PI1223

File in Section:
Service Bulletin
Bulletin No.:
Date:
PI1223
April, 2014
PRELIMINARY INFORMATION
Subject:
Black Smoke and Rough Idle on Cold Start
Models:
2011-2014 Buick Regal
2012-2014 Buick Verano
2013-2014 Cadillac ATS
2014 Cadillac CTS Sedan
2010-2014 Chevrolet Captiva, Equinox
2013-2014 Chevrolet Malibu
2014 Chevrolet Impala
2010-2014 GMC Terrain
Equipped with Engine RPOs LAF, LEA, LCV, LTG or LKW
Condition/Concern
Some customers may comment on black smoke, rough idle and minimal misfires on start up only.
This can be caused by the introduction of direct fuel injection systems.
Recommendation/Instructions
A split-pulse injection strategy is utilized during engine cold start to reduce the time required to bring the catalytic
converter up to operating temperature.
This split injection strategy lasts for about 20 seconds on cold start.
This process will cause the customer to see increased black smoke, soot, rough idle, or minimal misfires during cold
start and should be considered normal.
To verify that the split-pulse injection is causing the roughness or misfires with no codes set, you should watch
injector pulse width with the scan tool during the concern.
When in split pulse injector mode operation, the pulse width is about 50% more than a normal idle.
If after 20 seconds the pulse width of the injectors reduces and the engine idle smooths out, this is considered
normal operation and no repairs should be attempted.
If the pulse width on the injectors drops by about 50% and the engine then smooths out, this is considered normal
operation and no repairs should be attempted.
The use of TOP TIER fuels lessens the rough idle condition effects during split pulse injection by reducing the
amount of carbon on valve train components and a more complete combustion leading to cleaner burn.
This cold start strategy is enabled upon start up after the engine has soaked for sufficient time such that the catalytic
converter requires rapid reactivation.