In my previous experience, your car's PCM will not throw a random misfire code unless you are missing on multiple banks within a second of eachother. So normally you look at your factors that pull both sides of the motor together: battery power, fuel, and air.

Starting cheap and easy, my recommendation would be to have your battery tested at a parts store, and make sure your battery connections are solid. You could just have one bad cell screwing things up for the PCM.

Cleaning your MAF is a nice $10 fix... Good idea anyway.

Sometimes it's something stupid like water draining into the gas tank.

Keep us posted!

 

Sorry we could not bring this one home for you. Here's to hoping it's nothing too major.

 

When you say it happens randomly does this mean randomly driving down the road and stopping in traffic or randomly when starting up after sitting for a period of time? If it's the latter I would suspect head gasket. If it comes and goes while driving I would look at MAF & Crank Sensor. I had one at work that had 2 crank sensors (1at crank dampener & the other in back of block) and both were working according to my Tech2. On a hunch I changed the sensor in the block a BAM! just like that it started and ran great. These plastic sensors can have intermittent failures due to heat & moisture.
Good luck.

 

I should have been more specific when I said intermittent. It seems like whenever I do some work on it, it idles just fine and doesn't give me any trouble. Last week I replaced the intake manifold gaskets and cleaned the injectors real good (I removed them from the rail). I put it all back together and went for a half hour long test drive at varying speeds and conditions and it ran great. The idle was smooth as glass. A few hours later, I started it back up to make sure it wasn't a fluke and it still idled perfect. A few hours later, started it again and sure as sh*t, it was idling rough and the check engine light was back on throwing a P0300. I started it a few times throughout the week to see if it decided to fix itself again but no luck. Before last week, it was pretty much hit or miss on start up. Sometimes it would idle good and sometimes it wouldn't. Another thing that happened a number of times is the idle would be very very sporadic and rough, more so then before, and you couldn't get it over 1200 rpms. It would stumble and stall and then wouldn't restart till it sat for a period of time.
Due to the seemingly randomness of this, I'm thinking it's got to be something PCM related. I'm actually about to drop it off at the dealer in just a few minutes. Updates to follow!!!

 

I got a call from the stealership yesterday and they said that it needed a new fuel pump and fuel pressure regulator. I wasn't too convinced that this was the problem due to the fact the fuel pressure at the rail was good but he said the pressure wasn't holding. They wanted $1100 to do the job. I laughed in his face when he told me that and asked when I can pick the car up. I spent $360 for them to diagnose this and I'm just hoping they were right. I just purchased a new pump and regulator from rockauto with shipping for $270. That sure beats $1100!!! Thanks again to everybody for all your help and I'm sure I'll be back when I have the next problem. I'll update as to whether or not the fuel pump fixes the problem. Fingers crossed.

 

maybe it's the fuel injection, the injector may not open properly
can you fix this problem yourself? i hate dealership they overcharge...

 

I hope the dealership was right too. Piece of advice, according to the shop book, you should NOT need to drop the tank to get to the fuel pump. Looks like right behind the rear seat, in the trunk is a bolted in access hatch to service the pump!!

Best of luck, and keep us posted!!

 

It's fixed!! I hate to say it but the dealership was right about it being the fuel pump and fuel pressure regulator. I checked the fuel pressure at the rail and the pressure was good which lead me to believe the fuel pump was good. It was a hard lesson learned but here is what I found out about fuel systems. Even if the pressure is good, which it was, the volume can still be low. Whether that was the cause or not, I don't know. What I also learned, and what was most likely the problem, is there is a check valve in the sending unit and if that gets crapped up, it will return too much fuel to the tank and in my case, caused a random misfire at idle. Chevy did do something right and there is an access panel in the trunk which makes it nice and easy to replace. If anyone else has a hellish random misfire at idle, throw a pump at it. You never know....

Thanks again to everybody for all your help. It's forums and communities like this that keep our hard earned dollars out of the pockets of thieving shops. Cheers. Ken

 

wow, that's great news, thanks for updating your thread with the fix to your issue and all of the us here, hopefully this can help someone in the future.....

 

Thanks for keeping us updated Ken! Glad you have things running right again!!