Today we are looking at how to check and adjust the ignition timing on an engine equipped with efi (naturally this does not include distributor-less (coil pack) type ignitions). Engines that are controlled by an ecu require the computer to be put in a ‘diagnostic’ or similar mode before the ignition timing can be checked and adjusted.
The procedure for doing this varies widely between the different makes and models so you will need to find the correct information for your vehicle before attempting this. Workshop manual’s are a good source for this.
The vehicle we are using for this article is a ’93 Toyota Camry fitted with a 5S-FE engine (4cyl 2.2L). We start by checking that the timing marks on the harmonic balancer and the lower timing belt cover are easy to see. It is a good idea to mark the balancer and the correct timing position on the cover with a white pen or correction fluid (Liquid Paper) so that they can be more easily seen.
On the Camry we need to bridge the TE1 and E1 terminal of the diagnostic connector. The diagnostic connector can be found on the left hand side (passengers side) strut tower.
Open the lid and you will see quite a few electrical terminals. Inside the lid should be a diagram of the terminal layout and from that we can work out which two terminals we need to bridge across. The two terminals can be bridged with basically anything that will conduct, here we are using a split pin.
Now we can connect the timing light, start the engine and aim the timing light at the timing marks. In this case the timing is to be set at 10 degrees BTDC (before top dead centre).
If the timing is not correct, stop the engine and take a look at how the distributor is held in position (to adjust the timing the distributor needs to be rotated). In our case there are two 12mm bolts that have to be loosened. The bolts or nuts that secure the distributor only have to be loosened, not removed. If the distributor has not been moved in a while it may be difficult to get it to move at all. A GENTLE tap with a rubber or soft-faced hammer on the lower body part of the distributor (the area closest to the engine block) should get it moving.
The lower bolt is a pain to get to without removing the air intake!
Once the bolts are loosened restart the engine and rotate the distributor while watching the timing marks with the timing light. If the marks are getting further apart, the distributor needs to be moved in the opposite direction (yeah, pretty obvious I know!).
Once you have the timing set to specifications, re-tighten the bolts holding the distributor and run the timing light over the timing marks one more time. The reason for doing this is that the distributor often moves when tightening the bolts.
If all is good shut the engine down, remove the bridging wire and timing light and take the car for a road test. All done!