Mechanics

CHEVY ROUGH IDLE - CODES P0151, P0174, P0300

2005 Chevrolet Tahoe

Engine Performance problem
2005 Chevy Tahoe V8 Four Wheel Drive Automatic 66650 miles

Tahoe is running very rough at idle, almost stalling. Check Engine light is on, Onstar Diagnostic says to have car serviced, emissions control error. Actuall codes are P0151, P0174, P0300. Replaced plugs (AC Delco), Wires, and new Interstate battery. Added fuel injector cleaner. Only 66650 miles, passenger side plugs were all fouled, driver side normal deposits. Still running rough with " rotten egg" smell from tailpipe at idle. Runs fine at speeds above 20 mph.

Any suggestions before I bring to dealer? Warranty is no longer valid, but have a engine and transmission warrantly thru original dealer in CO, vehicle in WY.
Avatar
Dwilson39
January 5, 2009.




Here is some info: LM7, L59 or L33 Engines with Cold Start Rough or Incorrect Idle, Misfire, Malfunction Indicator Lamp (MIL) or Flashing Requiring O2 Sensor Replacement (Reprogram PCM)

Models: 2004-2005 Cadillac Escalade

2004-2005 Chevrolet Avalanche, Silverado 1500, Suburban, Tahoe

2005 Chevrolet Silverado Hybrid (HP2)

2004-2005 GMC Sierra 1500, Yukon, Yukon XL

2005 GMC Sierra Hybrid (PH2)

with Vortec 5300 5.3L V-8 Engine (VINs T, Z, B -- RPOs LM7, L59, L33)

Some customers may comment on a Malfunction Indicator Lamp (MIL) On or that the MIL is flashing. An actual engine misfire may or may not be felt along with an incorrect idle speed. Typically this occurs during cold winter months, on cold engine starts. Some vehicles may have been previously serviced for the same condition. Technicians may also find the following DTCs stored with the Tech 2 P0131, P0133, P0134, P0137, P0138, P0140, P0151, P0153, P0154, P0157, P1133, which may be in conjunction with P0171, P0174, P0300 and P1138.

Cause
Water shock occurs when water droplets are present in the exhaust. The water in the exhaust contacts the sensor element inside the HO2 sensor, causing the HO2 sensor element to crack.

Correction
Upon diagnostic investigation, the technician may find that the HO2 sensor requires replacement. In addition to replacing the affected HO2 sensor, these vehicles should also be reflashed with the latest PCM calibration. Important: If a DTC P0420 or P0430 is stored along with DTC(s) P0300, the catalytic converter diagnostics in Service Information (SI) must be followed to determine if the catalytic converters are operating properly.

There is a good chance the cat converters got damaged from the missfire. Post back with any other questions and what you find.

Brian 1
Jan 5, 2009.


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