P0300 problems
 

Looking at a 06 trailblazer SS and it has a random cylinder missfire. Has a small cam and rocker's were upgraded. Told it has a converter and I know it has a dynomax cat back and a hand held tune. Any ideas? thanks in advance.

stick or auto ?

auto

if it was stick i was gonna tell you possible misshift, causing pushrods to bend, if one or 2 bend enough will still run good but show a misfire code. (sometimes get a small window of hesitation in the upper r's.

1. if wires are original, spray water via a spray bottle on them, n powerbrake it to see if you can feel the misfire.
if wires are bad the water will make mis worse.

2. coils not common to go bad, and if they do would be a dead mis.

3. common with a cam change, if not tuned properly can show a misfire, clear the codes, restart engine and let idle for 5 min. turn key off and repeat process 3 times.
if code is back on the next restart, then clear codes and do the same process except @ 1500 rpms for 4-5 minutes turning key off and doing this 3 more times.

if code is not back. then i would have to say that it is the cam throwing a random misfire code @ idle. (which is known to do, thats why when they are tuned the misfire set light is inactivated/deleted.

Maybe this service bulletin will help?

ID: 10009666
Bulletin #: 3055
Replacement #:

Bulletin Date: 20040101
Date Added: 20041014

Failure Code: 061000 ENGINE AND ENGINE COOLING:ENGINE

Make: CHEVROLET
Model: TAHOE
Year: 2005

Summary:
SERVICE ENGINE SOON LIGHT WITH A P0300 MISFIRE DUE TO MISFIRES MAINLY ON CYLINDER 7. *TT


or this??

http://www.gmfullsize.com/forum/show...ighlight=p0300

cody, do you have a scan tool that you can read the datastream while running?

I have a actron handheld and hp tuners on my laptop.

have you monitored your fuel trims, is the ecu trying to pull fuel @ all (-5 - -20) if its pulling fuel away due to a bad o2 possible misfire code, if maf is dirty can do same but usually trows a maf code.
did you try what i stated above on first reply?

and what cam is in it?

Haven't had a chance to hook up to it yet, waiting for my buddy to buy the truck and get the cam specs.

if it has a small cam and they changed the rocker ratio when they upgraded them the computer will recognize that as a random cylinder misfire. but how small is the cam. and do you know what ratio rocker?