Half of engine not firing

[Greg manton]

i am a gm mechanic not (nissan and i am sure it is overfueling that bank try unplugging both o2 sensors and see how it runs, if not your mass air flow sensor. this should switch to base fueling wich most newer comp vehicles have if it runs better you know its in the closed loop ie mass air flow reads air in engine fueled by comp then o2 sensor adjusts due to o2 or no o2. i have seen a/m o2 sensors do this as well if a hot o2 sensor comes in contact with cold water /snow can shock it and will read no o2 and constantly richen mixture only on effected bank. if when disconected taken out of closed loop drive it that way until you can have it fixed

[DY]

Great idea Greg. Thanks.

I'll try unplugging them tomorrow morning.

Some more updates for tonight. I spent all day trying to figure out what the best injector cleaner was. It was a debate between techron, seafoam, BG44. The PEA stuff I can't get readily, so I went out and bought some seafoam to run in the fuel tank. i've used it on bikes with great results.

While there, I had them price out a distributor cap and rotor for me. Wasn't too expensive so I replaced that anyways.

I added a bottle of seafoam to half a tank and drove it around burlington for a bit. lemme tell ya, driving those twisties are seriously underrated in a car.

my butt dyno tells me that the engine pulls a bit harder and is more responsive through all revs. could be placebo. Idling also settles down a bit better if I'm stopped for a bit. When I first stop, it would shake kinda hard, then give it 30-45secs and it quiets down and idles to about 600 RPM.

definitely not as smooth as it could be but it is doing something different.

I'm thinking this is because of the new distributor cap--> better sparks --> less misfire.

I thought about taking the plugs out and cleaning them again but realized that without fixing the issue, they'll just get gummed up again.

Will update tomorrow!

[Red_Liner740]

u kinda hinted towards something

O2 sensors...i'm not sure about the VG33, but on my maxima with the 3.0, each bank has its own separate catalytic and o2 sensor. if the o2 sensor is on its way out its possibly giving u bad readings...not bad enough to cause a code, but bad enough to cause idling issues...

i hate chasing problems like that around...

seeing as its one entire bank giving u the same symptoms you can rule out a few things. in tank fuel pump, distributor cap or coils (depending on the system)

see if the fuel pressure regulators are swappable....swap em between the banks and then run it, pull the spark plugs and see if the symptoms have switched sides. you could have a failing FPR giving u either too much or not enough pressure. that is if its not using common rail fuel feed.

work mech who takes care of our work vans had the similar issue with a friends Ford Escape V6. intermittent misfire, but only on one cylinder....even he couldnt figure it out.

i'm just stumped about the whole pulling out wires and engine not doing anything different...that would indicate those cylinders are not firing, but for 50% of cyl not to fire....believe me you would know...

[DY]

u kinda hinted towards something

O2 sensors...i'm not sure about the VG33, but on my maxima with the 3.0, each bank has its own separate catalytic and o2 sensor. if the o2 sensor is on its way out its possibly giving u bad readings...not bad enough to cause a code, but bad enough to cause idling issues...

The VG30 and 33, I believe, are very similar. the banks on VG33 have their own cat and O2 sensors as well.

if it is a dying sensor, I might just wait it out until it finally throws a code. Any harm in this?

The sensors are $130 each.

i hate chasing problems like that around...

seeing as its one entire bank giving u the same symptoms you can rule out a few things. in tank fuel pump, distributor cap or coils (depending on the system)

only one coil, so that rules that out too.

see if the fuel pressure regulators are swappable....swap em between the banks and then run it, pull the spark plugs and see if the symptoms have switched sides. you could have a failing FPR giving u either too much or not enough pressure. that is if its not using common rail fuel feed.

it uses a one fuel rail for the whole engine with a regulator on the very end of the line. so it can't be that as well.

work mech who takes care of our work vans had the similar issue with a friends Ford Escape V6. intermittent misfire, but only on one cylinder....even he couldnt figure it out.

i'm just stumped about the whole pulling out wires and engine not doing anything different...that would indicate those cylinders are not firing, but for 50% of cyl not to fire....believe me you would know...

That's the only thing i still dont get. I even tried a few times just to make sure I wasn't tripping.

pulling passenger side wires (clean plugs) slowed the engine down.
pulling drive side wires (dirty) barely did anything even though the plugs showed burning.

I'll read up on o2 sensor DIY testing and see what I can do with that.

thanks.

edit:

i went ahead and grabbed the freezeframe from it.

DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 OL_FAULT
LOAD_PCT(%) 28.6
ETC (F) 122
SHRTFT1(%) 0.0
LONGFT1(%) 0.0
SHRTFT2(%) 0.0
LONGFT2(%) 0.0
MAP (IN/HG) 9.2
RPM (/MIN) 1025
VSS (MPH) 0

[Greg manton]

just leaving a problem like this could plug a catalitic convertor (prolly way more expensive). please unplug something and see how it runs. all 0o2 sensors are just high low switches usually 7 volts they just switch back and forth if that helps. this may not be something you can see a problem with but an o2 sensor reading rich will trick the computer (false reading into over fueling ie grounding injectors to pulse them and let the presurized fuel in rail into cylinder) if it reads o2 in exhaust will continue to add fuel.

[frekeyguy]

are you sure its just not something simple like bad plugs or plug wires?

You said new plug wires? what model? what's the resistance?

Have you tried to swap the plugs over? left bank to the right bank? see what its doing then?

and are you sure the distributor is working fine?

[DY]

just leaving a problem like this could plug a catalitic convertor (prolly way more expensive). please unplug something and see how it runs. all 0o2 sensors are just high low switches usually 7 volts they just switch back and forth if that helps. this may not be something you can see a problem with but an o2 sensor reading rich will trick the computer (false reading into over fueling ie grounding injectors to pulse them and let the presurized fuel in rail into cylinder) if it reads o2 in exhaust will continue to add fuel.

Problem's fix!

I unplugged both o2 sensors from the harness. I thought they would be hard to reach but they were right there.

car runs 10x better. exhaust smells a bit rich but thats understandable.

90% of the shake is gone but since its running open loop, I didn't expect it to be perfect.

Thanks everyone for the help!

now, should i replace both sensors or just one? and if just one, how do i tell which one is the bad one?

[Rob]

DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 OL_FAULT
LOAD_PCT(%) 28.6
ETC (F) 122
SHRTFT1(%) 0.0
LONGFT1(%) 0.0
SHRTFT2(%) 0.0
LONGFT2(%) 0.0
MAP (IN/HG) 9.2
RPM (/MIN) 1025
VSS (MPH) 0

Bank 2 is "OL Fault" indicating a problem. It should be closed loop as is the first bank. This may be due to a faulty sensor bad wiring or faulty ECM. I would start with the sensor, they get contaminated after about 80K (depending on driving conditions). Ensure the terminals in the connector are clean and tight with no corrosion present. Add some Stabilant22 to help current transfer in that circuit. It's also odd to see the fuel trims at 0, that's too perfect there should some variance tehere, at least +/- 5%.

[Red_Liner740]

so i got it right?! yaaaaay! what do i win?!

[DY]

Unfortunately, the problem is not fixed. Unplugging both sensors do make the car run like a dream. I plugged them back in after a 5 minute drive just to make sure it wasn't a fluke.

the o2 sensors are definitely doing something bad.

I checked the o2 sensor on the driver side (dirty plugs) and it looks brand new. this is judging from the heat shrink on the connector wires. very clean with no grime on it. The previous owner said he changed out one of the o2 sensors out. I'm just not sure which one.

I checked the passenger side o2 sensor and from the condition, i could tell it hasn't been changed. Partsource had one in stock, so i took the time today to swap out that.

Napa and partsource didn't have the driver side sensor in stock so I didn't get to replace it. At this point, I'm not sure if it is just a bad sensor, or something else is up with it.

"assuming" the sensor was just recently replaced, the wiring or ECM could be the fault.

napa said the part will arrive tomorrow. I'm getting tired of just swapping parts out but it needed a tune up anyways.

driver side sensor is a ***** to get to though. I have a feeling the EGR valve and intake will have to come off. i dunno, maybe the service manual will say something different.

Difference in performance after the o2 sensor swap today? a bit less shake, only slightly better.

if when disconected taken out of closed loop drive it that way until you can have it fixed

just to clarify: i should drive with the o2 sensors disconnected until i fix it? The exhaust was smelling really rich when I unplugged them today.

I'll also check the wiring for the o2 sensor as well and make sure the connector is clean.

so i got it right?! yaaaaay! what do i win?!

interbooze! Thanks!

[Greg manton]

most likely side with fowled plugs be very carefull removing from exhaust they do have a tendancy to pull the threads with them. running open loop will cause poor fuel economy but you can run it like that with no ill effects. it errs on the rich side.

[DY]

most likely side with fowled plugs be very carefull removing from exhaust they do have a tendancy to pull the threads with them. running open loop will cause poor fuel economy but you can run it like that with no ill effects. it errs on the rich side.

Thanks Greg!

I had that happen to me today with the sensor. the thread on the sensor body ripped right off. glad it wasn't the other way around.

any tricks to getting them out safely? I've heard heating them with a propane torch could help. the 22mm special socket is horrible too. tough to get a good grip.

[NP6000]

oxy acetlyne torch is best, if you have propane give it a shot. In my experience the propane doesn't do anything for me.

Chase whatever is left of the threads with either an 02 sensor chaser or a o2 tap.

lots of anti-seize when it goes back in.

[Greg manton]

if you do damage the threads most muffler shops will weld bungs on for about 25.00 each side (bung = special nut that atatches to pipe for o2 sensor to thread into

[DY]

more updates: nothings doing.

Turned out the previous shop did not tighten the sensor down properly. I barely gave it any force and it came loose.

So i took that out and replaced it with the new one. The idle problem did not go away!

I went out for a quick drive and within 5 minutes the CEL came back on.

heres the freeze frame:

DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT(&#37 29
ETC (F) 181
SHRTFT1(%) -2.3
LONGFT1(%) -5.5
SHRTFT2(%) -24.2
LONGFT2(%) -10.2
MAP (IN/HG) 9.8
RPM (/MIN) 813
VSS (MPH) 0

again, bank 2 seems to be acting up. According to Rob, they should be within +/- 5%.

the conclusion that can be made is that: something is wrong with bank 2 when it goes into close loop operation.

since the o2 sensor is guaranteed good, that leaves the wiring harness or the ECM.

maybe dirty plugs from before?

i'm outta ideas here.

[DY]

drive in this morning: doesn't shake quite as hard anymore. I think the ECM has a better grip of whats going on now.

before, I could feel pulsing when I'm slowing down to a stop. it would get bad 1,100 rpm downward.

now, the shaking and pulsing only starts when stopped.

I'll pull the plugs when I get home today and see what they're telling me.

[frekeyguy]

arent you worried about what this doing to your cats? those puppies cost a shiny penny

and in the long term damage to those guys = failed emission tests = no renewal sticker.

[NP6000]

Did you clear all ECM codes and perform a re-learn?

[DY]

arent you worried about what this doing to your cats? those puppies cost a shiny penny

and in the long term damage to those guys = failed emission tests = no renewal sticker.

yes, i'm definitely worried about them. thats why i'm working so fast trying to fix it.

Did you clear all ECM codes and perform a re-learn?

I cleared the code with a OBD II code reader. How would I perform relearn?

Are you refering to idle relearn?

[baked]

Have a compression test and leak down test done!