random cylinder missfire? WTF?
02-09-2009, 09:08 PM
#1
Staging Lane
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random cylinder missfire? WTF? ok, so last week im driving home and my car starts to run really rough with no power. I scan it and the code says random cylinder missfire, well the month before i replaced the plugs but not the wires so i figured it was that. I replaced them and didn't have a problem. Today I wake up and go to work and it started doing it again for bout 1-2 minutes! and then went away and drove like normal!? I went into work and then came out bout an hour later to go to the bank and same thing happened again! only ran rough and "missfired" for bout 1-2min and then ran normal. On my way home today i stopped by Autozone and had him check the codes and it said the same thing. He asked if I had any mods done and I told him no cats, headers, intake, removed my EGR and air hose, but I have not had it tuned yet. He suggested that I get it tuned. Im thinking it might be something more than that cause I have had the headers on for over a year. I was thinking maybe Crank position sensor? Anyone have any ideas? 
02-09-2009, 11:01 PM
#3
Sounds like you may have a bad connection on the crank sensor or a loose ground. There have been a few instances where I've seen the pins in the crank sensor plug go bad. I would check the grounds on the back of both cylinder heads and inspect the CPS connector for signs of a poor connection(corrosion or discoloration).
02-09-2009, 11:31 PM
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Pull the plugs and check them closely under a bright light for hairline cracks. You may have slightly cracked one during the install. I had the same problem with my LS6 and it was cracked plugs.
02-10-2009, 10:16 PM
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Staging Lane
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I have not had a chance to check anything cause I have been so busy, but I will on Thursday. I just don't understand why it comes and goes? I figured it would stay constant or something?
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02-10-2009, 10:27 PM
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Check your front O2s. Did it specify a bank? I drove through a deep puddle and burned up one of mine and it did that on off misfire stuff until I replaced it.
02-10-2009, 10:29 PM
#9
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I have a M6, Ill have to check the codes again becuase I did remember seeing somthing bout O2 sensor codes but I kinda ignored it cause I don't have any cats and I figured that was what they were talking about.
Was it both of your front o2 sensors? and was the wire like burned up? how could you tell it needed to be replaced?
Was it both of your front o2 sensors? and was the wire like burned up? how could you tell it needed to be replaced?
02-11-2009, 12:48 PM
#10
are you using ngk TR series plugs?
my car would miss and sputter until the engine was at operating temps.
change to a non projected or an autolite of the same heatrange.
when i switched to autolites, my problem dissapeared.
it might not be the plugs, but its the cheapest part, so look there 1st.
my car would miss and sputter until the engine was at operating temps.
change to a non projected or an autolite of the same heatrange.
when i switched to autolites, my problem dissapeared.
it might not be the plugs, but its the cheapest part, so look there 1st.
02-11-2009, 02:06 PM
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It could very well be one of your front 02 Senors. Mine did the same thing and it threw 3 codes. The random misfire and 2 relating to the 02 sensor. Scan it again, write down the codes and check on LS1Tech for the definition if the scanner doesn't already tell you what it is.
It shouldn't be a rear 02 sensor since they just check to see if the cats are working, and well you have no cats. Did you run 02 extenders when you installed the headers? The code will say something like B2-S1 or B1-S1 which means Bank2-Sensor1 or Bank1-Sensor1. Just remember:
Bank 1: Drivers side
Bank 2: Passenger side
Sensor 1 = Before the cat.
I replaced sensor 1 on bank 2 and had to unbolt my y-pipe, unbolt the cat from the manifold and drop it out. Let it cool down, spray it with penetrating oil and it should twist right off. Remember to hook the scanner back up after you install it and clear all codes. Did this a week ago and nothing has popped up since. Hope this helps? - Zack
It shouldn't be a rear 02 sensor since they just check to see if the cats are working, and well you have no cats. Did you run 02 extenders when you installed the headers? The code will say something like B2-S1 or B1-S1 which means Bank2-Sensor1 or Bank1-Sensor1. Just remember:
Bank 1: Drivers side
Bank 2: Passenger side
Sensor 1 = Before the cat.
I replaced sensor 1 on bank 2 and had to unbolt my y-pipe, unbolt the cat from the manifold and drop it out. Let it cool down, spray it with penetrating oil and it should twist right off. Remember to hook the scanner back up after you install it and clear all codes. Did this a week ago and nothing has popped up since. Hope this helps? - Zack
02-11-2009, 07:25 PM
#13
also check vac leaks i had one at the pcv the hose going into the intake but we also did some different tuneing on her so, and I was also throwing a tps code turned out the tps was turning free and didnt spring back so check that also because it was throwing it all at the same time. I havent had the code since. good luck that p0300 is a bitch
