2014 SS Rough Idle, Service Stabilitrak

[Gordy87]

Originally Posted by SSMickey

If your engine is an L99, I'll bet you have a collapsed AFM lifter. Check your code and misfire data stream. The AFM lifters are on 1, 4, 6 and 7. If the misfire is one of those cylinders, pull the valve cover and have some one crank the engine and watch the rocker arms. If you see a rocker arm not moving, you just found your problem.

Yea. What a B!@$#. Replaced them twice in me "09 Hoe" after 1 of the new ones collapsed less than 4 months later. Thats why I purchased a Range Device from a member and installed.

[0-120]

P0300 Random/Multiple Cylinder Misfire Detected

[cypressh]

that sounds like mechanical failure somewhere in the valve train. pull the valve covers and take a look.

[RedRyder]

I've seen these exact symptoms with my car a few times. Slow crank, check engine, stabilitrak, rough idle, no power, and random cylinder misfire code. People say weak battery but what it really it is a weak crank (that can be caused by a weak battery). If you're still slow cranking after a new battery then I would suggest replacing the starter.

With these cars, if the engine turns over too slowly, like just enough to get the engine going, it causes these exact symptoms.

Could still be something mechanical but what you're seeing is too similar to what a lot of us have seen when the engine just cranks too slowly but still manages to fire up. Good luck!

[29er]

Conditions for Setting the DTC


DTC P0300


Circuit/System Description

The engine control module (ECM) uses information from the crankshaft position sensor in order to determine when an engine misfire is occurring, and uses information from the camshaft position sensor in order to determine which cylinder is misfiring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets. Under certain driving conditions, a misfire rate can be high enough to cause the catalytic converter to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) will flash ON and OFF when catalytic converter overheating conditions are present and DTC P0300 is set. DTCs P0301–P0308 corresponds to cylinders 1–8. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will also set.



The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards or a misfire rate high enough to cause catalyst damage.
Action Taken When the DTC Sets

•DTCs P0300–P0308 are Type B DTCs.


•When the MIL is flashing the fuel injector may be disabled for the misfiring cylinder to protect the catalytic converter.


•Depending on the conditions that set the DTC, the engine may go into Open Loop.

Diagnostic Aids

•Ensure that each fuel injector is connected to the proper fuel injector harness connector. Refer to Engine Controls Schematics


•A high resistance condition on any fuel injector control circuit can cause an engine misfire P0300–P0308 DTC to set without setting a fuel injector circuit P0201–P0208 DTC.


•A high resistance condition on any ignition control (IC) circuit can cause an engine misfire P0300–P0308 DTC to set without setting an IC circuit P0351–P0358 DTC.


•A misfire may only occur when the engine is operating under a load or when the engine is cold.


•A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect the following for possible sources of vibration:


◦A tire or wheel that is out of round or balance


◦Variable thickness brake rotors


◦An unbalanced drive shaft


◦Certain rough road conditions


◦Transmission operation


◦A damaged accessory drive component or belt; remove the belt and safely operate the engine to evaluate


◦A damaged reluctor wheel




Circuit/System Testing
1.
Verify none of the following conditions listed below exist:


◦Damage, carbon tracking, or fluid intrusion of the spark plug boots and/or spark plugs


◦Vacuum hose splits, kinks, and incorrect connections


◦Engine vacuum leaks


◦Crankcase ventilation system for vacuum leaks


◦Fuel pressure that is too low or too high. Refer to Fuel System Diagnosis.


◦Contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.


◦Exhaust system restrictions. Refer to Restricted Exhaust


coolant in cyl may cause this also.
the p0300 as posted is for all cylinders.

[0-120]

Update:

The issue was a broken pushrod & valvespring. Replaced these, got a CAI and a dynotune.

After a week of driving (in excess of 500 miles) I have gotten a code P0430.

Catalyst System Efficiency Below Threshold Bank 2

Does this mean the cat is gone? What are my options?

[Hulk]

You state you just got a dyno tune. I would contact the tuner and see what they say? It might possibly be something in the tune causing a rich or lean condition.