I have a a 2003 chevy 1500 Z71 5.3 auto i have been having an idle problem The truck will idle at about 750 then will drop to about 300 to 400 then come right back up it causes the truck to die during slow speed manuvers I just had the tranny rebuilt and so i have ruled out the tcc solenoid and any other thing there i have ruled out the crankshaft position sensor cause there is no check engine light on and the truck starts fine i have cleaned the mass air flow sensor and throttle body i have took my K&N filter out and went back to stock i only run non ethonal gas i have checked for bad plug wires when the rpms drop the lights dim and the voltage gauge drops a little any suggestions would be helpful thanks

 

May just need to tighten your throttle cable. Have the DTCs run (autozone and advance auto do it) and bring us back the results (if any).
Also might be a good idea to change your fuel filter.

 

There is no throttle cable its the drive by wire its all electronic from the pedal up also i justed noticed will working on it last night that it only has this problem while the compressor is on like when u got the defrost or a/c on

 

looks like this is your answer:

#04-06-04-040: Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body) - (Jun 14, 2004)
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[/align]Subject:
Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body)
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Models:
2002-2003 Cadillac Escalade, Escalade EXT[/align][align=left]2000-2003 Chevrolet Silverado, Suburban, Tahoe[/align][align=left]2002-2003 Chevrolet Avalanche[/align][align=left]2000-2003 GMC Sierra, Yukon, Yukon XL[/align][align=left]2003 Hummer H2[/align][align=left]with 4.8L, 5.3L or 6.0L V8 Engine (VINs V, T, Z, N, U - RPOs LR4, LM7, L59, LQ9, LQ4) and Electronic Throttle Control[/align]


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Condition
Some owners may comment on an idle instability, low idle speed or rough idle.
Cause
Condition may be caused by deposits in the throttle body bore.
Correction
Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration
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This also sounds like it could be a Idle air control. Unplug the IAC and see if it still does it.

 

i do not think there is an idel air control just throttle position sensor also i have it down to either some sensor not working 100% but enough to keep truck going and not throw light or pcm needs to be reflashed anybody have an idea on cost to get a scan tech 2 test run or to get pcm reflashed

 

88 chevy blazer with a shaking problem in the front!! check out the wheel bearings, brakes and rotors, harmonic balancer, and the clutch fan....

 

02 chevy 1500 5.3 idle about 450 rpm heat in summer over 90 degrees how do I in crease idle speeds