P0300 random miss fire slightly modified 4.8L
01-27-2011, 02:00 AM
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P0300 random miss fire slightly modified 4.8L I have code PO300 random miss fire. I have a 4.8L with LS2 intake, 06 SSR throttle body, and long tube headers high flow cats, cold air intake, SSR mass air flow sensor LS2 knock sensors, LS1 flywheel and Zo6 clutch disk, LUK pressure plate. 06 SSR manual transmission tune, and 06 SSR E40 PCM. I also am getting P0172 and P0175 rich codes it runs like crap black soot and lots of water out the exhaust. It seems to really stumble when letting out the clutch starting and stopping, it is constantly missing so bad that the check engine light is flashing? Is this mechanical or a tune issue where to start?
Does the coil pack need ground to the valve cover at all? I have very high resistance to ground on my valve covers, I am assuming this is normal, as there is a gasket between there, I have never seen a ground strap from the valve cover to engine block??
Also my engine mount is contacting the frame will this set a false miss fire?
Does it matter which way the LS2 knock senor connector points ie; up down front back etc..?
Does the coil pack need ground to the valve cover at all? I have very high resistance to ground on my valve covers, I am assuming this is normal, as there is a gasket between there, I have never seen a ground strap from the valve cover to engine block??
Also my engine mount is contacting the frame will this set a false miss fire?
Does it matter which way the LS2 knock senor connector points ie; up down front back etc..?
02-04-2011, 07:44 AM
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grounding question I also have an issue with the block ground and valve cover grounded. I see I am pulling ground from the valve covers right thru the coil pack bolts. I am not sure if the valve covers need to be grounded or separated from ground due to the fact that the ls1 center valve cover bolts have the rubber bushings in them and a gasket thick enough the cover never touches the block except from the bolts that have the rubber grommets on them. Looks at first glance designed to separate the ground to the valve covers due to the coil packs sitting on them
Logically you would think the design would dictate no ground to the valve covers but after adjusting the valve covers I could not attain less than .02v. Tightening the valve covers definitely allows me to pull the full 12 v thru the valve cover but since the coils work off grounds to the pcm I was wondering if this valve cover grounding has any affect on the coil ignition system.
Sorry I only have more questions for this similar issue
Logically you would think the design would dictate no ground to the valve covers but after adjusting the valve covers I could not attain less than .02v. Tightening the valve covers definitely allows me to pull the full 12 v thru the valve cover but since the coils work off grounds to the pcm I was wondering if this valve cover grounding has any affect on the coil ignition system.
Sorry I only have more questions for this similar issue
02-04-2011, 07:54 AM
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most cars i get with random missfire code and bank 1 and bank2 being rich are caused by either dirty maf, fouled o2, bad tune, and sometimes it just goes away.
but as you said you get black smoke then you are indeed really rich, did this just happen? or after you got it tuned?
but as you said you get black smoke then you are indeed really rich, did this just happen? or after you got it tuned?
