Very Hard Cold Weather Starts
 

Hello everyone. I have a 2001 Yukon XL with the 5.3 Vortec. I have a cold weather, 30 degrees and colder, hard start problem. It started a year or 2 ago, where the first start of the day, it will start, but idle horribly, stumbling all over itself like it's struggling for fuel. If you don't give it gas, it will die. After a few tries it will be able to hold an idle, though not a normal one, and warm up. It does not seem to do this on anything but the first start of the day. Only other thing is there is more exhaust smoke than normal, a whitish/greyish smoke. The truck starts fine at warmer temps. The fuel pump is not quite 2 years old, a Delphi unit. I have replaced the IAC valve. I have done a fuel pressure test to check for injectors leaking, seemed ok. It has only thrown a code once, I believe it was a real violent start shaking and everything. I don't exectly remember the code - it was last winter - but it was for the o2 sensors. I am just wondering if o2's could cause this or what it might be? Thanks in advance for your help.

What about the spark plugs, checked or replaced? Injecters may need cleaning. The smoke may be condensation in the exhaust system and is more noticable on cold days. Too much fuel and it would be dark. Light colored smoke is water related and you would know if you were loosing radiator fluid from your temp gauge. A weak spark would make it hard to start but I think you would see dark smoke out the tail pipe from un-burned gas. The O2 sensor before the cat. converter will cause the computer to adjust the injector fuel delivery to bring it back to the right ratio. The O2 sensor after the cat. is an advisor only on the condition of the burnt fuel but does not cause an adjustment.

I did spark plugs about 2 years ago, they're due to change. I wondered about the injectors. I try to run some Lucas through it when I remember to. I definitely don't have dark smoke. I guess I'll try some cleaner and plugs and see if that helps before I shell out $ for o2's. Thanks for the reply.

Check for a leaking fuel pressure regulator.

I'll add that to the list. I just don't know why it only starts crappy in cold weather. It even runs fine after it warms a little. It's like the cold is making something stick open or closed. I wonder if it's getting too much air? Would that cause that problem? I will just have to check some more things and dig deeper. Thanks for the help!