[Gmecm] Two '747 problems

[David Haggard]

I have two tuning problems I can't seem to figure out. The ECM is a
'747, '88 305, moderately cammed, 454 TBI and Holley Pro-jection intake.

1. After cold startup, the idle will never settle down to a smooth idle,
even after driving and fully warmed up. The idle oscillates between the
target setting and about 1800 rpm. The throttle follower seems
overactive. But once the engine is warmed up above the closed loop
threshold, if I shut the engine off, wait ten seconds, then restart it,
I get a smooth idle at the target setting, and the throttle follower
acts perfectly.

2. I have a bad flat spot under gentle acceleration, between 1600 and
1800 rpm. I experimented with lowering the PE TPS threshold to 20%, and
the flat spot is gone if I open the throttle past the 20% point and PE
is enabled. The flat spot is there under any acceleration below the PE
TPS level. The main fuel table has been tuned to give BLM's of about 126
in that RPM and throttle range, using WinALDL. The spark table has a
smooth, straight-line advance curve through that RPM range.

Any ideas would be greatly appreciated.

David Haggard
   '88 Formula Firebird "SR-71 Black 'Bird"