00silver6

iTrader: (4)

p0300- miss fire on all cylinders

Could a bad lifter or a bad spring cause a miss fire? The noise is like a lifter tap. And could something wrong with fuel pressure, vaccum leak cause a miss on all cylinders? I had a p0121-(throtle position sensor) code and after i cleaned the sensor and the passage that it sits in with cleaner that code went away. This happend a little while after installing 30# svo inj., and a racetronix 255, and after the tune i dont exactly remember when ive been fight this problem for a while now and she's my daily driver so any help or ideas please post. if you need more info just let me know

replaced parts- new msd wires, tr6 plugs gapped @35, header gaskets, o2 sensors.

after replacing the o2's felt better response.

after replacing the gaskets the car felt better, and that night the sound even seemed alot quieter even almost gone

00silver6

iTrader: (4)

ttt saflijhroihn

ss.slp.ls1

iTrader: (36)

A P0300 is a random/multiple misfire. It can be caused by anything...bad plug(s), bad wire(s), bad coil(s), faulty injector(s) or wiring, etc.

How do you know it's missing on all cylinders?

eallanboggs

iTrader: (1)

P0300 is random misfires which means the ECM/PCM couldn't narrow down the exact cylinder or cylinders which are misfiring. If it could you would have gotten P0301 or 302 or 30X instead of 300. This tends to point to something common to all cylinders on both banks rather than any specific cylinder. If you have a scan tool you can log a run and monitor you fuel trims(LTFTs and STFTs) to see if you can at least narrow it down to either bank 1 or bank 2. Is P0300 the only DTC that is set?

XpEdItIoUs

iTrader: (44)

PM sent.

00silver6

iTrader: (4)

pm sent X

and like boggs said it cant narrow it down but im gonna check a few more things tonight. and i wish it did give me a number narrowing it down it would be alot easier to find.

00silver6

iTrader: (4)

a good friend did some tuning on her today and the car is running alot better. i think fixing all the things i did before the tune messed up the tune causing wierd things to happen. wierd

waterbug1999

iTrader: (3)

See if you can have your bud monitor your 02 sensors.. Maybe ones lazy and dumping in more fuel then what needs to be.. Also, on my 07 silverado a few weeks back, I had th same code come up and the truck ran like ****.. Turned out it was a broken valve spring.

GM WORLD CLASS

Whooo! Po300 is a fun one. Before you waste too much time, fill up with some premium known good fuel, replace all plugs with a known good replacement, verify that no exhaust restricitons are present, and check your air filter and intake for restriction. If this all checks out ok, then things get complicated. Re-learn crank sensor (depending on vehicle. Some may not be applicable to a crank re-learn). Perform a top engine clean using appropriate j-tools recommended by gm. If you dont got then take it to a dealer for a top engine clean. This will clear up all your injectors, and also get rid of a lot of carbon deposited on your valves and pistons. Its an all around good service to perform. This will fix a random misfire, i garantee it. Its unlikely that all your coils went bad at once. The problem is associated with all cylinders, so start there.

00silver6

iTrader: (4)

thanks everyone but as stated above problem fixed