Morning Start Problems

[kc5deb]

I have a 2002 GMC 2500 4x4 with the 6.0L and has 115,000 miles on it. Only upgrades have been a wait4me tune, and a flowmaster 80 series.

 

It doesn't always do this, but, it's more apparent on cooler mornings. I go outside to start it so as to warm it up before I put my cold natured self inside. It starts fine, but, the rpms drop, it chugs, sounds like it's running on only half the cylinders, then dies. I'll start it again, and sometimes, it does it over 2-3 times before it stays idling. It never has thrown any codes to date.

 

I've got a few things in mind to try, but, before I start throwing $$$ away, I figured I'd ask here first.

 

PCV valve going bad? Easy way to check this?

 

Fuel pump going out? Hope not, cause they're expensive, but, never had fuel related issues, and nothing else is tipping my hat to this.

 

Fuel filter is fine; just changed it 4 months ago.

 

I changed the spark plugs less than a year ago

 

O2 sensors failing? I get horrible mileage (15 on a great day downhill with the wind to my back driving 65mph, and average about 12-13mpg with town driving). Although it is a 2500 4x4 supercab with the 6.0...

 

Cats getting clogged? again, hope not, cause not in the mood to chunk a ton of money at it around the holidays.

 

Intake gasket starting to fail? Any good way to test for this too?

 

Seems like it doesn't have all the power it used to. Still runs like a raped ape, but, not quite as quick as what I once remember.

 

Any hints are well appreciated.

[green 788]

Maybe try cleaning the intake plenum... could be carboned up and causing some issues.

 

There is (I assume) a mass airflow sensor that might be giving trouble. Many of these parts can be picked up from a junkyard for about 20% of what the dealer charges. Then if it doesn't fix the problem, you presumably have a spare on hand for the future, if needed.

 

Throttle position sensor may be going bad, causing the computer to lose input and not know it's supposed to be idling.

 

If it's just a cold morning issue, you could try this: Use a blow dryer to heat up the suspected bad sensor for a minute prior to starting the truck. If the problem does not present after heating the mass airflow sensor (for example), then that could be your problem...

 

And by the way, I'm not a GM technician but I did stay at a Holiday Inn Express last night. ;)

 

Good luck.

 

Dan