This is annoying the heck out of me. I have recently done the Hahn stage V turbo conversion and everything is great except 1 thing.... I am tripping the cel code P0300(Random cylinder misfire). It is soo annoying because when the car is at idle it sounds like im constantly giving it gas and its reving up/down constantly non-stop. I know alot of balt owners say that running 60lb/hr injectors this problem just happens but in my situation its terrible. Im even stalling alot when I come up to a stop sign for instance and it could become a very serious issue some day because if Im listening to tunes and driving I go to pull across an intersection and nothing!! Car is just dead so I have to start it up again and usually takes a few seconds. This is not good. I talked to Aaron @ Hahn and they are going to work with me to try to help correct this issue but we just had to wait because I didnt have hptuners yet(coming on Monday) at that point I hope we can figure something out because its not only annoying but like I said, it could become very hazardous some day. I hope we can fix this problem asap as there has got to be a way to do this. I dont buy alot of balt owners just "Accepting" this issue. We need a fix and sooner than later preferably..

 

damn i have the same code come up but just the lights is on and all but car runs good

 

Found this old post..hope it helps.

Subject: Engine Misfire Due to Injector Control Circuit Short on AC Line Bracket - keywords accelerate acceleration drive gound load loss miss no P0200 P0201 P0203 P0204 P0300 P0301 P0302 P0303 P0304 under #PIP3536 - (09/08/2005)



Models: 2005-2006 Chevrolet Cobalt SS

2004-2006 Saturn Ion Redline

Addition I think it explains it better

Condition/Concern:
Some customers may comment on a severe engine misfire and a SES Light. Upon inspection, DTCs P0300 - P0304 may be found due to misfires on cylinders 1 and 4 or cylinders 2 and 3.

Recommendation/Instructions:
If this concern is encountered, inspect circuits 406 (IC Control for 2/3 Coil) and 423 (IC Control for 1/4 Coil) for an intermittent short to ground or poor connection on either end. Depending on the model, these circuits may short on the AC lines near the AC compressor, on the transmission mount, or on the transmission lines where they enter the transmission. If there is no problem found with these circuits, inspect the ignition control module ground to ensure that it is clean and tight ignition control module may also need tested.



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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
On rare occasions, a SES Light and engine misfire may be experienced due to a chaffed injector control circuit. As a result, any of the following DTCs may be stored: P0200, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, or P0304

Recommendation/Instructions:
If the SI diagnosis does not isolate a cause for the concern, inspect the fuel injector harness for a potential short to ground at the air conditioning line bracket at the rear of the head, above the transmission. If signs of a short to ground are present, repair and reposition the circuit/harness as necessary.


Subject: SES Light On or Various Driveability Concerns - keywords backfire cold DTC G103 hesitate idle INT intermittent light low MIL rough stall start SES various warm #PIC3457A - (12/07/2005)



Models: 2005-2006 Chevrolet Cobalt

2005-2006 Pontiac Pursuit




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A customer might comment about a SES light on or Various driveability concerns intermittently.

Recommendation/Instructions:
The first thing to check is Ground G103 for it being loose, If it is tight then proceed with current diagnostics.

Note: This ground is located behind the left front head light assembly on the top of the frame rail.

Found this as well
02-06-05-004b Info - Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due to Installation of Alarm Systems - (Feb 14, 2006)

Another

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Subject: Cylinder Miss On Left Turns And Cylinder 4 Miss On Right Turns - Possible Fuel Contamination - keywords CEL contaminated controls cylinders gas injector intermittent MIL misfire P0300 P0301 rail rust #PIP3333A - (07/12/2007)



Models: 2004-2008 Chevrolet Aveo

2004-2006 Chevrolet Cavalier

2005-2008 Chevrolet Cobalt, Cobalt SS

2006-2008 Chevrolet HHR

2004-2008 Chevrolet Malibu

2007-2008 Pontiac G5

2006-2008 Pontiac G6

2005-2006 Pontiac Pursuit (Canada Only)

2004-2006 Pontiac Sunfire

2003-2008 Pontiac Vibe, Vibe GT

2003-2008 Saturn Ion, Ion Redline

2007-2008 Saturn Aura, Aura Hybrid

2004-2008 Saturn Vue

2007-2008 Saturn Vue Hybrid

with a 4 Cylinder Engine

(RPOs L61, L91, LAT, LE5, LNK, LSJ, LV6, or LXT)




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This PI was superseded to update models. Please discard PIP3333.


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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
On rare occasions, an intermittent engine misfire may be experienced on cylinder 1 during/following a left turn or on cylinder 4 during/following a right turn. The misfire may / will typically last up to 10 seconds. A SES light and DTCs P0300, P0301, and/or P0304 may also be present if the misfire lasts long enough.

This may be the result of fuel contamination and is more likely to occur on vehicles with a returnless fuel rail because it is easier for fuel contaminates to become trapped in a returnless fuel rail since they do not have a fuel return line that returns fuel back to the fuel tank. As a result, any fuel contaminates that make it to the fuel rail tend to gather over the #1 fuel injector inlet when turning left and tend to gather over the #4 fuel injector inlet when turning right, causing this concern. The cylinder next to the fuel feed line (1 or 4 depending on the model) may also experience some random misfires at idle as contaminates enter the fuel rail from the fuel tank.



Another one I read:
Missfires caused by aftermarket alarm systems due to the mechanical relay they use in there unit for disarming the car.

Heres some stuff to check

1)Operate the engine at idle.
Observe the Heated Oxygen Sensor (HO2S) parameters with a scan tool.

2)Visually and physically inspect the following items:
The vacuum hoses for splits, kinks, and proper connections

3)Inspect for the following conditions:
The HO2S for proper installation
Ensure that the electrical connectors and wires are secured and not contacting the exhaust system.

4)Inspect for the following conditions:
-Missing, loose, or leaking exhaust components
-Vacuum leaks at the intake manifold, throttle body, and injector O-rings
-The air induction system and air intake ducts for leaks
-The crankcase ventilation system for leaks
-The evaporative canister purge pipes for obstructions or plugging.

5)Still could be your Maf
Observe the manifold absolute pressure (MAP) sensor pressure parameter with a scan tool.

Worst case
6)If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be at fault.

7)Test for fuel contamination. Small amounts of water can be delivered to the fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

8)The system will go lean if an injector is not supplying enough fuel.

9)A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel, a plugged fuel filter, or a restricted fuel pipe.