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2003 Sierra Idle Problem - 2003 GMC Sierra 1500

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EGR valve stuck open or vacuum leaks are a couple of the more common causes of poor idle.

Posted on Apr 10, 2011

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How to change thermostat on 2003 gmc sierra 5.3

Your not going to believe how easy it is to replace this one.

The thermostat is located behind the housing bolted to the water pump that the lower hose attaches to. remove the lower hose from the housing. Remove the 2 bolts holding the housing to the water pump with either a 10mm socket or wrench.

The new stat will come as a stat/housing assembly. bolt it on. Reattach the lower hose. Fill up the reservoir. Let the vehicle idle until up to operating temp making sure to keep the reservoir topped off while the engine warms up.

Mar 03, 2011 | 2003 GMC Sierra

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What and were is the stepper moter 2003 gmc Z71 pick up

If you are talking the IAC, Idle Air Control, it's on the throttle body. It has a 4 wire connector on it.

Mar 02, 2011 | 2003 GMC Sierra 2500HD

1 Answer

2003 GMC Sierra Has recently developed rough idle/lope at idle which sometimes goes away. Runs fine otherwise. Scan codes-Lean condition bank1 and bank2. Random misfires on all cylinders. Fuel pressure...

You never replace anything, on a Wishing,Hoping,Pushing,Poking,diagnostic approach

You learn the vehicles Systems,Test,then Replace,if you have a failed component.

Work on the Misfire Issues.
Then you lean O2 Codes will go away.

Not a the plugs.

Think lean---Vacuum leaks,EGR Valve leak,EVAP System leaks,anything with a hose that lets air into the intake system.
Exhaust System leaks,near sensors

Nov 24, 2010 | 2003 GMC Sierra 1500

1 Answer

I have a 2003 gmc sierra 4.3 was losing spark at idle, tested all modules and cks cms replaced cms in dist still nothing moved through ign module, cks changed as well as coil. still no spaqrk checked fuses...

You may have figured this out already, but I gapped my plugs at gm specs and found out that they changed the plug # and I regapped at 0.40 instead of 0.60 and car ran fine. code finder displayed misfire prior to regapping. Check with Auto parts when buying plugs for car / truck and also make sure that they did not change plug # . These were platium plugs. springfield

Feb 26, 2010 | 2003 GMC Sierra 1500

2 Answers


make sure they sold you the!! right 1 first off! and make sure the wire has continuity to the plug on each and and is securely fastened to the sensor also check to see if you knocked a wire off at the ignition module that controls the dwell

Jan 21, 2010 | 2003 GMC Sierra 1500

2 Answers

Stalls at idle no fluxuation in voltage at iac

It is most likely the EGR (Exhaust Gas Recirculation) valve.
The valve is supposed to close when the car is idling and open other wise.

Inspect it / Replace it.

Hope this helps!

Sep 17, 2009 | 2003 GMC Sierra

1 Answer

Rough/Low idle then dies.

is your check engine light on any longer ? also has your throttle plate ever been cleaned that can cause this symptom it will get build up on it and not allow correct idle ,you can clean it yourself ,rmove the big hose that goes up that goes up to your throttle body and get a can of deep creep sold at any parts house ,then spray the deep creep on a shop rag and by hand wipe out as much of the flap areas as you can ,its hard to get your fingers in there but be patient . but dont spray any thing down in the throttle throat it may cause more problems ,try the wipout of the throtlle area and see if it help your idle !

Aug 08, 2009 | 2003 GMC Sierra 1500

2 Answers

Rought idle then boggs out and shuts off.

I would start with changing the plugs, especially if they are original. If doing yourself, make sure to use anti-seize on threads of new plugs, gap plugs to manufacturer specs, and properly torque plugs to manufacturer specs.
Also, if it has been sitting for a while, change fuel filter, oil, and top off with fresh gas.

May 18, 2009 | 2003 GMC Sierra 1500

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