1228746 TBI 305V8 stumble

[Shannen Durphey]

Jay Vessels wrote:
> 
> BCC is APFN,
Here's what GM says about that BCC:

 Some owners may comment of a cold engine knocking noise. This  noise  may  be
 misdiagnosed as piston slap resulting in unnecessary engine replacement.

 The noise may be caused by detonation at ambient temperatures  less  than  40
 degrees  F  (4  degrees  C).  Refined  spark  control  tables  in  a new PROM
 specifically address this detonation condition.

Hmm...  Wonder why the car you raided was in the junkyard. ; )
New calibration is ATYR, FYI.

> Timing goes to about 12 degrees (from a
> > base of 0) with bypass plugged in so I believe the advance circuitry is
> > right.

Ya know, I thought there was something wrong with your timing setting.  GM says
base timing should be 6 degrees for that year engne. Don't bother with any
further diagnosis until this condition is corrected. : )

FYI, most 8cyl TBI pickups use a base setting of 0 degrees, while most cars use
a setting of 6 degrees.
Shannen
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org