NissanSkylineN1's 2004 G35 Sport Coupe Automatic -Sputter Fixed!

[NissanSkylineN1]

Hi all,
Its been a while since I've posted here - But I need your guys help. This issue drives me crazy.

My G35 Coupe has this rough idle going on since March, where the exhaust sounds like its sputtering. If I give it gas in park, it will also do this sputtering as well. However, when I am driving it, it is not noticeable. The exhaust smells a little rich, and it is throwing a pending P0306 (6th cylinder Misfire) code. The issue disappeared for a day when I did the oil change, and also goes away if I take it for a spirited drive.
I have replaced:
- EVAP Canister Purge Valve
- Rocker covers on both sides
- Ignition Coil
- Spark Plug
- PCV Valve

I have also ensured all vacuum hoses are on properly and that there are no intake issues. I cleaned the throttle body and did an idle relearn as well.
I have attached a diagnostic report from an OBD software to this post. Below are the videos I took, one from the engine bay (by Cyl 6) and one from underneath the car, under the rear muffler:


Any ideas on what the issue might be?

 

[SVX]

How is your recent fuel economy? Is it any different lately? I've had similar idling issues with my Corolla as well. What did the old spark plug look like? Was it white from running lean? The last couple of things I've left to do to my car after replacing the coil packs and oxygen sensor, is to replace to fuel filter and clean the injectors.

 

[NissanSkylineN1]

How is your recent fuel economy? Is it any different lately? I've had similar idling issues with my Corolla as well. What did the old spark plug look like? Was it white from running lean? The last couple of things I've left to do to my car after replacing the coil packs and oxygen sensor, is to replace to fuel filter and clean the injectors.

SVX! You’re still around!

Fuel economy hasn’t changed much - if anything, its improved since I’ve switched to Costco gas.

The plug electrode had a mix of a crusty white and brown (these cars burn oil a little) which I scraped off. The screws threads on the plugs had some black spot on them. However, they’re not due for a change, as I put in Iridiums only 50,000km ago.

I’m also thinking it might be a bad injector - it’s a pain to remove on the VQ because you gotta remove the plenum.

 

[eiriksmil]

Cleaned the MAF?

 

[Tappajakoala]

I had couple days ago P0300 OBD code with my Sebring. Description said there's been counted too many random misfires in any cylinder so it sent computer a warning. I've had 3rd party flexfuel system for it several months and I know it wakes up more worse with ethanol than with petrol. My conclusion was the cold star leads to misfires, so I safely erased the code with my obd scanner. Problem solved.

EDIT: In my case check engine warning took precautions and set computer into safety mode and didn't allow revs go above 4000. On going warning might even cause bad idle?

In your case it's still plausible its injector fault or spark plug fault.
https://www.obd-codes.com/p0300

 

[NissanSkylineN1]

Cleaned the MAF?

So I went out and bought a MAF cleaner today. It was quite an adventure.
The MAF on these cars is in place with 2 Security Torx screws. That took me an hour to get out.

Anyways, cleaned the MAF, and I'm still having issues 🤬🤬🤬

I had couple days ago P0300 OBD code with my Sebring. Description said there's been counted too many random misfires in any cylinder so it sent computer a warning. I've had 3rd party flexfuel system for it several months and I know it wakes up more worse with ethanol than with petrol. My conclusion was the cold star leads to misfires, so I safely erased the code with my obd scanner. Problem solved.

EDIT: In my case check engine warning took precautions and set computer into safety mode and didn't allow revs go above 4000. On going warning might even cause bad idle?

In your case it's still plausible its injector fault or spark plug fault.
https://www.obd-codes.com/p0300

I noticed that at steady RPMs, there is no misfire. However, as soon as the RPMs climb or drop, the misfire occurs. I'm starting to more think that its the injectors...

 

[KinLM]

So I went out and bought a MAF cleaner today. It was quite an adventure.
The MAF on these cars is in place with 2 Security Torx screws. That took me an hour to get out.

Anyways, cleaned the MAF, and I'm still having issues 🤬🤬🤬



I noticed that at steady RPMs, there is no misfire. However, as soon as the RPMs climb or drop, the misfire occurs. I'm starting to more think that its the injectors...

Is it manual or automatic? I know that on my Mustang, after changing the clutch, the car needed a crank position “reset”; any kind of acceleration/sustained RPM above 3,000 RPM would cause it to misfire.

Its more likely to be something pertaining to cylinder 6, but it’s just a thought.

 

[NissanSkylineN1]

So since my last post I've done a few things:

1) I bought a new intake! My hoses were ripped and I figured a new OEM hose would be more expensive than a cheap eBay intake. So I spent $50 and bought a brand new cold air intake to put into the car. I ended up keeping the stock airbox and only using the tube and filter from the intake to keep it as OEM as possible. Didn't solve the misfire.

2) I greased both of my front brakes as they were squeaking really loud! My silly brother had used thick copper grease instead of brake grease! Now they're whisper quiet.

3) My transmission cooling line was all rotten and rusted out! I noticed it was leaking around 25ml of fluid every night and leaving spots all over the driveway! The other day I felt like the tranny was slipping so I went to the mechanic and had that replaced for $650 all-in right away. Didn't solve the misfire.

4) My undertray was all ripped up. A new undertray came in today from RockAuto. Now I gotta go to the Home Depot to get some new bolts for it!

While I was at the mechanic, they mentioned that my resonator has a crack in it and that it needs to be replaced. They quoted $300 - I'm hoping that this is the cause of the misfire... I'm getting pretty tired of fixing this car now!

Is it manual or automatic? I know that on my Mustang, after changing the clutch, the car needed a crank position “reset”; any kind of acceleration/sustained RPM above 3,000 RPM would cause it to misfire.

Its more likely to be something pertaining to cylinder 6, but it’s just a thought.

Its an automatic.

 

[NissanSkylineN1]

Misfire fixed! Took it to a mechanic and apparently 4 of 6 spark plugs were loose, and the "pre-gapped" plugs weren't so gapped after all!

 

[SVX]

You did all of that work to not check the spark plugs properly?

 

[NissanSkylineN1]

You did all of that work to not check the spark plugs properly?

So I decided to check my plugs yesterday and change them. Here's how they looked :