Why would car die after idling for short period and when I apply acceleration? on 1990 Nissan Maxima

1986 maxima- high mileage but ran great with no fluid leaks. Fuel pressure and fuel pump checked out. Replaced crank angle sensor (complete distributor). Replaced Throttle position switch and cleaned Mass air flow meter and sensor with cleaner specifically for MAF sensor. Checked voltage and ground at connector. The ECU has self-diagnosic mode which consistently shows two codes: load signal and Throttle position switch/circuit. My haynes manual offers no clue as to what comprises the "load signal".

Asked by for the 1990 Nissan Maxima
do you have eng codes if so post so we can adv

The Self-diagnostics codes are:code 23 and code 31. According to Haynes Repair Manual, code 23 relates to "Throttle Valve switch circuit" and Code 31 relates to "E.C.U.system". The E.C.U. unit itself contains a listing of the codes on the back panel. It shows code 23 relating to "idle switch circuit" and code 31 relating to "load signal".Of course, these are not ObD I codes. Thanks for your response to my inquiry.
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