I have a 2007 Classic Silverado 1500 5.3. It's basically been thrown together with leftover 2006 parts and a smattering of 2007 bits. Hellish to lookup parts for. Anyway, lately it's been having a really rough time starting up for the first time regardless of temperature. It hasn't not started, but when it does, the idle is super rough and if I don't goose the throttle, it will die. After about 10-15 seconds, it's fine and seems to run fine. Trips to town, off then start again it has no problems. The engine light came on and it shows codes P0172 and P0175 which seem to indicate the engine is running rich. I'm trying to nail down the root cause, but don't have a lot of $$$ to throw away on it.

Basically, I'm looking to see if anyone has an input on the MOST likely scenario and how to detect it. I've replaced the air filter already and ran some Seafoam through it (for good or ill) but the situation has continued to get worse. I'm concerned that one of these days shortly it won't start at all. Any help would be appreciated.

 

I'm thinking maybe your MAF sensor needs a good cleaning. When I first got my truck, it wasn't a super rough start, but it wasn't smooth like it is now. One of the first things I did was clean that sensor (with MAF cleaner). It actually made a fairly dramatic difference in the idle. I want to say that a dirty MAF could be giving bad info about how much air is actually getting in, so it's enriching the fuel to compensate. I could be mistaken though. But one of the easiest things to try that has basically no downside.