1979 Gen 3 Hemi Dodge cube van won't run above 3000 rpm for more than 2 minutes

Hi,

Just the facts.

1979 Dodge cube van

2007 Canadian spec AWD Chrysler Aspen 5.7L donor engine

A518 automatic

2003 Hemi 5.7L bellcrank setup for throttle input to PCM

Hotwire custom harness

PCM set up as 2005 5.7L with manual transmission

Completely stock type tune- runs EGR and front O2 sensors

Will run all day at WOT in overdrive around 2500 rpm. Hit a long hill with a head wind, drop it down into 3rd gear, and it will run perfectly for about 2 minutes. Then pedal input stops affecting throttle position. Engine goes to idle. Pedal position makes no difference. Slip transmission into neutral. Turn key to off. Back to ignition on. Hit starter. And it works fine again. For about 2 minutes. Temperature and oil pressure normal.

The only code it has set is P0501 which is all about a speed sensor input missing or out of range. This setup has no speed sensor and neither do a million other Hemi swaps.

I had Hotwire turn off code P0501 and nothing changed. They've never seen anything like it. None of the swaps they've been involved with have needed a speed sensor when they use an older style automatic or manual transmission.

It may be that this is the only swap that runs above 3000 rpm for so long. Nobody in a street or race situation would come across this problem. The throttle is not wide open for anywhere near 2 minutes. I just drove it on a 5000 mile trip across the continent and other than this glitch is was a blast to drive.

Ideas or suggestions are welcome. I have a few, but feel the answer is here with someone.

Thank you.

G.