Calling timing experts
Thread Starter
Pro
Joined: Dec 2002
Posts: 522
Likes: 3
From: Rolling Meadows IL
Calling timing experts
I am chasing some knock counts (again) and I forgot if the table included the base timing or not. So I figured I’d measure it. I had my scanner hooked up and I had 40 degrees at idle. I should have had 26. I unplugged the scanner and now I have 26 degrees. Does anyone know why the ECM added advance when the scanner was connected? 
If you have the scanner connected is timing advance added anywhere else.
If you have the scanner connected is timing advance added anywhere else.
Thread Starter
Pro
Joined: Dec 2002
Posts: 522
Likes: 3
From: Rolling Meadows IL
I measured it with an advance timing light. The kind that has a dial on it that you turn to get the strobe to show 0 degrees on the balancer, then you read the advance off the dial.
I was not scanning the car I just had the ALDL cable hooked up. When I removed the 10k resistor between port A and B the timing dropped to what was programmed in the chip.
I was not scanning the car I just had the ALDL cable hooked up. When I removed the 10k resistor between port A and B the timing dropped to what was programmed in the chip.
Pro
Joined: Sep 2001
Posts: 542
Likes: 1
From: Stuck in the 80's
Interesting. I would not think just hooking up a scanner would affect timing like that, unless it was in some sort of diag mode.
I know when I first begin to scan my RPM's will rise for a second or two, then settle back down to normal, like the timing has temporarilly jumped up, but never stayed that way.
What does the scanner read at idle? Should be total timing in the chip, the ECM does the addition (or subtraction if you will) of the base vs. total.
I know when I first begin to scan my RPM's will rise for a second or two, then settle back down to normal, like the timing has temporarilly jumped up, but never stayed that way.
What does the scanner read at idle? Should be total timing in the chip, the ECM does the addition (or subtraction if you will) of the base vs. total.
Drifting
Joined: Nov 2001
Posts: 1,783
Likes: 2
From: Latham NY
I can remove the 10k ohm resistor once Datamaster or TunerproRT connect with the ecm. Leaving the resistor in place will add some timing. Also, make sure you're in closed loop when looking at the timing numbers.
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