Yet another RB Neo misfiring thread after reading all the others.

[uchoa]

1. Hey folks. I've been lurking and browsing the forum for a while, since I got into my head that I wanted a skyline.

Having purchased an overpriced completely stock GTT, (only "mods" it has is HKS pod filter and catback) now that it became legal in the US, it was all glorious and sututu noises here and there. But then I wanted to do things right and went to do basic maintenance.

After all the fluids, filters done, I did the spark plugs, that's when the problems started..
First the car started spluttering at around 4.5k RPM. Which I gapped down the new plugs and that solved the sputter there, but the car now always misfires at idle with pops when lifting off and shifting 2nd to 3rd. Similar to the issues in this recent thread.

I've been banging my head against the wall, reading the threads here and trying suggestions for a couple months now, so decided to start this one to explain exactly what I tried and what is going on.

The symptoms of the issue:

• Idle and low revs misfiring intermittently. You can hear the exhaust tone change and the shakes on the shifter knob. It happens frequently, but doesn't seem to have a rhythm to it.
• Pops when backing off throttle. It pops and or burbles almost feels like it spits fire when it pops. (Happens mostly in 3rd gear at around 2k RPM).
• When under load and after 6k RPM, it also pops when shifting from 2nd to 3rd.
• There's a ticking noise at around 2k RPM in 2nd gear going downhill, seems unrelated though but I am out of educated and downright dumb guesses.
• Not noticeable lack of power when putting the car into load.

The attempted diagnosis and solutions:

1. Unplugging coils when the car is running
   • This did nothing to change the idling and tone shift for every cylinder.
2. Checking the exhaust headers with thermometer
   • They all are within what I'd say it is margin of error of the laser thermometer
3. New spark plugs
   • Tossed two new sets, copper, iridium and using the old ones, still misfiring, even re gapped to 0.8mm, still same thing.
4. MAF cleaned with the "specific" spray cleaner
   • No changes in the issues what so ever.
5. Brand new loom and r35 coil conversion (was going to add the r35 coils anyway)
   • car runs arguably better, still misfires, but seems like does less frequently. Placebo?
   • Code 21 now being thrown, thanks nissan gods.
6. Removed the CAS to check the shaft for play or anything.
   • CAS seems all fine, nothing that indicates any issue, visually speaking.

Things to attempted next:

1. Ordered a new MAF (chinesium from Amazon, to be able to return regardless of result).
2. Fuel with proper gas, maybe it is this California water that they sell as gas that is to blame?
3. Plugin the link ECU and check the info using the built in base map.
4. Go back to BMW and eat my rob bearing breakfast without milky oil mixture.

 

Do any of you have experienced anything like this or have any suggestion?

[GTSBoy]

15 minutes ago, uchoa said:

Ordered a new MAF (chinesium from Amazon, to be able to return regardless of result).

Don't try it. It will be shit. Better chance of damaging the engine than gaining any knowledge about the old one.

17 minutes ago, uchoa said:

Fuel with proper gas, maybe it is this California water that they sell as gas that is to blame?

Maybe, but unlikely, especially if the O2 sensor is working.

17 minutes ago, uchoa said:

Plugin the link ECU and check the info using the built in base map.

You can use NissDataScan to look at the stock ECU.

 

Cleaning the AFM is seldom necessary and seldom helps.

The R35 coil & loom conversion should eliminate dud coils or plugs. But as you still have misses - look to the plug where the coil loom connects to the engine loom, and the CAS plug. Need quality connections there. Also look to injector plugs. And the AFM plug while you're at it. Also look to whether your injectors are clean and flowing evenly. Get them out and onto a testbench.

[uchoa]

2 minutes ago, GTSBoy said:

look to the plug where the coil loom connects to the engine loom, and the CAS plug. Need quality connections there. Also look to injector plugs. And the AFM plug while you're at it. Also look to whether your injectors are clean and flowing evenly. Get them out and onto a testbench.

Good tips, will get on those tomorrow. When doing the maintenance I did move a few of those connectors around, and things that are old tend to not like moving around. (Like me).

[uchoa]

Alright, all the plugs looks good.
Noticed that it starts to get bad when the car is up to temp, that's when things starts to misfire hard.
next to do is Injector cleaning and such. Got in touch with a shop to do work on the injectors next Monday also help on diagnosis.

[GTSBoy]

Misfires when the car is fully warm are generally attributed to the coils (and/or the igniter, on cars with a separate igniter). They can stop working properly when they get hot for a number of reasons. Either electric/electronic, or from thermal expansion opening up gaps and allowing HV leakage.

Seeing as you have replaced the coils, that could/should rule them out. But I wouldn't always assume so. Were the coils genuine? Or is there a chance you have bought some counterfeit Chinesium shit?

Then we're back onto loom connections. They can fail when warm/hot for the same reasons. Inspections, cleaning of contact surfaces, ensuring that terminals are fully inserted, etc etc, are all justified.

The same (heat effects) holds true for the other electrics and their connectors. AFM & CAS, primarily. If you try that Chinesium AFM, drive it around on low load until it is properly hot, but do'nt give it more load than you have to, except when you need to see if it will still miss. I'm dead serious about the untrustworthiness of the calibration of those copy AFMs.

Injectors are unlikely to get hot unless the fuel is coming back around hot. You could try squirting them with compressed air or freeze spray to cool them back down to see if they are maybe the cause.

[Dose Pipe Sutututu]

Some troubleshooting, connect up a timing light/gun with a proper ignition lead on coil 1. Hold the revs at 4~4500rpm and see if your timing is all over the shop, scattering off its tits.

If so, there's a high chance your CAS is fked.

But I read you have a Link ECU ready to go in, why not just skip all this and put that in - will make troubleshooting so much easier.

 

[Duncan]

Also possible you have a fuel pump or regulator issue, it runs OK when it is trying to be rich when cold, but runs badly/lean once it is trying to run normal. Put a fuel pressure gauge into the feed line and check that too.

[MBS206]

My first thought after reading first post was, did you set the ignition timing properly, especially after removing the CAS.

[uchoa]

14 hours ago, GTSBoy said:

Seeing as you have replaced the coils, that could/should rule them out. But I wouldn't always assume so. Were the coils genuine? Or is there a chance you have bought some counterfeit Chinesium shit?

Then we're back onto loom connections. They can fail when warm/hot for the same reasons. Inspections, cleaning of contact surfaces, ensuring that terminals are fully inserted, etc etc, are all justified.

The same (heat effects) holds true for the other electrics and their connectors. AFM & CAS, primarily. If you try that Chinesium AFM, drive it around on low load until it is properly hot, but do'nt give it more load than you have to, except when you need to see if it will still miss. I'm dead serious about the untrustworthiness of the calibration of those copy AFMs.

Both Coils and Loom are OEM from the dealer.  I have not tried the Chinesium AFM. I Might today.

14 hours ago, Dose Pipe Sutututu said:

Some troubleshooting, connect up a timing light/gun with a proper ignition lead on coil 1. Hold the revs at 4~4500rpm and see if your timing is all over the shop, scattering off its tits.

If so, there's a high chance your CAS is fked.

But I read you have a Link ECU ready to go in, why not just skip all this and put that in - will make troubleshooting so much easier.

 

Will get a timing gun to check this, to be honest I been meaning to check the timing because everything timing related is as the car came from Japan, being set by whatever shop did the timing 1.5k miles ago.

11 hours ago, Duncan said:

Also possible you have a fuel pump or regulator issue, it runs OK when it is trying to be rich when cold, but runs badly/lean once it is trying to run normal. Put a fuel pressure gauge into the feed line and check that too.

I believe it is running rich all the time actually, as the pops and bangs feels like unburnt mixture in the exhaust. But I will check the pump and regulator. PS also new OEM fuel filter is in during the maintenance before these slew of misfires started.

9 hours ago, MBS206 said:

My first thought after reading first post was, did you set the ignition timing properly, especially after removing the CAS.

Cas been placed on the same position as it was before removed, same markings that were left by the shop that did the timing before I bought and imported the car.

Thank you all for the responses so far by the way. Seems like I need to pay more attention to CAS condition and timing. Will check on that and report back here.

[uchoa]

Alright, cautiously optimistic update.
Tried the Chinesium AFM and it fixed. The AFM that came with the car is confirmed buggered.
Which now lands me on a crossroads. Get new OE AFM or delete it altogether and move to the link ECU using MAP.

For now I will do some more testing with the glorious made in china one before the return window closes. And then update here with final findings in case it is a reliable fix. To serve as future reference.

[MBS206]

8 hours ago, uchoa said:

 

Cas been placed on the same position as it was before removed, same markings that were left by the shop that did the timing before I bought and imported the car.

Put a timing light on it. It doesn't take much and timing is out. Out too far either way can lead to catastrophic failures.

[Duncan]

Good news. Leave the AFM on there until you move to the Link, it will use MAP instead

[GTSBoy]

Yes. Drive cautiously. Stay away from boost as much as possible. Should be OKish until Link, following advices above.

[uchoa]

Okay. Final round of testing done. Got a friend to hook up a fancy scanner to the car and we also ran some compression and leakdown tests, she is healthy. 

The MAF was definitely the culprit. So for future reference anyone with similar issues that find this thread. I suggest the following steps, in order of affordability:
 

1. Check your spark plugs for any fouling, replace plugs if they are bad or re adjust the gaps making it narrower (0.8mm would be good).
2. Check every coil's resistance with a multimeter. It can be done by probing the IB and G pins on the coil pack. Resistance should be around 1.4 (+/- 0.1) Ohms
3. Check the MAF. If you have Nissan connect or a good scanner with the 14 adapter it should allow you to see the voltage on the MAF reading should be around 1.1 - 1.2V when car is idling. But if you don't, buy a new MAF from Amazon and test, then return it. (For instance, I got a Chinese one for $40 that was reporting 1.3v on idle).
4. If you still have scanner, you can run tests on the injectors to see if they are working, just remember to unplug the fuel pump fuse/relay and have no pressure on the line. Then listen for the noises that the injectors make. Clean/replace injectors as needed.
5. Once you find the issue and fix, order thousands of dollars worth of OEM parts to refresh unrelated things (Optional)

 

PS: Thanks to the absolute legends of this forum for the responses and help to someone that went a bit over their head. (me)