Bagitupbaby

i got a 91 LX 5.0, and im having idling problems, it idles fine for 10 min then after that it starts dropping rpms to 600 then it starts to ping and knock when u pull up to a stop, i cleaned out the EGR, IAC and Mass air wires, reset the computer, then i replaced the tps sensor my mechanic put it in, i dont get a check engine light but after 20 min idling it throws it on, i checked the timing its fine, what else should i do?

Ninety5five0

The only thing that came to mind is the IAC, but you saiid you cleaned that, maybe try to replace it....