1997 Lexus LS 400 Repair Question
What is the difference between spark advance in degrees and ignition timing?
Spark advance is the computer advancing the timing or retarding of the timing.Verus the ignition timing which is the actual position of the distributor in the engine in relation of distrubutor to the rotor which you can advance the timing or retard the timing by turning the distrubutor.Setting the intail ignition timing you would set the number one cylinder on top dead center and have the rotor pointing at the number one post for the number one cylinder on the cap.when reinstalling the distrubutor just to give you a example of actual ignition timing.So at idle when warm it misses?
They are referring to the same thing. The spark has to occur before the piston gets to top dead center because the gas and air do not explode; they burn rapidly, and it takes some time for that to occur. The spark has to occur at varying times before top dead center depending on engine speed, load, temperature, and other factors.
Since the Engine Computer can't get a timing pulse from a sensor, then fire the spark plugs a measured amount of time BEFORE that pulse arrived, there is quite a bit of initial timing advance built in to that signal, then the computer varies how long of a delay is needed before the spark should occur. For example, the pulse might be designed to arrive at 30 degrees before top dead center. If the calculated desired spark timing is 10 degrees before TDC, the computer waits 20 degrees after the signal arrives to fire the ignition coil. The spark advance in this example is the desired 10 degrees before TDC.
But that is in refrence of the actual phsical intail timing of the distrubutor which i was talking about before.I belive thats what they were asking.
So the advanced spark I'm reading on my obd2 tool is the same is ignition timing?
1 question asked
That would be the actual timing and where the computer is adjusting it too.
I tried multiple ways to say it but no matter how it came out it is a real simple answer that gets way too complicated by trying to explain it. Your scanner is displaying the number of degrees before top dead center that the spark is occurring, ("where the computer is adjusting it too"). The ignition timing, or "timing of the spark" is the same thing, just different terminology.
Oops. Let me clarify; I don't mean I tried explaining to YOU multiple times and you didn't get it. I meant I typed a reply, proofread it, didn't like it, deleted it and started over, didn't like what I typed, started over again, and still found my reply to be confusing.
You might be over-thinking this too and are getting "wrapped around the axle" over a simple concept.