2005 Maxima has 193K on the clock. Has had a P0420 code for a bit, but just started running rough. (Clarification: Idling rough and SES light blinking at times when more throttle given. Wife reported it would bog down when trying to accelerate. I babied it to get the codes pulled and the light still popped and ran rough) Pulled the codes and got the following:
P0305 Cylinder 5 Misfire

Secondary Codes
P1148: Closed Loop B1
P1031: A/F Sensor 1 Heater Bank 1
P0420: 1 catalyst. 2 catalyst system Bank 1
P1276: 1. A/F Sensor 1 Bank 1. 2. Cylinder 1 Cylinder 4 injector.

Looking at it I'm guessing there are multiple problems. Don't want to put a bunch of money in it and this mileage but looking for suggestions on how to diagnose from here. Thank you in advance.

 

Researching some and looks like the P0305 could be plug or coil for cylinder 5. Diagram I found shows it under the manifold. I'm guessing it'd be best to replace all three coils under manifold, all 6 plugs, and the manifold gasket while doing so. Thoughts?

 

Cross your fingers the catalytic converters are not damaged.

Replace as many coils as you can. In my experience when one goes, others are sure to follow.

Spark plugs now would be a smart idea.

Check for leaking valve covers and cracked rubber hoses for the PCV system.

 

Busted up cat substrate clogging the exhaust. ...Among other things.

 

Well, replaced all spark plugs, back three ignition coils and the PCV valve….ran it up and down the street just fine. Wife went to the grocery store and it’s doing the same thing. I’m guessing cats are next. This car has about 6 months before wife wants to buy a SUV…what are the options? Gut the cat? Any cheap options on cat replacement?

 

Gut them.

 

ok so decided to try the Scotty Kilmer method and try putting laquer thinner in the tank….ran it a while and now I have the following codes
1148
1031
0301

Odd it’s now saying misfire in cylinder 1, when i just replaced sparkplug and ignition coil

 

Gasoline goes in the gas tank. Nothing else.

 

Thanks you're a peach. Kinda past that point aren't I. Interesting, however, my P0420 is gone. Not saying it won't be back.

 

Well since this forum is mostly dead I'll just document the process. My plan is to replace the bank 1 O2 sensor which will hopefully remove the 1148 and 1031. The back ignition coils are all new so I'll likely swap the 1 & 3 coils and see if my code moves. If it does I'll replace that coil. Will see where things go but the next step would be to gut the bank 1 precat.....which I may do while I'm in there.

 

Correct, this forum has died significantly in the last couple years, Gen6 has always (since I signed up) been a ghost town. Check out JSutter's Join Date. He's been here a while. His post summed up your work flow. I expanded on it a bit with my post, but beyond that, not much left for the rest of us to answer. I think you're on the right track. Keep us updated.

 

My Suggestion to you in to Stop Firing the parts cannon at this and Diagnose it. Use The scan tool or what ever device your getting codes from.. Use its live data Function, and look at the Values.

Typical cat failure on any Vq, never results in the car running again by a tune up, They stop up and all the engine can do is idle. Under any load the engine just dies.. A truly Horrible Sound, they almost sound as if the timing has jumped. Which is only fixable by replacing them. My suggestion to you is if your wife drives this car, Don't Gut them. This engine stinks to holy hell catless. An ebay set all three pieces is under 300 these days. I've installed Several actually with not an issue I can report.. Do a few highway pulls if you think the cats are shot, get them really hot, and keep your phone close. In the Shop if I suspect a Vehicle to have a restrictive Cat, I do a Back pressure Test. The a/fs get replaced with gauges and off we go to test. May be worth having this done at the hr labor rate most shops charge. You can replace them your self if the Values are too high. However replacing them on a whim is a Horrible thing to undertake if that is not really your problem. Tech Tip: Rear Cat top bolts are best removed with the Upper Intake Removed and Long extension.

From what I read Your problems seem elsewhere.

 

Wasn't trying to "fire the parts canon", but thought it prudent to replace the spark plugs as they were original, and the back three ignition coils while the intake was off. Now that I've taken the intake off twice and realize how easy it is, I don't think replacing all three back ignition coils was necessary. I do appreciate the input from all.

Anyway, on with the show. I removed the intake manifold again last night. I swapped the 1 & 2 ignition coil. That was kind of preventative if the P0301 code related to the new coil....doubtful, but at least if the code moves it'll be easier to replace. I did zero out the codes last night, which I hadn't done between my code posts. I didn't take it for a drive, but did start and rev it in the driveway. Light blinked and 1148 was the only code. I have decided to replace the air fuel sensor (upstream bank 1 O2), but have to get an O2 socket to remove that bastard. Climbed under the car and did notice the downstream bank 1 O2 was slightly melted at the connection. I'm not sure if it's enough to cause a problem or just the plug plastic melted a bit. Also not sure if this is from running the car hot on lacquer or was already this way. But it's my understanding the downstream O2s really don't affect car function...correct me if I'm wrong.

Cardinals WC play-in game tonight, so won't get any work done till later this week.

 

Replaced the bank 1 sensor 1 oxygen sensor and that did the trick, no more SES light and running like a champ. thanks to those who responded in this thread

 

P0420 came back yesterday. Car runs great, no power loss. Wondering if the melted plugs on the downstream O2 is causing the sensor to not operate correctly and so it thinks it has the precat clogged?? I'm gonna fix that wiring and see what happens.

 

This car has about 6 months before wife wants to buy a SUV…what Showbox jiofi.local.html tplinklogin are the options? Gut the cat? Any cheap options on cat replacement?