I have a 2002 LT Tahoe 4x4 with ~101,000 miles.
5.3L V8 engine (flex fuel capable)

Here lies my problem. When the vehicle sits over the night during the winter, it has troubles wanting to run correctly until the engine reaches it's operating temperature. Upon start it initially holds a higher RPM at idle, which I expect, but once the idle RPM's drop below 1000, it starts to pulse as it idles. The RPM's seem to drop ~200 during each pulse. Each pulse happens on 3-4 second intervals. Once in gear, the vehicle's resting RPM seems to stick around 1100. I can typically cruise close to 30 mph without touching the accelerator. The vehicle wants to lunge through my braking making it troublesome when approaching vehicles and stop signs. Sometimes the service engine soon comes on and will stay on for a day or two, sometimes the service engine soon light will flash ~12 times and go off. I have had the code read once and it was P0174. Also, the interior blower motor works great, but the vehicle doesn't put out heat unless the temp control is fully turned clockwise (until the **** clicks).

Any help is appreciated with where to start! Thanks you.

 

You need to look at low fuel pressure. 10psi low would cause problems for a cold engine but would still run a warm engine. Also you need to look at the coolant temp sensor reading. If it thinks the truck is already warm then the computer would not provide enough fuel. The 5.3 is also prone the intake gasket problems that only occur cold.

 

Thanks for the advice. I was hoping for a do-it-yourself easy fix, but I guess I'll have to have a shop look at it. I'll be sure to keep those ideas in mind once it's looked at. Any idea what a shop would charge?

 

The engine is running rough, either just at idle or also during acceleration. Look at the FAQ's for rough idle and engine shaking problems for your specific symptoms.
The gas cap hisses because the air is coming out it was trapped under pressure. That is normal when your tank is less than half full which would also be the time you take the cap off to put gas in. Hope this helps!






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He probably needs a coolant temp sensor. Maybe clean maf.
But he probably done has it fixed.

 

Second for intake manifold gasket sucked in. Will cause your cold rough run and low coolant and irratic temp for other concern.

PBJT

 

Where you able to fix your low temp problem? I've got a 2003 Tahoe with the same problem.