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AE86 16V - How to set ignition timing...

Posted: Tue Apr 29, 2014 1:02 am
by jondee86
One of the most frequently asked questions asked on the AE86
forums is... "How do I set the ignition timing ?". And rightly so,
because correct ignition timing is one of the fundamentals of
tuning any engine. It is also an incredibly simple procedure once
you understand the basics of ignition timing. So here we go....

THE TOOLS YOU NEED
1. A timing light. It does not need to be anything fancy. Just a
basic non-adjustable timing light from any store will do, so long
as it is the type that has a clamp to put on the #1 spark lead.
2. A 12mm (?) ring spanner for loosening the distributor.

THE PROCEDURE
1. Start the engine and allow it to reach operating temperature.
2. Check that the engine is idling at 850-900 rpm.
3. Attach your timing light to the battery and put the clamp on the #1
spark plug lead. Check that the lamp flashes when you pull the trigger.
4. Put the engine in "diagnostic mode".
5. Point the timing light at the timing notch on the crank pulley.
6. Observe where the notch sits against the timing belt cover scale.
7. If the notch does not hover at 10 deg BTDC, loosen the distributor
and turn it until the notch sits at 10 deg.
8. Tighten the distributor.
9. Take the engine out of diagnostic mode and check that the notch
now hovers around 16-17 deg BTDC.

Congratulations... your ignition is now correctly timed :)

Cheers... jondee86

Re: AE86 16V - How to set ignition timing...

Posted: Tue Apr 29, 2014 1:25 pm
by saiGone
Thanks for the write up!

Re: AE86 16V - How to set ignition timing...

Posted: Sun Jan 28, 2018 1:20 am
by aaronlee133
Hi Jondee, randomly came across this and made me wonder... I know to put car in diagnostic mode when setting ignition timing and to set to 10 degrees TDC BUT what does diagnostic mode do specifically in terms of setting ignition timing? If we know it should be roughly 16-17 degrees not in diagnostic mode how come Toyota doesn’t simply state to adjust timing to 16-17 in normal operation mode rather than having to first place in diagnostic mode and then set? Thanks -Aaron

Re: AE86 16V - How to set ignition timing...

Posted: Sun Jan 28, 2018 3:21 am
by totta crolla
The timing is locked so there is no fluctuation thus making setting it easier and more accurate.
There may also be a 'failsafe' in as much as any error codes would show before the timing is set.

Re: AE86 16V - How to set ignition timing...

Posted: Sun Jan 28, 2018 2:42 pm
by jondee86
As said above, the ECU locks timing so that the spark occurs at 10deg before
TDC according to the reading it gets from the crank angle sensor located inside
the distributor. Then the distributor has to be calibrated to the crank so that
the spark actually occurs when the crank is at 10deg before TDC.

If the distributor has been moved around the crank angle sensor inside has also
been moved, and the spark will now be advanced or retarded. Generally speaking,
this will be a bad thing if you expect the stock ECU to run a stock engine as well
as it did when it left the factory. So when you give a stock engine a tuneup, you
should always check that the timing is set to 10deg BTDC in diagnostic mode.

While it is possible to quickly set timing to 16-17deg without putting the engine
in diagnostic mode, it is not as accurate. Timing correction factors applied by
the ECU will be active. For example, temperature and engine speed. Locking the
timing at 10deg eliminates these potential sources for error, and provides a solid
base for calibration.

Aftermarket ECU's on modified engines also lock timing to allow ignition timing
to be calibrated to the crank, This applies regardless of the ignition system used.

Cheers... jondee86

Re: AE86 16V - How to set ignition timing...

Posted: Sat Feb 10, 2018 12:53 am
by matt dunn
The idle contact in the TPS must also be closed to achieve correct timing,
although the CEL will probably flash a switch code if it is not set correctly.

Re: AE86 16V - How to set ignition timing...

Posted: Thu Feb 22, 2018 8:41 am
by Jinsoku
never saw this post.
good info jondee86!!