Ongoing problem with car sputtering and dying in traffic or while sitting idle
 

Hello first post here but have been following for a few months now.
So I've had problems with my 09 SS since I bought it. It does not like to stay running after it's in traffic for a while or sitting idle for a few minutes. The rpms bounce and it eventually dies and is hard to restart. I have had a tech 2 computer hooked to it while it does this and the technician still could not figure it out. Up until a few days ago i have not thrown any codes so it has been tough to know where to look. A few days ago while driving it threw these 3 codes. If anyone has any suggestions to what my problem is please chime in. I have replaced plugs, coil packs and upstream 02 sensor. The codes are now gone but the problem of it dying is still there. Engine was replaced at 76k and rod bearing replaced around 98k all under warranty by the dealership and it now has 102k on it. Valves were scoped and looked good so them being dirty is not the culprit. I am leaning toward the engine harness, underhood fusebox or the ecm but I have spent a ton on it already and really need some help to what it might be. Any help will be highly appreciated because I love this car and really want to drive it more.
https://cimg0.ibsrv.net/gimg/www.che...04635f2da9.jpg

Welcome to the site,
The codes, what were they?
Why throw those parts at it?
fuel pressure both high and low?
loose fuse box halves and ground wires aren’t hard to check .
how is the battery?
Whats the voltage?

How about a compression test? Very easy, might be revealing. Auto parts stores have the tester as "loaners".

P0300, p0301 and p0302 were the codes. Battery is new and the alternator tested good. I have had this car at the GM dealership 2 times and they had no clue what it could be because it wasnt throwing codes. The Chevy tech that decided to help me on his own spent hours at his house trying to figure it out and all he could figure out with the tech 2 is something is throwing the timing off randomly when it gets hot but again no codes are being thrown when it does it. I have a couple videos that I am going to load showing exactly what it does.

I have messed with the fuse box wires and could not get it to act up. It also has the gms1 kit and the new map sensors are only crimped not soldered so that might be it.
The pressures were good according to the tech.
I will look into the compression test but the tech also said he was sure my problem wasnt there after watching it on the computer for hours.

A wild ass guess, but what about your throttle body cleanliness? Your IAC sensor may not be throwing a code, but if your throttle is sticking under idle conditions, it could be not doing what it's supposed to be. Spray it clean with a cleaner (CRC is my fave), and see if it helps.

If the throttle body is the issue, it will be all gummed up . You can see it with a mirror even before cleaning. I hope this helps.

Prevention goes to the catch-can thread...

"the new map sensors are only crimped not soldered" - get them soldered asap to rule them out.

The throttle body was cleaned by the GMC dealership.
It seems to happen when it gets hot. For instance when it was cold out it only did it after sitting in traffic for a while or just sitting idle but now that its warm it will happen at stop lights.
So what type of shop should I take it to for the soldering of the sensors? The dealership acted like they dont do that when I asked them about it.

The reason I was thinking engine wiring is because the problem started happening after the new engine was put in and slowly got worse. So maybe they might have nicked it or something. Plus no codes are being thrown really so seems like it would be something outside of a sensor or fuel/air delivery causing it.
I really appreciate the feedback because I want to get this sorted out so bad and the people around here that should know something dont have a clue.

I believe we have a bingo !

Why are you going to a dealer for this work? Are they giving you some kind of break? I doubt there is a mechanic that has been around for 8 years. Why would they know anything about an extinct car?
Any body could solder it for you, just be prepared for a lot of hours. I don't think it would take more than an hour, but it is such a pain they probably will charge for more. I guess you could try to find the newer model plug and play harness at a junkyard or ebay.

THIS is why we exist here... Insight born from experience, or reading it for 10 years... LOL This is clue #1.