2011 Camaro 2SS suddenly running rough

[wjalex4]

2011 Camaro 2SS w/automatic transmission. "J" code car. About 120,00 miles. We've owned the car for about 4 years now... it's always been reliable.

Last week, out of the blue, when we started the car it idled rough and would barely make it down the road. We turned around and brought it back home. I always do all my own auto repairs, but I am stumped.

Check Engine light came on - I had a P0300 Multiple Cylinder Misfire code. That was the only code. I pulled all plugs today (only about 10,000 miles on these AC Delco plugs), and they seemed fouled. I cleaned and checked the gap (gap OK), and put them back in. I carefully checked all plug wires too. Seemed okay (also about 10K miles on the plug wires).

The car started and ran better, but still rough. I cleared the P0300 code. A new code, "P0174 System too lean bank 2" appeared, followed by the return of the P0300. I checked the fuel pressure using the port on the fuel rail - 60 psi consistently, with key on before starting and while running.

Checked the battery, and it was at 12.13V with car off, 14.78V while idling rough. The battery came from O’Reilly and is the Super Start Extreme model. It’s 3 years 2 months old.

I am really stumped. Any ideas would be very much appreciated. Thanks.

[joshnmn]

That battery voltage is a bit low. Looks like the alternator is trying to charge. Might be time for a new battery. You said it’s 3 years old. Is that 3 years of use, or as a weekend cruiser?

[Hetfield03]

Dang. I got the p0300 code last Saturday myself along with 03 and 01. Hasn't come up since though. Will be following this thread for sure.

[wjalex4]

I will go get a new battery this morning. Thank you!

[wjalex4]

I replaced the battery but unfortunately the problem did not change. After that, I used my inductive timing light to ensure that all eight coils were generating spark to their respective plugs in a consistent fashion. I have wiggled and jiggles all the wiring harnesses and connectors I could find under the hood, all of which made no difference. The ground connection from the battery to the floor in the trunk is super-tight, and there is no rust or corrosion.

I have just uploaded a video of the car starting a running, which I hope may lead to some ideas of what the issues could be. Here is the link:

https://drive.google.com/file/d/1P6U...ew?usp=sharing

If anyone has trouble accessing it please let me know. Thank you - Walter

[redcoats1976]

my buddies 2015 V8 was running rough,turned out to be dirty injectors only 60,000 miles on it.just a thought...

[ABM2SS]

my buddies 2015 V8 was running rough,turned out to be dirty injectors only 60,000 miles on it.just a thought...

Yep, could be a bad tank of gas.

[acutron42]

Originally Posted by ABM2SS

Yep, could be a bad tank of gas.

My L99 acted like this & I put in a bottle of K100 for a quick cheap test. I cleaned the mass airflow sensor @ the same time & it cleared right up. Start with the cheapest & easiest solutions 1st. What tool did you use to pull the codes.

[1JEWLDSSRS]

Originally Posted by acutron42

My L99 acted like this & I put in a bottle of K100 for a quick cheap test. I cleaned the mass airflow sensor @ the same time & it cleared right up. Start with the cheapest & easiest solutions 1st. What tool did you use to pull the codes.

Yep, could be a bad tank of fuel. I use the Lucas fuel injector cleaner in the small white/clear bottle in mine every oil change. Keep the injectors clean, plus as mentioned, you may have a dirty MAF.. Good luck..

[Moto-Mojo]

I'm no daisy but I'm leaning toward bad gas, bad/dirty MAF, bad MAF connection. I had some much milder hesitation issues that somehow 'fixed' themselves. (my favorite kind) That would tend to point toward bad fuel. TEND...being the operative word.

[wjalex4]

Thank you everyone. I've got about 1/2 a tank of gas, and I always fill it. That would mean that I ran fine on the first 1/2 tank, then suddenly the gas was bad. I will start by cleaning the MAF tomorrow and checking the MAF connections. I will report how that goes.

Thank you everyone!

[acutron42]

Here is some info from Alldata. There are 44 results on this issue & too much to post. It could be a faulty crank position sensor but without seeing comprehensive scan data I would start with the basics. The maf sensor & fuel quality are low on the list in other sections but rule these out first as they are worth exploring for ease & cost.

DTC P0300

The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards.

DTC P0301, P0302, P0303, P0304, P0305, P0306, P0307, or P0308

The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

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.

Conditions for Clearing the MIL/DTC

* DTCs P0300-P0308 are Type B DTCs.

* The DTC must run and pass under the same operating conditions that were present when the DTC failed.

Diagnostic Aids

* The Crankshaft Position System Variation Learn procedure may need to be performed. Refer to Crankshaft Position System Variation Learn See: Crankshaft Position Sensor > Programming and Relearning > Crankshaft Position System Variation Learn.

* Ensure that each fuel injector is connected to the proper fuel injector harness connector. Refer to Engine Controls Schematics ((L99/LS3)) See: Powertrain Management > Electrical > Engine Controls SchematicsEngine Controls Schematics ((LSA)) See: Powertrain Management > Electrical > 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.

[wjalex4]

The car is fixed! The problem was a dirty MAF sensor. I cleaned the sensor using cleaner design just for those, which I had on the shelf from another car repair a decade ago. I carefully removed the MAF sensor and cleaned it really good using the spray and then let it dry and then reinstalled it and the car started up and idle perfectly ran it up and down the road up to about 90 mph and it did great. Thanks so much everyone!

[Hetfield03]

Sweet! I'm gonna clean my maf sensor before I change out my coil. And plugs are less than 2 years old.