Runs terrible when cold.

[the blur]

1st cold start in the morning, 5.3L runs terrible for about 15-30 seconds. Stinks like hell from the exhaust. Runs very rough. Idles all over. Then after that, it's perfect.

Dealer replaced the MAF, but it didn't help.
2013 burb, all stock.

The dealer wants to reprogram the ECM. But I haven't went back yet. I think that's ridiculous.

Any other clues?

 

[07 black beauty]

Has fuel pressure been checked? Do you have a "check engine light" ? If so pull the codes and go from there. Just went through a similar issue with my Tahoe. I ended up replacing fuel pump module in gas tank.

 

[swathdiver]

Quality of your fuel, vacuum leaks, loose motor, condition of plugs and wires could also be in play. If it runs just fine afterwards, use the remote start feature and don't bother with climbing aboard until its up to temp and your interior is nice and toasty for the journey ahead.

 

[the blur]

The dealer just reset the fuel trims. Now it seems ok. It was so bad, it wouldn't start. 2 trips to the dealer....

 

[SLE2013]

Sounds like what I was going through... added a fuel injector cleaner on a full tank of gas, and used a tier 1 gas station when I filled up... issue went away. I spent $400 from the dealer with MAF replacement, computer update, AIS service and all it took was a $10 bottle of fuel injector cleaner and issue solved.

 

[Doubeleive]

Sounds like what I was going through... added a fuel injector cleaner on a full tank of gas, and used a tier 1 gas station when I filled up... issue went away. I spent $400 from the dealer with MAF replacement, computer update, AIS service and all it took was a $10 bottle of fuel injector cleaner and issue solved.

thanks for the reminder I have like 4 cases of that stuff sitting in the garage and I just filled her up at Costco!