FlamingTA

iTrader: (8)

I was hoping someone could help me with this. While my car was getting a tune it started throwing a random misfire code. I have a dashboss scanner and that is the only code being thrown. I looked at the current misfires and all the cylinders on the drivers side show misfires.

I have done some of the usual troubleshooting things: plugs and wires look good, changed coil packs between sides, swapped front and rear O2's between sides. The only things I have found so far is that if I unplug the MAF the misfires stop, but I'm not sure why the MAF would make only one bank misfire and not the other. It looks like one of the rear O2's is reading pretty low but it is now on bank 2 and the misfires are still on bank 1. I just went on a drive and the misfires stop right at 3K rpms and above. They also stop at about half throttle and greater.

flame

iTrader: (13)

intake gasket leaking? The car will need to be retuned after the repair is made

FlamingTA

iTrader: (8)

If it was an intake gasket why would the misfires only happen on cylinders 1,3,5,7? I

waterbug1999

iTrader: (3)

what car is this on? Rear 02? you have cats on?

BlumaroZ28

Intake gasket is a possibility, i have had leaks close to a certain runner make just that cylinder misfire. When you unplug the maf the pcm goes to a default value for air/fuel ratio that could be why your misfire stop. I would check the injectors on that bank and see what the commanded on time is from the pcm, then compare to the opposite bank. I have also had low fuel psi cause random mifires only on one bank.(the on opposite the feed line usually) hope some of this helps and good luck.

edcmat-l1

iTrader: (10)

When you unplug your MAF you're forcing speed density (PCM defaults to SD). There is no misfire detection in speed density.

You need to determine if the misfires are real. Does it feel like it's missing? If it's one whole bank misfiring, it should be running horribly.

Mike@Diablosport

iTrader: (2)

bent valve?
Weak springs on one side?

jimmyblue

iTrader: (11)

You want to look at the difference between cylinders in
the misfire counts. But misfire detection is kind of an
arbitrary thing and with a cam, light weight converter or
flywheel, etc. you're almost certain to get bugged.

flame

iTrader: (13)

It was just a thought and would take about 2 mins to check with a can of intake cleaner. Without knowing anything about the car and having no data to look at everyone is just guessing.

jimmyblue

iTrader: (11)

An intake gasket leak at a single cylinder will result in
one lean, and closed loop will richen up the whole bank
until the exhaust gas O2 content is average-right and
every one is individually wrong.

If you have this kind of imbalance, positioning the mixture
richer will cut misfiring (despite being not right). Disconnect
the MAF, and you change your airflow basis and likely the
delivered open loop fueling, at least until the trims roll back
around.

FlamingTA

iTrader: (8)

Sorry, I didn't mean to come off badly. It was more of a question since I don't know much about the pcm tuning.

FlamingTA

iTrader: (8)

Ya, sorry, forgot to put in the info about the car.

06 GTO 6-speed stock gears
ERL stock sleeve 421 shortblock (4.03" bore x 4.125" stroke)
Cloyes single roller timing chain
Melling 10296 with lower pressure spring
AFR 230v2 62cc heads untouched upgraded 8019 springs
Manton 11/32 pushrods
Custom cam speced by Patrick G 243/247 112+2 HUC lobes
Tuning was also done by Patrick G
FAST 102 ported by Vengeance Racing
Yella Terra rockers
LS9 injectors
ported stock throttle body
Kooks 1.75 headers, no cats
Corsa Sport catback 2.5"
SLP pully
SNL 4" intake with 100mm MAF
255L fuel pump

The car runs pretty good and doesn't feel like it's misfiring on one bank. When I look at the misfire count per cylinder, the numbers usually go from about 2-9 on the low side to about 50-60 on the high side.

waterbug1999

iTrader: (3)

In your first post its says one of the rear 02's is reading low... if no cats why u running rear 02's?

flame

iTrader: (13)

What are the fuel trims when the misfires are being counted?

stage274

Check the battery, get it tested! This was my problem, even from last year, I tried everything also.
But just turned out to be a bad battery. That is the first thing that needs to be checked before proceeding on chasing this down.

Tyler Griffiths

I have a random multiple misfire. Have done the common fixes. Still no good results. Bank1 02 reading 0 volts causing the short term fuel trim to be maxed out at +25. 02 sensor is new. Reason im intrested on bad battery is that my batter is draining as well.