spawne32

iTrader: (2)

that's not what a leakdown test does lol i dont know what you tested. Did you have the injectors flow balanced or something?

spawne32

iTrader: (2)

double check the coil pack harness on each coil pack assembly, make sure there are no damaged wires.

x1mafia

pulled all injectors from rail. put cleaner in each injector powered them and saw if they had any cleaner come out of them just one injector that was on cylinder 4 that i swapped to cylinder 6 before getting multiple misfire.

x1mafia

i will double check those wires again but the harnesses going to coil packs looked good last time that i checked.

spawne32

iTrader: (2)

that's not gonna check to see if they are clogged or sticky. This is what i mean by a leakdown test, if you have a collapsed lifter, you will need to do more elaborate testing.

x1mafia

ok sorry i was mistaken with that i just saw a you tube video that showed what i did to do a leak down test on the injectors. anyone in the south east Wisconsin northern Illinois border have tools to do a leak down test properly? Otherwise i will have to hit up the store this weekend to buy the stuff to properly do the test. Hate buying tools that ill probably use once since I usually only work on carbed engines. LOL gotta love my old school smokers

rottonj

iTrader: (4)

I would buy 1 new spark plug and 1 new coil and replace if you have not or move around if necessary. Also did you ohm the wires for variances? You have done a lot of diagnosis, if it keeps coming up as cylinder 4 that needs to have a compression test as well. Problems arn't just a GM thing, there is BS with each brand. Keep at it, stay the course and you will get it.

x1mafia

new plugs new wires all the way around swapped 6 and 4 coil misfire didn't move next step is a compression test just been waiting on a buddy bring his tester over. and i know there are problems with all types of cars just was kidding with that.

the shop said that they did a compression test on the car and was fine and that is why i am highly doubting that it would be a lifter as i wouldn't have correct compression on cylinder 4 at that time i wouldn't think. but that is just speaking from prior experience with other vehicles that I used to work on. Just wish I still had all my tools i used to when I worked at GM.

x1mafia

on compression with this engine is it 165 psi on the cylinders? i dont know with this one.

rottonj

iTrader: (4)

You still could have a cracked plug, at least swap that plug with another and see what happens.

x1mafia

one other thing also when i pulled plug on o2 and got the other error the car seemed to be running better. just wanted to put that out there since im tired of smelling rotten eggs. smells like the kids lost one on Easter and i found the next year.

x1mafia

ill swap plugs tomorrow to see if any change on that also. i have a few extra plugs that I can use so I will use another new one.

rottonj

iTrader: (4)

Well I'm sure you know the egg smell is usually cat related , possibly clogged. That could defiantly cause the stumbling issues you are experiencing but not related to the codes I think. Has this car been on any diagnostic scope or just a hand held obd scanner unit?

x1mafia

i took this to a shop that claims they pulled the coil pack off and valve cover off and the lifter was collapsed. My problem with this is after being a mechanic you can tell when someone pulls that off cause you need to have a new gasket and such. They also stated they tested compression but if you test compression on a cylinder that is misfiring and you think its the lifter then you wouldn't have the proper compression on the test. this was a mom and pop shop kinda and that is why i think that this is not related to a collapsed lifter but more something with fuel or air flow. i pulled the mas off and still got same code and like i said before swapped coils new plugs wires.......im beating my head on the 5.3 and still stumped think i gonna get a new cat and run the other tests as suggested before i go for a complete tear down on the engine. funny thing is that they said they pulled the coil pack but when i got back still had the same crusty tape from manufacturer on one of the coil pack bolts so there is no way they pulled or that would have been removed when trying to take off. so i gonna go and get a cat get tools to do leak down compression test and see where that leads. hell at this point might as well pull engine and do a complete rebuild with super charger......lol. then rebuild trans cause that cant handle the engine it has now. But not ready throw in towel yet gonna grab cat and other things anyone suggest anything. Id like to get a more throaty sound out of the car since it has the power but i dont want to add anymore codes to my brain right now.

rottonj

iTrader: (4)

Well I applaud your ambition and willingness to get to the problem, but before you tear this down it should go a GM dealer for diagnosis. Not my usual suggestion but they have many more resources then a mom and pop and for sure have seen similar problems before. Look for the biggest dealer in the area that actually sells some high performance models, that dealership will most likely have some sharp techs.

x1mafia

ya this guy is gm qualified but so am I doesn't say much. I think that i will have to try that but in mean time i think that i will replace that cat. check plug. maybe ill just leave the other test to the dealer to see what they find. I dont know what a diag will cost but hopefully they will be able to see what the prob is quicker than I can. I contacted gm and already talked to someone gm dealers want 3k plus to do the job so this is definitely going to be a hit for sure I hate having to have my car serviced by anyone as most of it i can do in my garage or on my lift.

rottonj

iTrader: (4)

Good luck. Post back your findings.

spawne32

iTrader: (2)

If they told you its a collapsed lifter, pull the VC off and take a look. The valve cover gaskets are reusable. Ive had my valve covers off numerous times, only if the gasket is bad can you not reuse it. The DOD lifters are notorious for failure so I wouldnt be surprised.

superglide9375

i had this code and put new maf and map sensors in went away.when it didnt move when u swithch coils has me thinking electrical or electronic such as feedback from a sensor

Pauls325

iTrader: (1)

i would like to know the exact codes that are being thrown. the ecu uses the knock and crank sensor to detect individual misfire events. p0300 codes are thrown when the engine detects misfire events that occur enough to cause emissions problems.

the misfires over time can be bad enough to cause your cat to overheat and cause damage.

Also you should note with these codes the ecu will actually shut off that fuel injector to protect the cat.

keep in mind this code could be set by vibrations that are not misfire related.... for example if it is being set by exhaust system vibration then the ecu thinks "misfire cyl 4" and disables that injector causing rough running.

look for unbalanced tires, drive shafts, brake rotors that are different thicknesses, damaged accessory belt or components, damaged reluctor wheel, also the crankshaft variation learn procedure may need to be performed.