Very Hard Cold Weather Starts

[wyelkhunter]

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.

 

[delta579]

Did you do a vacuum test yet ? Did clean the IAC seat in the throttle body when it was replaced ? Had one come in like that, drove me crazy. Finally at wits end, I changed out the MAF to a "known good". Shockingly it solved the problem. No codes were thrown to indicate a bad MAF.

 

[wyelkhunter]

I have not checked vacuum. I tried to clean out the IAC seat as good as I could when I installed the new one. I hope it's not the MAF, those are spendy. I try to clean the sensor in there when I remember, but I can't remember cleaning it too recently. I will do that and check the vacuum too. Thanks for the reply.

 

[dwmmatt23]

Intake manifold gasket, they all get that at some point it seems. Mines does the same just havent changed it yet. Winter comes and its like clockwork, stumbling till it warms up then your good all day, anything below 50 and mine does it.

 

[wyelkhunter]

Huh, I guess I hadn't heard of isues with intake gasket, just the head gasket. I'll look into that.

 

[delta579]

I agree, intake manifold gaskets are a HIGH probability. The VAC test should be reading between 17-20 inches and the needle stable. No jumping around. If it does, then the gaskets are bad. As these engines have very few VAC lines/uses, it's most likely is the intakes.
It's an easy job to to change them out. Just did mine at 152K, took 3 hrs, but I wasn't busting my chops either. Highly recommend changing knock sensors at same time. Plenty of YouTube videos on how to do it the right way.
I couldn't the filth inside the intake !!! I got a gallon of denatured(no stink) mineral spirits(cheap) and poured in a little at a time. Rolled it around in there to coat surfaces then let sit a bit. Drained and repeated numerous times(used whole gallon) until it came out clean. Couldn't believe the coal black gunk that came out ! Now my intake is as clean as new. Don't forget to clean the throttle plate also. Truck runs great, getting 15-18 MPG and I drive it aggressively.

 

[wyelkhunter]

I'll defintely check the vac. That would be great if this could get figured out. Getting sick of the issue. Thanks for the advise!