Need some direction....

[BIG*RED]

I have been having an issue with my 1993 suburban. It has the 5.7 tbi backed by the 4l60e. Anyways i have had this issue for sometime now, it never really bothered me, but now its starting to annoy me and I want to figure out what is causing it and how to fix it.

When i start my Burb when its cold (the engine not the temp outside) the volt guage sits at 14 volts, and the rpms according to the tac are right where they should be. But everytime the burb reaches operating temp the volt guage drops to 12 to 12.5 while driving. Then when I come to a stop at a light or stop sign the volt guage drops to 11-12 volts and the rpms drop down to around 400 rpm. And if I am running the A/C or the defroster and come to a stop I can hear the blower motor slow way down.

then when i start to drive again everything goes back up to where it should be.

I have installed a new alt, and even had it checked a couple times just to be sure its working right (plus it did this before I installed the new alt), new plugs, plug wires, cap, rotor, O2 sensor, intake manifold gasket, coolant temp switch, fuel filter. And I have checked for vacuum leaks.

anyone point me in the right direction please?

 

[zombie1969]

Remove the IAC and check the passages for blockages.Never turn the key on with the valve removed.Bumping the timing up a bit might help too.I forget what the spec on the TPS is supposed to be at idle but you can adjust the hard stop on the throttle body as long as you don't go over or adjust the TPS when done.