Rough Idle in Gear

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camperhead

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When i put 03 Tahoe in gear and sitting still (like at a red light) truck has a vibration and engine is at about 500RPM. Sometimes it sounds like its going to stumble and die but hasn't... Any ideas?? OH no codes or otherwise loss of performance

---------- Post added at 01:08 PM ---------- Previous post was at 12:58 PM ----------

Forgot to mention that I have already done a tune up( new OEM plugs and wires, Fuel filter) And cleaned MAF
 
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camperhead

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Last night I cleaned MAF and throttle body, also did a crankshaft relearn, hooked up to my brother-inlaws new snap-on scan tool. NO codes still, no logged misfires, also watched the o2's both pre cat sensors are switching from a low value(50) to a high (700-800ish) back and forth, the post sensors are staying at a high (700ish)..
 

PUGLIA

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It's the pcv valve. Mine did the same thing. Go to orielys and get a fixed orifice pcv valve. You'll need to ask for a pcv valve for a 03 to 06 tahoe. The 00-02 had a spring and ball pcv valve that screws up. You'll know it's a fixed because it will be flat on the bottom with a little pin hole. The 02-03 have a wide hole with a ball and spring that rattle. The fixed does not rattle. Should solve the problem.


-----PUGLIA-----
 

PUGLIA

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Sorry man it wasn't the pcv valve that was the supposed fix its the plug on the tv plate that I've been wondering about.
And this:

Increased Accelerator Pedal Effort, Idle Instability (Clean Throttle Body and Adjust Blade) #02-06-04-054B - (03/17/2003)

Increased Accelerator Pedal Effort, Idle Instability (Clean Throttle Body and Adjust Blade)
1999-2002 Chevrolet Silverado

2000-2002 Chevrolet Suburban, Tahoe

2002 Chevrolet Avalanche

1999-2002 GMC Sierra

2000-2002 GMC Yukon, Yukon XL

with 4.8L or 5.3L V8 Engine (VINs V, T, Z -- RPOs LR4, LM7, L59)

This bulletin is being revised to add condition information. Please discard Corporate Bulletin Number 02-06-04-054A (Section 06-Engine).

Condition
Some customers may comment on an idle instability and/or a higher than expected accelerator pedal effort from the idle position.

Cause
Condition may be caused by deposits in the throttle body bore and on the throttle plate.

Correction

Important
This procedure only applies to cable actuated throttle bodies on the models listed above. This procedure should not be performed on electronically controlled throttle bodies or on any vehicle or engine that is not listed above in the Models section.


Verify that the cause for this condition is not a damaged or binding throttle cable.
Remove the air intake duct. Refer to Air Cleaner Duct Replacement.
Inspect the vehicle for installation of a fixed orifice PCV valve, refer to Corporate Bulletin Number 01-06-01-029B for PCV valve identification. Vehicles undergoing this throttle body procedure MUST use a Fixed Orifice PCV Valve, P/N 12572717.
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.
Select the correct plug for the size of the air bypass hole in the throttle body being serviced. Use a 1/8-inch (.125") drill bit to determine which plug to use.
Vehicles built before introduction of the Fixed Orifice PCV Valve will have a 3.75 mm (.150") air bypass hole in the throttle plate. The 1/8-inch drill bit is smaller than the air bypass hole in these throttle bodies and can be inserted into the bypass hole. To plug the air bypass hole in these vehicles requires the yellow plug, P/N 12580749.
Vehicles built after introduction of the Fixed Orifice PCV Valve will have a 2.6 mm (.104") air bypass hole in the throttle plate. The 1/8-inch drill bit is larger than the air bypass hole in these throttle bodies and cannot be inserted into the bypass hole. To plug the air bypass hole in these vehicles requires the red plug, P/N 12581011.

Insert the appropriate plug (1) into the air bypass hole in the throttle plate. Insert the "tail" end of the plug through the throttle plate air bypass hole.

Open the throttle plate to allow access to the tail end of the plug. Pull the tail section to securely position the plug into the air bypass hole and trim excess material (1) from plug.
Turn ignition key to the on position, with engine off.
Use the Tech 2 Scan tool to read initial TPS voltage.

Important
TPS voltage cannot exceed .69 V. If the vehicle has an initial TPS voltage greater than .61 V, replace the Throttle Body Assembly. This part is currently on parts restriction. Contact the General Motors Powertrain Quality Center at 866-654-7654 for assistance.


Using the Tech 2 Scan tool and a T15 driver to rotate the Minimum Air Rate screw, increase TPS voltage by .08 Volts (Refer to TPS Voltage Chart below).
Turn ignition key to the off position. Verify that the accelerator pedal moves freely - Depress the accelerator pedal to the floor and release.
Install the air intake duct. Refer to Air Cleaner Duct Replacement.
Start engine.
Using the Tech 2 scan tool, monitor TPS voltage and verify the TPS voltage is no greater than 0.69V.
Road Test Vehicle.

Important
If an increased accelerator pedal effort condition still exists after performing this bulletin, throttle body replacement may be required. Please contact the General Motors Powertrain Quality Center at 866-654-7654 for assistance, as the throttle body is currently on a parts restriction program.

If initial TPS voltage is greater than .61 V Replace Throttle Body Assembly

Parts Information



Part Number 12580749
Description Plug, Throttle Plate - Yellow
Qty 1

Part Number 12581011
Description Plug, Throttle Plate - Red
Qty 1


Parts are currently available from GMSPO.


-----PUGLIA-----
 

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