p0300 pissing me off

[hassoun]

So i've been having this issue since december of last year with my 6.0 01 Denali.
Code is p0300. misfires happen on cylinder 5 mostly but 2 and 4 sometimes. i replaced spark plugs, spark plugs wires, PCV valve, EGR , Coil packs ( just for the ones missing) sea-foamed, checked compression and i still have the annoying code. Truck hesitates and shakes a lot while driving. i ordered one Fuel injector to replace injector#5 and see if it makes any difference. anybody had similar issues ? i hear a leak from somewhere under the engine ( exhaust) so could be my intake manifolds gaskets i dont know.

 

[hassoun]

forgot to mention that i changed the fuel pump and fuel pressure regulator and adjusted pressure to 58 PSI. my injectors are coming on monday. if intake gaskets are leaking would the engine misfire ?

---------- Post added at 06:45 PM ---------- Previous post was at 06:35 PM ----------

just ordered a set of intake gaskets.

 

[Mac]

P0300 is from the Cam and Crankshaft sensor reading a misfire and triggering the 02 sensor due to overheating and abnormal emission.

In short your 02 is reading a higher emission.
(bad CAT, bad Cam or Crankshaft sensor....etc..)

But don't take my word for it. Have it check at the stealership for proper scanning and testing using GM scanners not autozone one.

Sorry DUDE!!!....but you went about this the wrong way by GUESSING TO MUCH and end up wasting your money.....Sigh..

 

[hassoun]

a cam will set a code.i was getting an o2 heater wire code until justin disabled my rear o2's. wouldnt bad cam or crankshaft sensor set codes ? ever a timing chain would also i think. i am suspecting a cat as well.

---------- Post added at 07:10 PM ---------- Previous post was at 07:03 PM ----------

i disconnected the cat yesterday and the truck was still misfiring. so i will eliminate the cat maybe. stealership wont do any good but steal your money and charge you X100 for parts and labor.

 

[BOSS]

Jeff and I were both fooled by a bad cat...I'm going to put a virtual $100 bet that it's your cat clogged.

B

 

[hassoun]

hmm poossible. if its clogged cat shouldnt the truck stop misfiring once i have just the headers connected with no cats ? or maybe no back pressure thats why it still misfires ? i guess i'll replace the parts i ordered and if that doesnt resolve anything i'll get my cats changed. i was looking at magna flow cats. are these too loud ? because i dont want my ride to sound too annoying.

 

[hassoun]

BOSS,
i noticed something new, if i am parked and i press on the gas ( rev it) bank1's exhaust makes a poping noise along with its normal noise. does that mean a CAT ?

 

[amaz]

If the SES light is on, the technician will find a P0300-P0308 DTC with misfires counting on a single cylinder that may or may not be felt. This may occur consistently, or it may occur intermittently. If a tick noise is verified, it will not be eliminated by canceling fuel injectors and the noise will sound like a valve train tick.

It may be the result of any of the following:

1. worn camshaft lobe and/or lifter roller
2. a sticking valve
3. valve leakage
4. a broken valve spring
5. a collapsed AFM (Active Fuel Management) lifter.

 

[BOSS]

hmm poossible. if its clogged cat shouldnt the truck stop misfiring once i have just the headers connected with no cats ?

Jeff's truck was still running lean when we disconnected the cats from the flange and tested...don't ask me why, when he cut them out problem solved

B

 

[BOSS]

If the SES light is on, the technician will find a P0300-P0308 DTC with misfires counting on a single cylinder that may or may not be felt. This may occur consistently, or it may occur intermittently. If a tick noise is verified, it will not be eliminated by canceling fuel injectors and the noise will sound like a valve train tick.

It may be the result of any of the following:

1. worn camshaft lobe and/or lifter roller
2. a sticking valve
3. valve leakage
4. a broken valve spring
5. a collapsed AFM (Active Fuel Management) lifter.

Might be worth taking the covers off and checking the springs, doesn't take long to do from what I learned

B