5S-FE Ignition Timing Advance BTDC (OBD2)

[fenixus]

ehhh, started checking on my resurrected zombie ride again and something told me to check how the Ignition Timing Advance on cylinder #1 looks like.

... so in my obd2 scanner it's between 6-8 degrees BTDC at normal idle (gen4 norm specs say 5-10 is OK).

Then I remember someone had this check procedure that required to jumper DLC1 pins, IIRC they were Tc1-E1 (same as for reading all blinking codes I think)...

now I check timing advance again ... and it sits dead at 7 degrees BTDC ... errrr ... shouldn't it be set to 10 BTDC ?

how someone could adjust timing advance on gen4 while there is no distributor? assuming that timing advance is controlled by ECU solely, which sensors provide data for it? I'm pretty sure I ran through all of them in past already, but would like to make sure I'm not missing something obvious...

[71Corolla]

What you need to do is get some REALLY long ignition wires, which delay the timing enough to get you to 10 degrees.

Being serious, I don't see how you can change the timing, and bridging the terminals probably just prevents the ECU from changing the timing depending on engine speed. Just guessing here, but as long as you don't have any codes, everything is probably fine.

[fenixus]

wait a second ... so the automatic BTDC depends on current RPM speed? mine is a little in lower specs like usually around 700 but sometimes dips to 670, some other times rises to like 720... let's say it's close to manual 700+/-50 (for gen4).

.. what if I set it manually (by turning Throttle adjustment screw) to 750+/-50 ? the ignition advance would grow then together with it? ... not sure if I am getting it right.

but let me say this. this car was idling perfectly quiet and shake free when I bought it at 35k miles, you couldn't hear or feel the engine was running when sitting in car... well 45k miles later I definitely HEAR it and FEEL it no matter what I do LOL
it still drives good, if not even better then before ... but there is something weird about idle still despite all my efforts haha... another symptom is slightly lower than expected MPG, not much but still a few MPG are missing always.

was thinking, maybe if I (somehow) made the ignition timing advance to point at 10 BTDC it would get better again finally?

[Jason.MZW20]

The camshaft and crankshaft position sensors send output to the ECU for ignition timing.

For the 1MZ, Toyota lists 8-12*BTDC at idle in neutral with no accessories on with TE1 and E1 shorted. The 5SFE is 5-10* as you stated. So, the ECU is putting timing right in the middle of the range.

The ECU varies the timing advance to control the idle speed. So, if you adjust the throttle, the ECU will just override it. If you put the throttle outside the range of the IDL pin in the TPS, then the ECU won't know when the engine needs to idle.

[fenixus]

Originally Posted by Jason.MZW20

The camshaft and crankshaft position sensors send output to the ECU for ignition timing.

For the 1MZ, Toyota lists 8-12*BTDC at idle in neutral with no accessories on with TE1 and E1 shorted. The 5SFE is 5-10* as you stated. So, the ECU is putting timing right in the middle of the range.

The ECU varies the timing advance to control the idle speed. So, if you adjust the throttle, the ECU will just override it. If you put the throttle outside the range of the IDL pin in the TPS, then the ECU won't know when the engine needs to idle.

so 5-10deg BTDC is supposed to be with Te1-E1 shorted? mine is pretty much same shorted or not at idle (Park or Neutral with all accessories OFF).
I have adjusted Throttle screw in past 2 times, so hell knows what's it set to in relation to factory throttle setting LOL
the yellow paint marker on it is long gone.

... so in other words, leave it alone?

[Jason.MZW20]

Originally Posted by fenixus

... so in other words, leave it alone?

Yes!

For some reason or another, Toyota limits the timing advance on the 5SFE. It could probably produce a bit more power, but they chose to keep it down.