icemaid

iTrader: (1)

I have cleaned the MAF and air filter and installed new O2 sensor, what should i check next? I dont even bother to clear the code because it comes right back on.

07 ss/sc, 2.8 pulley, 60lb injectors, i step colder plugs, injen intake, 3" stainless exhaust

rnjmur

Check the coils and plugs.

red06s/c

ah same problem as me, i didnt have it until i changed from 42's and a 2.9 to 60's and a 2.7. dude that tunes my car said he will look at it again, guessing it may be a tune related problem?

Pyros777

iTrader: (4)

Is it only P300, or do any other cyl-specific misfire codes come up?

Definitely check your coils and plugs and report back.

red06s/c

with my car it only shows a p300 on my interceptor with another cat-code but i know what that is.

icemaid

iTrader: (1)

not cyl specific, just the random misfire, ......pain in the butt!!!! Will be taking it in to shop to be scanned by them, was just hoping to take care of it myself.

Pyros777

iTrader: (4)

When I had a constant random misfire, it turned out to be a frayed wire leading to coil #4. It was making contact with the block. Every time it would touch, it'd misfire, the misfire would jossle the motor, causing the wire to touch again, and again, and again, it was hell. lol

red06s/c

i know this isnt my thread and sorry to the OP, but any idea what would cause it to happen only after a new tune? I never got this code until i have the car retuned for the new injectors and pulley.


After searching some ive found a thread that says it could be the frequency of the MAF needs changed, or they says its running lean. Here is the thread.
https://www.cobaltss.net/forums/show...highlight=p300

MP Cobalt

iTrader: (4)

I have this same code. People were saying before the light weight flywheel would cause it. Now i need new plugs or someting now?

icemaid

iTrader: (1)

I didn't have this problem until about 4 months ago, dont think its my tune as i had the tune done about 1.5 years ago.

Pyros777

iTrader: (4)

Sounds more related to the injector install rather than the tune. Have you tried reverting back to your old injectors/tune to see if the problem persists?

red06s/c

no i havent tryed that. The car runs fines, like it only has a slight rough idle at idle. never tryed to stall or anything so i might just say screw it and drive it lol. My tuner said 60's dont idle real smooth so i just thought it was related to that but i donno.

icemaid

iTrader: (1)

No i haven't. I don't have the stock injectors anymore. I've had these injectors/pully/tune for 1.5 years, if anything maybe it is an injector going.

MP Cobalt

iTrader: (4)

mine started happening like 3 months ago i clear it and drive like 5 miles and it pops back on.

insylem

I get P300 every time i scan with my interceptors.
I unplug my intercetpors,
and I can scan PASS no codes.
If I set interctetpr to watch misfires
after a few minutes i get a CEL with P0300

Somehow I thnk my interceptors are
CAUSEING mine to randomly think its misfireing.

FOr the most part I dont get the light thogh.
Unless I go to the misfire pages.
Or if I sit and idle for a really long time.

rnjmur

It is common to get misfires with 60s, but you shouldn't throw a code. It is possible that if the injectors weren't tuned right it could throw this code. Checking the plugs and coils is an easy first thing to check before starting from scratch with the injector tune.

Coblasts

Check the injector harness for damage or bare wires,

MP Cobalt

iTrader: (4)

Well the wires are bare on the 60# lb harness near where they plug into the injectors. maybe the heat is getting to that wire there and causing the code to pop on? My car has the code all the time anymore but it still runs fine?

icemaid

iTrader: (1)

Just got back from the shop where they scanned it........catalytic inefficiency code

mrw5641

I know this is an old thread. how do you check for bad coil packs?

insylem

Swaptronics.
Just swap the suspected bad one to a different cyldiner. See if misfire follows. Doesnt really work for P300 though but normally if you have a bad coil pack youll get P301 or 302 ect for whichever cylinder is bad.

riceburner

iTrader: (66)

i was getting the same code even after re-replacing my plugs. now its been gone for a while? wierd.

same mods as op basically, could be a tune thing for me idk... car seems to run fine

mrw5641

I just think the computer isn't telling me what coil is wrong. I mean it seems to be a random ghost p300. The rpms jump up and down and settles. BUt besides that it runs fun. Just gotta test the coils idk an easy way