great421

iTrader: (1)

My $0.02 -

(This code happened to me last week)

Get a stethoscope and listen to each and every fuel injector - my Cyl #1 and #3 injectors were both clogged and would not "tap" - replaced the two clogged injectors, my code P0300 never came back - good luck!

Red89GTA

Intersting issue. My car does the same thing, but it's always cyl 5 (p0305), I've swapped around the plugs, wires, coils and injectors, no change. It always happens around 2k rpm in any gear, usually after cruising for a while in that gear (4th at about 40mph or 6th at about 75mph). Never have felt any misfire either. If this is a similar root cause, I hope one of us figures it out and can share!

jbro90

did eather one of you find out what was going on i have the dreaded p0300 code also it started a couple of days ago all the sudden when i was comeing home from work. started idleing really rough and would stumbble when taking off and ometimes backfire. went and got the codes and came up with p0308 the frist time and one for the driverside front o2 so i changed the o2 and the coil pack cause i ohmed out all the wires and only one was bad at 1100 ohms f#$%!!!!!! so i ordered some new msd wires to get here tomorrw rule out all the wires. i didnt pull the plugs but did run my finger across them and checked for any cracked or broke porcline and notheing i need help this is my dd any thoughts or updates would be awsome also i have ran seafoam through the engine and gas oil is new spark plugs are less then a year old as is the maf and fuel filter and autolite wires the ones i got now

jbro90

oh also guys when i get off on my way performance is good and dosnt seem to missfire

LilJayV10

iTrader: (39)

Why would you not check the plugs?

jbro90

I don't have time to going to pull them tomorrow or tonight

Camaroo1

When mine tossed a Po300 the intake bolts were loose.

xxKennyDxx

Hey guys, sorry ..."been gone" ....


Turns out, just a bad tune. Popped in my original PCM that was tuned (instead of my core), and bam, no check engine light. LoL anybody want some MSD plugs, brand new pretty much.....I thought they were the problem LOL, along with 2 spark plug changes....ay yi yi

All that worrying for nothing, lol.

First cold night of the year here in Florida....man does she LOVE IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!

samckitt

iTrader: (5)

Curious if any resolution has come about on this.

I ask because I have similar issue, but on a totally 03 Silverado with a 6.0L LQ4. And mine only misses when it is first started. I start it in the morning & let it warm up, but even up to operating temperature it misses. If I take off just after starting it, it misses like crazy I basically have to let it idle when moving, any attempted acceleration causes crazy misfires. Even after letting it warm up it misses when driving it, but only for like 3-4 miles from leaving my house, and mainly misses when it is about to change gears. With mine I can feel it & it feels terrible. I have replaced the following within the past 9 months or so, fuel pump, fuel filter, throttle body, intake gaskets, air filter, plugs, wires. Fuel pump was replaced cause it went out, TB replaced because it would intermittenly trigger something & I could not accelerate, & DIC would say "Reduced Engine Power", replaced the intake gaskets to the teal ones cause I thought it might be the problem. No change.

It misses all over the place, not on an individual cylinder. Code says something about the crank sensor. SES light never came on, found out this weekend it didnt because my bulb is bad. Early in the summer I did see it blink like mentioned above.

I don't know what to do, IT IS DRIVING ME F'ING CRAZY. Please advise.

What is this crank relearn thing I read about & would I need to do that if I change the crank sensor?

Once I get a few miles from the house/work, it runs fine.

S8ER95Z

iTrader: (3)

Hopefully this helps someone out there...

I replaced my short block in August but swapped everything over from the original (cam, intake, etc). I started getting the flashing SES light/P0300 code around 3000rpm all day, everyday but no obvious miss. I replaced everything I could think of before finally doing a CASE relearn with HP Tuners. It's been 4 days now TRYING to trip the light/code and it appears to be fixed.

I wasted a lot of time looking for intake leaks, swapping plug wires, plugs, oxygen sensors, etc... A quick 2 minute process appears to have resolved the issue. From the reading I've done it appears there is a calculation that is used to determine if there is a misfire and if anything in that system changes (sensors, crankshaft, etc) it needs updated to properly detect misfires.

http://www.hptuners.com/help/index.h...cmcontrols.htm

robertbartsch

PO300 code is caused by these issues listed below. my guess is bad 02 sensors.... especially since the exhaust has been modified...and had an exhaust leak....


Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

robertbartsch

Since the car crapped out, it is running so poorly that the PCM has decided to stop the car..... I only saw this happen once in my car. this resulted from and coil pack cable not being fully inserted...