BlackCloud83

ok , this is my first post here...i have a 2002 chevy 2500hd with a 6.0l true dual flowmaster 40's k&N in the stock box ( with a pvc intake tube )

heres my symptoms:
-rough idle
-p0300 code only ( comes up above 2400rpms only )
-poor fuel mileage
-shakes prettybad on highway ( hops around town ) and the driveline is all mint and tires are balanced properly
-i really have to get on the throttle to go any where
-exhaust note is nice and snappy when the engine is cold but once it warms up it starts " poping" and sounding like $hit ( noe leaks either )

What ive done ( using 3 of my gm certified buddys ideas and my own )
*new plugs/ wire per gm spec
*coils tested and all are good
*new fuel pressure regulator
*8 new balanced injectors ( mine were junk )
*new fuel pump ( mine was failing )
*new updated green intake gasket
*fuel filter
*cant find any craked vacuum lines either
* checked for broken valve springs and none present
*compression is 175 lbs on all 8 cylinders
*2 new rear O2 sensors that were bad
*fixed broken power wire on EGR
re set pcm too


heres my thought, i think i have a pluged or melted cat ! bank 1 cat gets hotter twice as fast as bank 2 does my LTFT2 is higher all the time by 1-2% than LTFT1
O2 readings (taken when engine was driven for 1hr and at idle )
B1S1 -.2-.88
B1S2- .2-.288 ( this sensor is new )
this cat was running alot hotter
B2S1- .2-.80
B2S2- .1-.6

BlackCloud83

oh, and i forgot to metion i can only get it to rev out to 4500rpms..fuel pressure is 53lbs ( static ) 51lbs idle and gos to 62 when i raise to 2k rpms seems more and more like my malfunctioning egr ( since fixed ) was causing a misfire that destroyed my cats and i still have themiss

kmracer

iTrader: (1)

get a cheap vacuum gauge and hook it up. if vacuum drops at 2k rpm's, the cats are clogged.

also check your MAF and MAP sensors. make sure no air is leaking in downstream of the MAF. idk if you have access to a good code reader, but thats really the only easy way to check out the MAP.

BlackCloud83

my map reads 10.9 at hot idle and when i bring the throttle up to 2k it drops down to 6hg or so , my maf is clean too and it reads .79 at idle

kmracer

iTrader: (1)

what mods?

and hoestly, if its not an HCI car, i have no idea what it should be. hahaha. maybe google some specs. does that MAP reading go down at 2k rpms? hold it for 10-20 secods or so. MAP=compooterized vacuum gauge.

BlackCloud83

haha ya iknow its a truck thing but the engines are pretty much the same too, plus im running ls2 heads from a 04 gto and a stock zo6 cam but yes the MAP reading drops and stays down when the rpms are raised to 2k

my buddys 5.3l MAP reading gos up when throttle is opened up so i think its time for some magnaflow cats

which cat is more likely to be bad the one that gets the hottest i assume cause the internals would melt from a rich condition

kmracer

iTrader: (1)

if one went, the other probably isnt far off. replace em both! haha. but good. glad you got it worked out.

BlackCloud83

ya, i was planning on it..im short on cash right now but im going to punch them out in the am just for a few days till i get paid so my truck can actually be driven without getting 6mpg

BlackCloud83

anyone else have some imput before i cut my exhaust to pieces