no advance ls2
10-24-2012, 06:56 PM
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no advance ls2 i have a mid engine corvair with ls2 mated to corvette c5 transmission and diff. i have no spark advance. i`ve changed cam and crank sensors and double checked all my wiring. all is good. when i run it with scanner on live data, i have 0 spark advance. the cam and crank rpms are only about 150 rpms differance when i rev the engine to 1550 or 1750, the cam and crank rpms are 10 or 20 rpms differance. i thought the crank and cam should be 2 to 1 nomatter what rhe rpms are. anybody no what the heck is going on here?
10-25-2012, 05:08 AM
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I an no expert on the subject but I think of the top of my head the rpm should match. Actual rpm is componsated. Anyway that needs more research. Meanwhile good to know year of things like pcm, motor. Any change to motor? Cam sprocket? Crank reluctor? What color sensors and were?
10-25-2012, 11:38 AM
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A 24x is correct for 06. On with your problem, Myself and another gm tech were discussing this and questioning your actual concern. We are use to reading crank as engine rpm and cam as say 2x yes or no.
10-25-2012, 06:57 PM
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correct, i thought cam would be twice the rpms as crank is. mine isn`t like that . with genysis otc scanner on live data if crank is at around 750 or 800, cam is only about 150 rpms higher. when i rev engine to 1500 or 1700, cam is 10 or 20 more than cam. that just doesn`t seem right
10-25-2012, 08:44 PM
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The "crank rpm" and "cam rpm" are both the engine speed, they're just calculated from different sources by the PCM.
Are you sure you're looking at the correct spark advance parameter...?
Have you marked the crank pulley and used a timing light to see what is really happening...?
If timing really is zero then you have to somehow find out why the PCM is doing this (this is where you need the right software)... is traction control always kicking in causing the PCM to remove timing...?
Are any DTC's present...?
Are you sure you're looking at the correct spark advance parameter...?
Have you marked the crank pulley and used a timing light to see what is really happening...?
If timing really is zero then you have to somehow find out why the PCM is doing this (this is where you need the right software)... is traction control always kicking in causing the PCM to remove timing...?
Are any DTC's present...?
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10-26-2012, 08:40 AM
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This u motor for 06 should not have any cam phase ability. I think you may be looking at cam crank offset. All the same it should stay in the area of 2 degrees. Also look through your scanner for special functions and perform a crankshaft variation/ offset relearn. And like joecar said check ignition advance the old fashion way. Let us know.
