Iac data erratic when hot
 

97 Sentra. Manual trans. IAC data is all over the place when hot. Car will buck & jerk bad, have to let sit for hours or overnight for problem to stop. Usually takes half an hour of driving for problem to start. Prior to that runs great.
Already replaced valve twice. Replaced distributor & MAF for grins, have inventory of used parts. Cat is not plugged. Found Signal wire from crank sensor broken, repaired that. Replaced fuel pump, checked filter. Timing chain & components have been changed. All data stream looks good other than IAC when problem occurs. No codes, thinking pcm issue? what does somebody have to say to enlighten me? Thank you!