Improper Ignition Timing

timing tester
Timing Tester

Improper ignition timing can cause several car problems. Anything from hard starting to lack of power might be traced back to the root cause of incorrect base ignition timing.

In rare occasions I have also seen a hard start condition from this as well. Often when people are having poor performance from their engine they may wonder if it is an issue with the engine timing.

You have to remember that poor engine performance can also be caused by poor compression, overheating, incorrect valve timing that can be caused by a timing belt that slipped one notch. Clogged catalytic converters and probably about 20 other things can also cause this condition.

How to test for improper ignition timing

When the ignition timing is not correct there are a few tests that can point to the car problem. The main symptom of a timing issue would be incomplete combustion at different engine speeds. Incomplete combustion can cause an excess of oxygen in the exhaust stream.

In this case the powertrain control module will try to compensate for this imbalance of the air fuel mixture by changing the injector on time to straighten out the mixture. If you have a scan tool that can read the data stream you can pull up the fuel trim mode and see if the computer is forcing the injectors to stay on longer or shorter.

If you have exhaust gas analyzer such as the kind that is used by automotive shops and inspection stations you can sample the exhaust stream and read the amount of oxygen. You can also pull up the oxygen sensor data stream on your scan tool and see if the voltage is changing properly.

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Vacuum test for incorrect timing

The vacuum gauge is inexpensive and handy device that can quickly perform a few tests that can help diagnose lack of power problems from clogged exhaust among others. Incorrect ignition and valve timing also affects manifold vacuum readings. If you connect your vacuum gauge to a strong manifold vacuum source and low readings are observed you can adjust the base timing to see if the readings are able to be brought back into specifications.

Another telltale sign of a timing problem would be excessive engine ping. Engine ping is referred to as cylinder pre-ignition. This is when the air fuel charge is ignited at the wrong time. If it is ignited before top dead center it can cause the valve train to generate a noise that is known as engine ping.

In most cases engine ping is caused by timing that is too far advanced. If the timing is too far retarded the most likely symptom would be a hesitation lack of power and very poor fuel economy. I am working on an article about using a timing light to check for improper ignition timing. It should be ready for my next weeks post here on the auto repair blog.