Novice

Key in the ignition
  Greg Ceo / Getty Images 

Ignition timing is tough to understand, but easy to adjust and set. Just for your edification, I'll go into the what's what on timing on this page, but if you have zero interest in all of the complexities of ignition timing, why it's important to how well your engine is running, and why it can be disastrous if it's off, you should skip all of the tech talk and simply get out your manual to make the adjustments.

What Is Ignition Timing?

Your engine is a complex symphony of rapidly moving parts -- pistons, rods, valves, pulleys, camshafts, a crankshaft -- all of these heavy, strong pieces are moving with great velocity inside your engine. Your piston moves up and down, the valves move in and out, the connecting rods push and pull, and the crankshaft spins wildly at the center of it all. This symphony plays itself out thousands of times every minute as you drive down the street.

There are two kinds of timing that take a seat at every engine event. The first is called cam timing, the second is ignition timing. Cam timing has more to do with all of the heavy stuff moving fast inside your engine. Remember the valves and pistons? Both of these are moving, and the piston is moving with the explosive oomph provided by the other cylinders in your engine. Your engine has a timing belt or chain that does a lot more than take energy from the spinning crankshaft and use it to spin the camshaft or camshafts. Its job is to make sure the valves are out of the way when that piston comes flying toward the engine's head. In some engines, the piston can actually impact a valve at the top of its movement. In these engines, called "interference" type engines, even a slight slip in cam timing can be catastrophic and result in a complete engine overhaul -- thousand of dollars. This is one reason it's so important to inspect your timing belt for wear or damage.

Luckily unless you've been doing some serious work on your car, the cam timing is probably right on the money. If it wasn't, you'd know it because your car would be running horribly, if at all. Your ignition timing, on the other hand, can be throw off by any number of little things. The good news is it's just as easy to adjust and reset. A little history: The engine in your car or truck has 4 cycles. Each one of these cycles is repeated in each cylinder. First, it sucks in air and fuel. Most new cars use direct injection so the air gets sucked in through the intake valve while the fuel is blasted in by a precise injector. The second part, or stroke, in each cylinder is called the "compression stroke." Now the air-fuel mixture is literally compressed tightly. This creates heat and volatility in the mixture. The third stroke is the ignition or combustion stroke (now we're getting somewhere). At this point the spark plug fires and ignites the air-fuel mixture, causing the piston to be pushed back down to the bottom of the stroke. The final stroke is the exhaust stroke. At this time the exhaust valve opens up and lets the old, burnt mixture out so we can suck new stuff in and do it all again!

The key to this whole operation is making sure the timing of that spark is on cue. A fraction off and you get an engine that is working against itself, which will cause a loss of power and choppy idle. A little more off and you can get some serious fireworks when you don't want them! No spark? Try testing your coil!

Timing Adjustment Basics

Now that you know what timing essentially is, I can tell you the basics on how to adjust and set it on your engine. Timing is different on every engine, so it's a good idea to have a good service manual handy to talk about the details in your engine. Newer engines adjust the timing themselves, so as long as your sensors are all functioning as they should, you won't have to do any tinkering with timing. In fact, you usually can't unless you remap your ignition computer's chip or buy an aftermarket performance chip that has a different timing map flashed into it. Be careful because the wrong chip can not only make your car run badly but can also throw error codes and bring on the dreaded Check Engine Light.

If you're cool enough to have an older school car or truck with a distributor that you can put your hands on, adjusting the timing is as simple as giving the distributor a twist. You'll need a timing light. With the light wired up per the instructions and the engine running, point the light at the main pulley that comes off the crankshaft. This pulley has a notch or mark on it. On an engine timed to zero degrees advance, also known as Top Dead Center, that mark will appear to flash with the light pointed at it. If you loosen the distributor and turn it slightly, you'll see that mark move to the left or right. Turn the distributor too much and the mark will leave entirely. You can also shut off the engine in this way. On most crank pulleys, there is another mark. This is the mark you aim for, usually somewhere between 3-5 degrees before Top Dead Center. All you do is turn the distributor until that timing mark is flashing at the right spot every time. Once it's set, tighten the distributor so it won't turn on its own, and you're good!