Ended up with two TB's today friend had one. One off a 02 5.3 and one off an 02 4.8 both did the same as the one on the truck.

 

So it's not the TB it's the IAC input to the TB. Either Tune or wiring. What's the IAC voltage that dictates the IAC open to that extreme?

 

I have not checked that but can. Do know that the two wires that are supposed to be hot are and that all four wires are good to the PCM.

 

Tried resetting the IAC?

The purpose of the IAC valve is to control engine idle speed, while preventing stalls due to changes in engine load. The IAC valve, mounted in the throttle body, controls a portion of the bypass air. An orifice located between the throttle valves also supplies a constant amount of bypass air. By moving a conical valve known as a pintle (3) in toward the seat, to decrease air flow, or out away from the seat, to increase air flow, a controlled amount of air can be bypassed. If engine speed is too low, more air is bypassed in order to increase RPM. If engine speed is too high, less air is bypassed in order to decrease RPM. The PCM moves the IAC valve in small steps, called counts. These can be measured and displayed with a scan tool, which plugs into the data link connector (DLC). The PCM calculates the proper position of the IAC valve during idle based upon the battery voltage, the coolant temperature, the engine load, and the engine RPM. If the RPM drops below specification and the throttle valve is closed, the PCM senses a near stall condition and calculates a new valve position in order to prevent stalling.

• Engine idle speed is a function of total air flow into the engine. Idle speed is based on IAC valve pintle position, crankcase ventilation valve flow, throttle valve opening, bypass orifice air flow, and calibrated vacuum loss through accessories.
• Controlled idle speed is programmed into the PCM, which determines the correct IAC valve pintle position to maintain the desired idle speed for all engine operating conditions and loads.
• The minimum idle air rate is set at the factory with a stop screw. This setting allows enough air flow by the throttle valves to cause the IAC valve pintle to be positioned a calibrated number of steps, counts, from the seat, during controlled idle operation.
• If the IAC valve is disconnected and reconnected with the engine running, the idle speed may be wrong. If this occurs, reset the IAC valve by depressing the accelerator pedal slightly, starting and running the engine for 5 seconds, and then turning the ignition OFF for 10 seconds.

 

^^^sounds like a winner...

 

Now this is the kind of info I am looking for. First thing THANKS A LOT DRX

 

Did not help at all

 

Drove the truck today had the exhaust put on boy did I mess up with the mufflers way to loud way. Used pipes violators they are coming back off tomorrow. Tried driving it with the IAC plugged did not help any. Truck runs very good just need to get the idle fixed.

 

What do you mean by plugged?

Are the tune, PCM and your truck all of the same model year?

Were any of the idle parameters altered from stock in your tune? If a "compare" shows no changes, and everything else matches up, then there is extra air getting in somewhere.

 

What do you mean by plugged? : Plugged in the IAC

Are the tune, PCM and your truck all of the same model year? : Nelson is doing the tuning and I would think they are the same year.

Were any of the idle parameters altered from stock in your tune? If a "compare" shows no changes, and everything else matches up, then there is extra air getting in somewhere. : If the next tune he is sending dose not take care of it I am going to pull the blower back off and get a real long and good look at the intake and see if I can find anything wrong there. With the IAC unplugged it idle's fine but you plug it in and it will go right to 2000 ever time. I have a new gasket setting here so if I have to pull it I can.