Hey guys this is Larry here. I have this 97 3.0. Bout got everything working on it. lots of new parts pretty happy with how everything is turning out got tranny & paint after Xmas but I’m still looking for a way to slow the idle from 900 to maybe 700 or 750. Looking @ a Diablo tuner.at $300+ Maybe a little xtra power +economy be nice. Anybody got any input? Chime in...
Larry

 

After engine is fully warmed up and idling
Unplug the IAC Valve, it will close all the way
RPMs should drop to about 500, barely running, or engine may even stall, either is GOOD, it means no vacuum leaks

If RPMs do not drop then there is a vacuum leak or,.................................someone has messed with anti-diesel screw on throttle linkage, a big no-no
Look on throttle linkage for a screw
Turn it counter clockwise(unscrew) and see if RPMs start to drop, if so keep turning, someone F*ed up, until engine is barely running, and its set again
If RPMs do not drop then turn it back to where it was
You have a vacuum leak, causing the higher idle

A 3.0l with automatic will idle at 800 in gear, maybe 750 in Park with AC OFF
From early 1990's Idle RPMs are more about emissions than anything else
And idling engine is a big polluter, so higher RPMs are better, less bad emissions, so computer may indeed need to be reprogrammed to lower the warm idle RPMs
Now-a-days engine have to be shut off when you stop to meet new idle emission levels, no this was not done to save gasoline, lol, its done to pass idle emissions tests

Have no experience with Tuners
But the only way to get better performance and MPG both is to install an electric fan on radiator, mechanical fan lowers both