ricochet

Recently got the Service Engine Soon light at around 4000-5000 RPM. The engine was idling and running rough that day the light came on. Brought it to the dealership and they read P0300 --- Multiple Cylinder Misfire.

Dealership has been on with Nissan tech support. A lot of waiting around for a return phone call. A week past before they did anything resembling the troubleshooting from the service manual (I have a copy). First they thought it was bad gas, so they drained and refilled the fuel. Still has problems.

Then they checked the injectors and coils. They said they didn't notice any problems. Now they've come back to say that they are ordering new injectors and gaskets. It won't be installed until next week.

Any insight on what could be the problem?

The cars performance was definitely hampered with poor acceleration and rough idle and running speeds.

I really hope they've figured it out. The car has been in the shop for over a week. Good thing they hooked me up with a POS rental.

Audito350Z

iTrader: (1)

my money is on the Random Tech cats... when my RT cats imploded I was getting the exact same code and the engine did the exaxct same thing yours is doing....

remove the driver's side cat... that is the one that seems to implode the best... you will clearly see what I mean when you shine a light into the cat from the flow-in end of the cat... the pic shows what mine looked like...

Good luck dealing with RT... they were OK with me, but it took three months to get a new set of cats...

PeteH

ricochet

What would cause that?

And did you notice a significant power drop across the RPM range?

And what prompted you to check the cats?

Audito350Z

iTrader: (1)

Random Tech first attributed the damage to a supercharger or turbocharger setup.... but I don't have either. Next, they said I have a problem with my engine that is making fuel dump onto the cats and ignite. But, the dealership checked everything possible and said that was not true. Besides, if it was true, my OEM cats would also be damaged.

There was a noticible loss in power up to about 4000 rpms. Above 4k, there was a significant power loss... car would bog down and not run worth a crap.

I suspected the cats at the very beginning. The way the car behaved indicated a clogged exhaust system. The dealership checked codes and even asked me to put the OEM plenum on just to make sure. The service tech even drove the car for about 20 minutes while another tech read the Consult computer and they ruled out anything wrong with the engine.

Once I replaced the RT cats with the OEMs the car was running better than ever. I had the dealership check everything again, with the OEM cats and my Crawford plenum, and they said the car is in tip-top condition.

I never dyno'd the car with the RT cats... but my butt-dyno can't feel any difference between RT cats and OEM cats. The biggest difference is the OEM cats are quiter. I still have the OEM cats on the car and I returned the new set of RT cats to Performance Nissan for a refund.

PeteH

PoWeRtRiP

i dont know how the cats could cause a misfire though. likely it is your injectors or coils/plugs. but you said they checked them right? hmm could it be something wrong with your ecu maybe.

Audito350Z

iTrader: (1)

Powertrip... once the RT cats are replaced with the OEM cats, the codes go away. The multiple cylinder misfire code is a result of the other situation that is going on with the car that ricochet did not mention... becuase of the clogged exhaust the car is leaning out so much that the cylinders misfire.

My tech thought the same thing as you and pulled all the plugs and tested each coilpack. Nothing was wrong with any of them, nor was there anything wrong with my ECU.

If ricochet has his tech put the Consult computer on the car and then has someone drive the car, he will see the engine go very, very lean. As the lean conditions present, the computer will do what it can to keep up, which usually ends up with a misfire.

I've had the OEM cats back on my car for three months and have not had one problem. Car runs stong as ever.

Cheers,

PeteH

mode101

your sig has a lot of mods in it. what did nissan say when they opened the hood ? did they have a problem with the mods you have ? did they blame the problem on your mods?

Audito350Z

iTrader: (1)

the dealership I use is Ok with mods.... they did ask me to replace my Crawford plenum with the OEM plenum, thinking the Crawford plenum might have had something to do with the lean condition....

the dealership did not pull the Random Tech cats off the car... I had to go to the shop that installed them for that.... but once the OEM cats were back on the car the dealership was happy to check out the car with the Consult computer, even though I had the Crawford plenum back on the car...

PeteH

ricochet

Audito350Z, did the dealership suspect a clog in the exhaust, or did you suggest bringing it to the shop to swap out the cats?

Audito350Z

iTrader: (1)

I suspected a clogged cat before I took it to the dealership, but I wanted to them to hook it up and pull the codes, just to see what was happening... I did not expect them to spend the time they did trying to diagnose the problem...

when the dealership could not find anything causing the problem, I knew I needed to go to the shop that installed the cats and have that shop swap the OEMs for the Random Tech cats...

the tech at the dealership was surprised to see the damaged cat when I visited the next day...

ricochet

Any damage to the passenger side cat? And how about the O2 sensor?

Audito350Z

iTrader: (1)

the passenger side cat was not imploded like the driver's side, but the internal element was loose inside it's housing... when the cat was removed from the car, I could shake it and hear and feel the internal element moving...

neither O2 sensor was damaged... both are working fine....