[Gregski]

Idle Tuning - Intake Manifold Absolute Pressure

Alright so now armed with all this information how do we tune our idle if indeed something is out of whack?

First of all on a stock engine we do not mess with the RPM setting, that has been determined by the GM engineers so our goal is to adjust the Timing and the Airflow to help maintain that RPM not to go around increasing or decreasing it. We leave that headache to the cammers ie the guys who installed a bigger cam, ha ha.

Again keep in mind this is with a stock engine, and when I say that, I mean stock drivetrain, so if any of you wise guys are like well my 5.3L is stock but I married it to a TH350, or strapped on some long tube headers with the O2 sensors a mile away from the engine... um no... that is not stock, ha ha.

So essentially the RPM ie the first part of the Holy Trinity is done, we just find out what we need to idle at based on the Base Setpoint table and we accept it.

This leaves us with Timing and Airflow. Let's start off by trying to dial in our timing. So lets assume we are just like 2 pounds off on our airflow, (so essentially we are good, or good enough, we don't see anything way off) so what I would do here is adjust the timing by increasing it until I found the highest vacuum or as the cool kids say these days lowest Intake Manifold Absolute Pressure.

So let's give that a go. First we need to add yet another channel, again this one goes up in the Attic, and it is called Intake Manifold Absolute Pressure read in kPa you are looking for the lowest number (low 30s would be awesome).