AR15 guy

iTrader: (1)

First off 2 weeks ago I did a long tube install and removed the rear o2's. I have not tuned it yet, but it has ran fine until today. Of course it was always throwing the rear o2 sensor not detected codes.

Today it started missing very very badly. I took it to work and stuck it on a snap on scanner. I am getting misfires on the passenger side cylinders only. #6 getting the misfire's the worst, #4 behind it and 2/8 rarely getting any.

When I first scanned it cylinder 2 had 336 misfires, #4 had 20, #6 had 2551, and 8 had 41. After clearing them #6 is still missing the most, but #4 isn't that far behind.

I also threw code p1153 which is the bank 2 sensor 1 o2 sensor. aka insufficient switching. That is the side the misfires are on as well.

To make things even more odd, it will run for a minute or two upon restart fine with no misfires. But then it will start missing badly. Could the o2 sensor affect 1 bank only?

twitchtwice

iTrader: (12)

make sure your coil pack was installed correctly. if everything there is fine i would move to the wires. make sure the wires are all on the coil pack and plugs properly. if thats not the case you maybe out of some fluke cracked all the plugs on that side?

try that and report back.

AR15 guy

iTrader: (1)

I have not disconnected the coils in any shape or form since buying the car. The wires are secure, and I pulled the #6 plug and it looks fine, it is starting to foul just a wee bit. I swapped wires with the other side and they didn't change anything. The plugs are tr55's and they are ~10k miles old and the wires are MSD that are also a year old.

I have kind of ruled the plugs/wires out because it runs fine for at least 60 seconds after being started each and everytime. Then starts to miss. I even watched the scanner while it was running and it has zero misfires at first.

RRhodes1

maybe your header gaskets had a split in them ?

thats where i'd look after checking that the plugs arent cracked and all the wires are plugged in the way they should be

AR15 guy

iTrader: (1)

Ok...I swapped wires around and it did nothing. New coil also did nothing.

Now I am only getting misfires on #6 more or less. I will get 700+ and a couple other cylinder may only have 5 or something. I am going to try a plug I guess and see what happens.

BTW...zero misfires from any cylinder for the first 60 seconds or so. Then it gets progressively worse.

1quickirocz

im going to say you may have a bad B2 S1 o2 or wiring to it. It seems like by the way you describe it that its running fine in open loop (PCM not reading o2s) then when it goes to closed loop( PCM makes fuel mix decisions based on o2 readings) maybe the bad sen or wiring is throwing off the PCM causing either a lean or rich condition that causes a misfire. just something to check.

AR15 guy

iTrader: (1)

I believe that o2 is dead. Its reading 1107mv all the time while the other side is cycling fine. Maybe the plug is bad on #6 and it is just exaggerating the problem when it starts to run rich. Soon as it goes into closed loop it starts to run badly.

1quickirocz

check the wires to the o2 sen and make sure they are not burned up on te header. happens alot. if its fine then repl the sen.

35th camaro

have seen this at work many times, bad 02 sensor

AR15 guy

iTrader: (1)

It was in fact the o2 sensor. The only reason I was stumped is because #6 was missing so much worse than the rest. I thought for sure the coil or something was bad on that cylinder.

1quickirocz

Bad o2s will cause all kinds of stupid probs that make no sence.....glad you got it fixed.

bobby austin

need help did a used engine swap on mu 2001 firebird ls1 and now wont fire on #2,4,6,8 it has a p0300 p0302 ,p0304 p0306 p0308 will not fire coils but do have injector pulse?

Mart00SS

iTrader: (19)

Main coil connector for bank 2 plugged in?

rich911s

Just went through the same p0300 multiple misfire problem on 2003 GMC Yukon with 5.3. All the misfires were on the passenger side mostly on #4 and #6. Symptoms were no power over 2,500 rpm, a flashing check engine light, and p0300. Changed out the o2 sensors ($36), plugs ($25), wires ($28), and fuel pressure regulator ($16) with no improvement other than a much smoother idle. Cut out the passenger side cat as a last resort before taking to the mechanic and a pile of dust came out as it fell to the ground. Started up the truck and the problem was gone. If you're having similar symptoms this may be your issue. Bezos and friends sells a cheap exhaust back pressure tester for about $35 which could've saved me some welding if I was wrong, but as it turned out I guessed right. In addition, I wasn't necessarily throwing any parts at the problem as this 330,000 mile truck was way overdue for a serious tune up. Runs like a top now. Hope this helps someone!