Still getting random missfires
12-19-2008, 12:05 PM
#1
Still getting random missfires
I was not getting them until one day my gas gauge decided to be weird on me, and I ran it out of gas. Heres the scoop.
I bought the motor complete (was a rolled over 2006 5.3 LM7) and put my cam and all my mods on it and put it in the truck. Then I ran it out of gas and put the motor through more stress that I wanted to. I've run multiple bottles of b12 through it as well as RXP to clean out the injectors. I checked each cylinder with a temp gun and there were a few that were a few degrees colder, but the front passenger cylinder was running at least 50 degrees colder, so I swapped the spark plug with a new ACDelco. I checked it again and it seemed to make it better, but it is still about 20-30 degrees colder last time I checked.
The wires are factory, the spark plugs were ACDelcos from factory (they still looked good and clean despite being out of a rolled motor) and 1 side of the coils is off the new motor, and the other is off my old motor (I grabbed the wrong one when I was putting the motor back together).
My tune has been set up by Justin at Blackbear, so I do no believe this is something that is wrong with the tune. The missfires must not be occuring often enough to set off the check engine light (I'm using a hand held code scanner and seeing pending codes for it) and do not effect driveability except for causing my torque converter to come unlocked on the highway. This is causing me to get crappy mileage so I think I am finally going to try and figure it out.
Heres my plan:
1. Replace all the spark plugs with NGK Iridium TR55 or ACDelco platinums
2. Possibly put new wires on it (I have a lifetime warranty on some borg warner wires)
3. Maybe swap over to the newer set of coils
4. Run more B12 through the tank
5. Replace with 8.1L injectors (I need them anyways, INJ duty cycle hits 105%+ on WOT logging runs
Any other ideas guys? Sorry for the long post, just wanted to give as much info as possible
I bought the motor complete (was a rolled over 2006 5.3 LM7) and put my cam and all my mods on it and put it in the truck. Then I ran it out of gas and put the motor through more stress that I wanted to. I've run multiple bottles of b12 through it as well as RXP to clean out the injectors. I checked each cylinder with a temp gun and there were a few that were a few degrees colder, but the front passenger cylinder was running at least 50 degrees colder, so I swapped the spark plug with a new ACDelco. I checked it again and it seemed to make it better, but it is still about 20-30 degrees colder last time I checked.
The wires are factory, the spark plugs were ACDelcos from factory (they still looked good and clean despite being out of a rolled motor) and 1 side of the coils is off the new motor, and the other is off my old motor (I grabbed the wrong one when I was putting the motor back together).
My tune has been set up by Justin at Blackbear, so I do no believe this is something that is wrong with the tune. The missfires must not be occuring often enough to set off the check engine light (I'm using a hand held code scanner and seeing pending codes for it) and do not effect driveability except for causing my torque converter to come unlocked on the highway. This is causing me to get crappy mileage so I think I am finally going to try and figure it out.
Heres my plan:
1. Replace all the spark plugs with NGK Iridium TR55 or ACDelco platinums
2. Possibly put new wires on it (I have a lifetime warranty on some borg warner wires)
3. Maybe swap over to the newer set of coils
4. Run more B12 through the tank
5. Replace with 8.1L injectors (I need them anyways, INJ duty cycle hits 105%+ on WOT logging runs
Any other ideas guys? Sorry for the long post, just wanted to give as much info as possible
12-19-2008, 12:49 PM
#2
On The Tree
I assume you threw a P0300 code? If you are still running cats, check them, if they start to crap they can actually cause a random misfire before the 02s will throw codes. Check your front 02 sensors for fraid wiring/etc., faulty 02s can also cause a random misfire. Last, check and clean your MAF, a dirty or faulty MAF could be the problem. Also check to make sure all the clamps/connections on your intake are tight.....
12-19-2008, 12:58 PM
#3
I assume you threw a P0300 code? If you are still running cats, check them, if they start to crap they can actually cause a random misfire before the 02s will throw codes. Check your front 02 sensors for fraid wiring/etc., faulty 02s can also cause a random misfire. Last, check and clean your MAF, a dirty or faulty MAF could be the problem. Also check to make sure all the clamps/connections on your intake are tight.....
No cats anymore, and I will take a look at my o2 wires, but they were responding fine when logging. I'll grab some MAF cleaner at work today and check that out.
12-19-2008, 01:42 PM
#4
Staging Lane
Join Date: Sep 2007
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i would guess the sensors the newer trucks if they sense anything wrong with air flow they throw codes like nobodys business mine threw some one time cause fo my rear o2's i had me airfilter lid on loose so i tightened it and it was gravy then had my tuner turn the rear o2 censors off so i could run open pipe WHOOPS............
12-19-2008, 02:46 PM
#5
I also has random misfires when I first start my truck up and let it idle. Is this normal with a cam? I'm running a mild cam 208/212 .554/.558. The truck has been tuned. Maybe these issue's are related...
I think I'm throwing the same code, can't remember.
I think I'm throwing the same code, can't remember.
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