e40 timing off by 20 degrees(lower) than comanded help

[saleen9973]

I just finished up my turbo build on my 2005 gto its speed density, i had a centrifugal blower on it last year. My problem is my idle timing, i have it set at 24 degrees but idle advance is 4 degrees. so i started playing with the timing to see what happens and no matter what i set it to it is always 20 degrees lower ie i set it to 45 and it was roughly 25 i set it to 37 and it idles at 17. Set at 24 with only 4 degrees is bad because the fuel is igniting late in the headers and causing them to glow. if i set it to 45 degrees its great except the damn idle is at 2k because of the overly aggressive idle timing. can some one lead me in a right direction my head hurts from spending the whole day making changes.

[kevin87turbot]

You've got a vacuum leak. That will cause all of the symptoms that you are having. It's retarding the timing in an attempt to reduce the idle speed to your target.

[saleen9973]

i was thinking that, i sprayed brake cleaner around but didnt hear any change in the rpm. i will dig further in and try to get my hands on a smoke machine or make my own. thanks for the reply.

[saleen9973]

i may pressurize the intake with 3psi through compressed air and spray soapy water around and see if that works

[blindsquirrel]

25* (or even 45*) will not cause a 2K RPM idle speed... unless there's too much air from somewhere.

Why does the throttle position never, ever go below 18.82% no matter what? Is it sticking? Can you push the blade closed (key off)? Does it cycle the blade from the at-rest position to closed back to at-rest like it should at key on?

[saleen9973]

I do hear it click and do something key on. I will take the throttle body off tomorrow and take a look at it.

[saleen9973]

Today I removed the intake and re did some vacuum lines. After putting it back together things seem better. Timing is no longer 4 degrees but it is fluctuating between 18-24 and the idle is still a bit high at 900 vs the commanded 825 but that is probably the ve or the base running airflow. I called it quits after I got it fired and lings looked better. Tomorrow is another day I will keep you guys posted.