I am a little confused with the whole GM Electronic Spark Timing thing.
I own a 1989 Olds Cutlass Supreme with the 2.8L engine. This engine has a compression ration of 8.9:1
I have been using a Scanner lately to check my timing, and I'm somewhat confused. Mostly because there's really no definitive information online as to what is considered NORMAL timing for these EST engines.
Tonight I did a Data Capture while accelerating hard into 2nd gear. At idle, my Spark Advance was at about 18-19 degrees. At 4200 RPMs it's at about 27 degrees. The highest it went up to was 33 degrees, but it hit 33 when I let OFF the throttle from about 50 - 15 percent? This again, makes no sense to me. Why would the Spark Advance increase when I'm slowing down, off the gas?
Another thing, my Knock Sensor always detects 1 or 2 knocks when I accelerate fast. It usually detects knock only above 4000 RPMs. But, for some reason the Spark Advance doesn't Retard any degrees? In fact, tonight Advanced MORE?
I highly doubt there's anything wrong here, but I'm just making sure my Electronic Spark system is OK.
So, are the above Spark Advance figures "normal"? Is there really any "normal" amount of Spark Advance?
Is there any test I can do with this Scanner, while I have it, to check my timing?
Does anyone have any good links to websites that talk about GM's EST?
THANKS!:)
PS I run 91 Octane Shell gasoline, if that matters?