Cold start

[Bob Oke]

I have a 2020 Silverado High Country with the 6.2. My morning starts don’t high rev/idle anymore. It has a cold air intake and a flowmaster cat back. It use to sound great on cold start but not it sounds like it has been running right along on first start. 

[CamGTP]

Possible that the coolant temp sensor is reading the wrong values. If you had a scanner that did live data you could compare the ambient temp the coolant temp on a cold start before you fired the truck up.

 

If the coolant temp for example was showing 120+ degrees while the rear temp was 45 degrees outside, it will not go into a high idle/cat warm up idle. The main reason the exhaust note is more throaty is because of the cat warm idle, atleast that is what I call it. Cold starts will reduce ignition timing and in fact cause the timing to be negative or after top dead center, this causes the explosion to happen inside the exhaust manifold  instead of the cylinder itself. Doing this creates more noise but also heats up the cats way way faster to meet emission standards.

[Niklasbraun]

On 1/29/2024 at 12:35 AM, Bob Oke said:

I have a 2020 Silverado High Country with the 6.2. My morning starts don’t high rev/idle anymore. It has a cold air intake and a flowmaster cat back. It use to sound great on cold start but not it sounds like it has been running right along on first start. 

So, with your current setup, a couple of things might be going on. First off, the ECU could use a recalibration to handle the extra airflow from those cool mods you added. Check if there are any performance tunes specifically made for your setup.

And, about that change in engine sound you're hearing, it's a good idea to inspect for possible exhaust leaks or loose connections in the modified parts. Take a close look at the whole intake and exhaust system to spot anything off.

Oh, and if your Silverado has OBD-II, grabbing diagnostic trouble codes (DTCs) might clue you in on any problems the car's computer has picked up.

Edited January 30, 2024 by Niklasbraun