[Gmecm] Two '747 problems

[JD]

In the "good old days", this would sound like too much carb for the engine. Since the 454 Tbi is larger and the manifold most likely has larger passages, do you think that could be the problem. Essentially you have GM's largest TBI on it's smallest V8. When the throttle valve opens, that's alot of air for a 5 liter to swallow. This may not explain the idle as much as the stumble problem. If the butterflys are not closing completely, it might explain the idle, too. Have you removed the cover and set the base idle with the ESC bypass disconnected?
I'm new to the list and probably don't know what I'm talking about, but as an "old" GM tech, that's where I would start.
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