I'm posting this for a friend in hopes we can get his 87' Runner fixed with the forum's help. (It's currently in the shop, mechanic is stumped) I even took my 87'specific Toyota FSM to the mechanic in order to troubleshoot, but still no luck.

Symptoms: The truck started to have sporadic idle issues, also would not bump up the idle when the a/c was kicked on. My buddy went to go check the timing and noticed that the engine did not drop in RPM when the jumpers were put in place. In fact, no change at all with the jumpers in place. I don't know jack about EFI, but I had a hunch from reading here on the forum that it could be the TPS. When the motor is set at 5*, it stumbles bad and usually stalls. When experimenting with the timing, it will idle when the timing is set higher (above 12*). The machanic could play with the idle adjustment and timing, get it running great. When the truck was turned off and started again, the idle/stumbling issues would be right back again. Any help is greatly appreciated, thanks!

Classic "TPS Out Of Adjustment" symptoms:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Why do I think that? Because without the timing jumper installed the base timing is, you guessed it, 12 degrees BTDC. So if the TPS IDLe adjustment is out of whack, then the timing jumper does nothing, so you end up with 12 BTDC timing.

Thanks Roger, I'm printing off your info and taking it by the to my friend this afternoon. I appreciate the help.