1999 7.4 Vortec, Crazy issue has me stumped.

[Auto Recyclers WY]

We have a 1999 7.4 Vortec with black computer. Th400 trans, long tube headers, Bosch 0280155884 injectors. In a 1982 c10.
With all the sensors plugged in, the truck will not rev and goes lean and it is acting like the fuel is going off and on. It is not storing any codes. When we unplug the tps it will rev and the tables look a lot better, it may be a bit rich but it is definitely better than when the tps is plugged in. The tps is good. We have checked it and changed it anyway. The best I can figure is that when the tps is disconnected the tune goes back to the default table and whatever table that is pulling fuel is not active without the tps. I need help finding the problem.
Thanks, John

[abc]

I'm gonna go out on a limb and say that's a wiring issue. Find out what voltage the TPS is reporting with a closed throttle, then at WOT.

[Auto Recyclers WY]

I will check the voltage as soon as I get to the shop this morning. We did make sure the tps was reporting the right values. When the throttle is closed the tps shows 0%, when full open shows 100% and checked a sweep from 0% to 100% the values that the ecm shows from the tps are right as far as I have found from the tests yesterday. It does have a Howell harness and I haven't seen any evidence of issues so far with the harness.

[Alvin]

Have you verified fuel pressure ?

Log injector duty cycle also so we can see if it is actually a fuel cut.

[Auto Recyclers WY]

Fuel pressure is 60 psi, it will dip to 58 psi for a quick second when reving the engine with the tps disconnected. When the tps is connected and trying to rev the fuel pressure is steady at 60 psi

[Alvin]

What is it when your under load or when this problem shows up.

[gtstorey]

So that is fuel pressure while parked, not driving?

[Auto Recyclers WY]

So that is fuel pressure while parked, not driving?

Yes, that is fuel pressure when parked. We have not driven the truck at all. When the tps is plugged in, the engine will not rev. It just goes from 1200 rpm to 1600 rpm repeatedly. The o2 sensors go instantly lean when the tps is plugged in and we try to rev the engine. Also it goes open loop closed loop repeatedly while trying to rev.
I will log the injector duty cycle and upload it as soon as I can.

[Auto Recyclers WY]

The one log is with the TPS plugged in and injector duty cycles and all the other channels that I thought may help.
The other log is with the TPS unplugged to start and then plugged the TPS in at around 9:45,
The injector duty cycle goes to 0 when the TPS is plugged in and the throttle is opened and kind of jumps around for a second every once in a while. When the TPS is unplugged the injector duty cycle seems good.

[abc]

Have you inspected the TPS harness thoroughly? Inspect the connector for a stray strand of wire? Striped the loom off, inspect close with your eyes and a DVOM. If no problem found, make a temp. TPS harness and run it all the way to the PCM for a test. If no problem found, I would try another PCM.
On second thought, have you inspected all the grounds and back probed the TPS harness for actual voltage at closed throttle compared to WOT. I would check it at the PCM also.
I don't know a lot, but there is nothing I can think of in the tune side that could cause such an issue, I believe this has to be a hardware issue and/or a EMI issue.
The TPS circuit is either enabling the corruption of the PCM or it is the cause of it.

[Fast4.7]

I am going to go out on a limb and say that it could be related to the missing 4L80E inputs. The PCM may be interpreting it as a failing transmission and going into transmission abuse mode. Ran into this with a 350 manual swap and had to start with a 350/Manual PCM tune. Some of the L29 7.4L Vortecs came with the non-electronic 4spd Allison AT545 behind them although most were L21s in that application. I know the L29/non-computerized automatic file exist but probably be a nightmare to track one down.

[abc]

Fast and OP, do you think changing the abuse tables would help? I know it's marked as disabled, but the issue is happening near where the trans abuse settings are set.