LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Help - Weird upshifts

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Old Jan 17, 2004 | 03:43 PM
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davepl's Avatar
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Help - Weird upshifts

Yesterday was the first day with the new 396 LT4 and the 2800 stall Vigilante. Everthing was fine, transmission-wise.

Today, it won't upshift until 3-4000 rpm even under very light throttle. I've double-checked the ALDL data stream and it shows a full 0-100% sweep on the TPS (it only goes to 4.25 volts max, but even though I will improve that its enough for the PCM to want to shift).

The only other thing I can think of is I have a 2-bar MAP (I have a FAST ecm that's actually running the injectors and timing), but that's not new, and hasn't been an issue before. All the trans tables seem to be TPS related.

Any ideas?

Thanks,
Dave
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