Marky Dissod
Full Access Member
Not yet, but I'm about to take it off the engine, take the IAC motor & throttle sensor off, and clean the ever-lovin schidt out of everything thrice.
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his has a IAC idle air control valve, which is what controls the idle primarily mechanically anyway, the 00-02 had them with drive by cable, previous years probably did as well as egr, in 03 they went to drive by wire with a fully electronic idle control (single piece unit),What about the TPS ? Throttle position sensor??? maybe that could cause this.
Cold starts require a rich fuel mixture (aka choked). You may not be old enough to remember carburetors and automatic chokes and before them manual chokes. In fuel injection to obtain a "choked" condition the on time is just increased on the injectors. In carbs they just mechanically shut the butterflies until the engine warmed up.You may very well be right. Although I've never understood why, 'arctic' cold starts correlate with higher RpM starts.
If the engine somehow thinks it's even colder than it actually is, that could be one possible explanation.
I'll find a mech to provide me with the temp sensors' readings later this week.
Hoping for @rockola1971 's counsel.
Not trying to be THAT guy, but the more likely culprit would be that the pintle is restricted from closing quick enough after start up. With the added fuel of the cold start enrichment based off the coolant temp adder, the truck would rev high if the pintle was stuck more so outwards away from the seat, than in. It's easy to get that backwards if you picture the the airflow working like a carb by increasing the venturi draw on the nozzle by restricting air flow. In the case of efi, they are two independent functions, so you add more idle air to go along with the extra fuel added via the injector enrichment.Cold starts require a rich fuel mixture (aka choked). You may not be old enough to remember carburetors and automatic chokes and before them manual chokes. In fuel injection to obtain a "choked" condition the on time is just increased on the injectors. In carbs they just mechanically shut the butterflies until the engine warmed up.
I would pull your IAC and see if the pintle is caked with carbon deposits. Large chunks can get wedged behind the pintle which doesnt allow the pintle to fully travel retracted. Brake cleaner instantly dissolves this carbon. LS engines are notorious for intake manifold gasket leaks so spray around the manifold sealing areas with ether or the like and see if idle jumps. If it does then you found the leak. A bad engine coolant temp sensor could cause your problem too. If PCM doesnt see the engine warming up it will try to run in choke mode too long.
The carbon restricts or completely stops the pintle from moving depending on where it gets wedged. It can wedge between the pintle and the inner bore of the IAC or behind or in front of the pintle reducing or completely stopping any movement inward and outward. This was a very common problem in the 2.8 V6 engine years ago. And high idle or rough idle was the symptom.Not trying to be THAT guy, but the more likely culprit would be that the pintle is restricted from closing quick enough after start up. With the added fuel of the cold start enrichment based off the coolant temp adder, the truck would rev high if the pintle was stuck more so outwards away from the seat, than in. It's easy to get that backwards if you picture the the airflow working like a carb by increasing the venturi draw on the nozzle by restricting air flow. In the case of efi, they are two independent functions, so you add more idle air to go along with the extra fuel added via the injector enrichment.