R34 RB20DE Neo - engine feels as if missfiring after warming up - need help, I think I tried everything

[VancouverR34]

Hi, my son has an RB20 Neo Skyline R34. Only 85K km. We bought it, checked oil and on the dipstick it looked like brand new - very light, not dark dirty oil so we figured out it was changed before auction sale in Japan and we would change it later. Started looking for an OEM oil filter in no rush and during that time in about two months son put about 1000km on it and then started having an issue. Car started fine, you start driving it and the steering wheel felt vibrating or shaking. I immediately thought that it was from tires but still had two old rear tires as we already replaced the front ones right away, so got new tires for the rear too - didn't fix it. Then I drove it myself and when I stopped - i felt that vibration shaking when I'm not even driving it. Opened the hood, felt the engine and it could feel it kind of jerking/shaking at times as if there is a missfire. Immediately i changed oil and it was super dirty. Also changed all the sparkplugs - didn't help. This engine shaking doesn't start right away when you start the car but you let it run for a couple minutes and then it starts happening. The hotter it gets the more you feel it.
I thought it might be a coil - tried testing resistance on all and it was very similar on all coils, none stood out. Still decided to buy two brand new oem coils and tried changing first two - didn't help, then put the old coils back in the first two and put two new in the next two cylinders, then next two and none of that made any difference. Then I thought what if there are two bad coils like 1st and 5th or 6th and by changing them by two I still might have had one faulty one, so I bought four more oem coils and by this time I had all six coils brand new - didn't help. Then I cleaned injectors and changed fuel filter too. That didn't fix it. Then I bought a new MAF and tried that. Then I bought a new rear cam sensor that's at the bottom closer to the transmission and that made no difference. Then I bought a front angle/cam sensor, not new, it was used but working - made no difference. Then got an ECU from another RB20DE Neo and tried that and that didn't help. Then I cleaned the idle air control valve, that didn't help, solenoid on it was humming so I bought the whole idle air control valve and replaced it (the new one had the same humming noise so I guess that's normal) and sure that didn't help either. Then I had two more things to try - there is a small valve stuff - SOLENOID VALVE ASSEMBLY Genuine Nissan (1495638U0A) - I got that brand new and replaced it - still the issue is there. There is another valve stuff right next to it - (Nissan 14930-AA00A - VALVE ASSEMBLY-CONTROL) - that's the last one that's i'm going to replace but I'm still waiting for this to arrive and if it doesn't fix it - i'm out of ideas. I don't think old dirty oil and late oil change would have been the cause as when it runs cold - it is not shaking and engine shaking starts only after it warms up. Now the weather is getting hotter and I can see it now shaking almost right away after starting but if this was an engine damage due to bad or lack of lubrication - I would assume I would feel it right away when you start the car, not when the engine warms up. it really does feel as if one cylinder missfires and I can't pin point it to any particular cylinder. I read on this forum about cold valve and even saw pictures on how it's supposed to look on RB25DET and read where it's supposed to be on DET and NA engines, but I looked everywhere and couldn't find it on RB20DE Neo. I think RB20DE Neo just doesn't have it. Did I try everything? 
Any ideas what else to try would be super appreciated.

[GTSBoy]

15 minutes ago, VancouverR34 said:

Then I bought a new rear cam sensor that's at the bottom closer to the transmission.

There's no such thing. So what did you change?

16 minutes ago, VancouverR34 said:

idle air control valve, that didn't help, solenoid on it was humming so I bought the whole idle air control valve and replaced it (the new one had the same humming noise so I guess that's normal)

Yup. Pulse Width Modulated solenoid will....pulse.

17 minutes ago, VancouverR34 said:

Then I had two more things to try - there is a small valve stuff - SOLENOID VALVE ASSEMBLY Genuine Nissan (1495638U0A) - I got that brand new and replaced it - still the issue is there. There is another valve stuff right next to it - (Nissan 14930-AA00A - VALVE ASSEMBLY-CONTROL) - that's the last one that's i'm going to replace but I'm still waiting for this to arrive and if it doesn't fix it - i'm out of ideas.

Neither of those should be responsible.

18 minutes ago, VancouverR34 said:

cold valve and even saw pictures on how it's supposed to look on RB25DET and read where it's supposed to be on DET and NA engines, but I looked everywhere and couldn't find it on RB20DE Neo.

That'd be the AAC/IACV that you cleaned and replaced. It has a coolant line to and from it. Open when cold, closed when coolant is hot enough. Not going to make it misfire anyway.

20 minutes ago, VancouverR34 said:

Then I bought a new MAF and tried that

if you bought that cheap from eBay, then you probably bought a fake. Clean the old one, check the solder joints on it (google all this, it's not hard) and put it back. Treat the new one with gross suspicion.

It'll either be the coilpacks (and no, you cannot measure the primary resistance of the coilpack because you cannot access it from the pins because it has an inbuilt igniter) despite you buying "new" ones. Unless you spent ~$600 on these, you probably bought fakes. .... or, it'll be a blown headgasket, or a dirty injector, or a cracked piston or ring. Maybe cracked head. Things that get worse when it warms up anyway.

[Kapr]

Hi. I have the RB20DE NEO too. Did the car feel "slow" and slugish to drive? What about "sound" do you feel/know that car goes only on 5(4) cyl?
I have something similiar and it was bad valve on one of the cyl.
It looks like you changed "half" of the engine but did you done the compression?

[joshuaho96]

17 hours ago, VancouverR34 said:

Hi, my son has an RB20 Neo Skyline R34. Only 85K km. We bought it, checked oil and on the dipstick it looked like brand new - very light, not dark dirty oil so we figured out it was changed before auction sale in Japan and we would change it later. Started looking for an OEM oil filter in no rush and during that time in about two months son put about 1000km on it and then started having an issue. Car started fine, you start driving it and the steering wheel felt vibrating or shaking. I immediately thought that it was from tires but still had two old rear tires as we already replaced the front ones right away, so got new tires for the rear too - didn't fix it. Then I drove it myself and when I stopped - i felt that vibration shaking when I'm not even driving it. Opened the hood, felt the engine and it could feel it kind of jerking/shaking at times as if there is a missfire. Immediately i changed oil and it was super dirty. Also changed all the sparkplugs - didn't help. This engine shaking doesn't start right away when you start the car but you let it run for a couple minutes and then it starts happening. The hotter it gets the more you feel it.
I thought it might be a coil - tried testing resistance on all and it was very similar on all coils, none stood out. Still decided to buy two brand new oem coils and tried changing first two - didn't help, then put the old coils back in the first two and put two new in the next two cylinders, then next two and none of that made any difference. Then I thought what if there are two bad coils like 1st and 5th or 6th and by changing them by two I still might have had one faulty one, so I bought four more oem coils and by this time I had all six coils brand new - didn't help. Then I cleaned injectors and changed fuel filter too. That didn't fix it. Then I bought a new MAF and tried that. Then I bought a new rear cam sensor that's at the bottom closer to the transmission and that made no difference. Then I bought a front angle/cam sensor, not new, it was used but working - made no difference. Then got an ECU from another RB20DE Neo and tried that and that didn't help. Then I cleaned the idle air control valve, that didn't help, solenoid on it was humming so I bought the whole idle air control valve and replaced it (the new one had the same humming noise so I guess that's normal) and sure that didn't help either. Then I had two more things to try - there is a small valve stuff - SOLENOID VALVE ASSEMBLY Genuine Nissan (1495638U0A) - I got that brand new and replaced it - still the issue is there. There is another valve stuff right next to it - (Nissan 14930-AA00A - VALVE ASSEMBLY-CONTROL) - that's the last one that's i'm going to replace but I'm still waiting for this to arrive and if it doesn't fix it - i'm out of ideas. I don't think old dirty oil and late oil change would have been the cause as when it runs cold - it is not shaking and engine shaking starts only after it warms up. Now the weather is getting hotter and I can see it now shaking almost right away after starting but if this was an engine damage due to bad or lack of lubrication - I would assume I would feel it right away when you start the car, not when the engine warms up. it really does feel as if one cylinder missfires and I can't pin point it to any particular cylinder. I read on this forum about cold valve and even saw pictures on how it's supposed to look on RB25DET and read where it's supposed to be on DET and NA engines, but I looked everywhere and couldn't find it on RB20DE Neo. I think RB20DE Neo just doesn't have it. Did I try everything? 
Any ideas what else to try would be super appreciated.

You've basically parts cannoned everything. Start with a compression test + leakdown test on all cylinders. Then do a leakdown test. Then make sure your cooling system is holding pressure and isn't leaking into a cylinder.

[VancouverR34]

On 19/05/2023 at 10:20 PM, GTSBoy said:

There's no such thing. So what did you change?

 

this is what I changed 
 

SENSOR ASSEMBLY, CAMSHAFT Genuine Nissan (23731AA010)

[VancouverR34]

On 19/05/2023 at 10:20 PM, GTSBoy said:

if you bought that cheap (MAF) from eBay, then you probably bought a fake. Clean the old one, check the solder joints on it (google all this, it's not hard) and put it back. Treat the new one with gross suspicion.

It'll either be the coilpacks (and no, you cannot measure the primary resistance of the coilpack because you cannot access it from the pins because it has an inbuilt igniter) despite you buying "new" ones. Unless you spent ~$600 on these, you probably bought fakes. .... or, it'll be a blown headgasket, or a dirty injector, or a cracked piston or ring. Maybe cracked head. Things that get worse when it warms up anyway.

MAF was purchased from an automotive store as a direct replacement to part number that Skyline uses. I think I paid about $100 for the MAF, can't remember now. 

For the coilpacks - i bought them OEM, came in OEM Nissan packaging and though I didn't spend $600, it ended up around $500 simply because I bought them from United Arab Emirates warehouse and not from Japan warehouse. Same OEM in Japan were almost twice the price. So those are real ones. Injectors were cleaned by a professional injector cleaning place - $450, filter in injectors was replaced to high flow and o-rings were replaced to new ones. 

[VancouverR34]

On 20/05/2023 at 2:23 AM, Kapr said:

Hi. I have the RB20DE NEO too. Did the car feel "slow" and slugish to drive? What about "sound" do you feel/know that car goes only on 5(4) cyl?
I have something similiar and it was bad valve on one of the cyl.
It looks like you changed "half" of the engine but did you done the compression?

It sounds totally fine but when it jerks - you can almost feel the sound changing just for the jerking moment. Otherwise sound didn't change. And yes, I did compression test, forgot to mention that. I think sixth cylinder was the worst but not that far out from all the other ones. I have test results at home, will update the post once I get back home from work.

[VancouverR34]

On 20/05/2023 at 4:24 PM, joshuaho96 said:

You've basically parts cannoned everything. Start with a compression test + leakdown test on all cylinders. Then do a leakdown test. Then make sure your cooling system is holding pressure and isn't leaking into a cylinder.

I did compression test, forgot to list it in the original post. Didn't do a leakdown test though. Cooling system is holding pressure. 

[GTSBoy]

1 hour ago, VancouverR34 said:

this is what I changed 
 

SENSOR ASSEMBLY, CAMSHAFT Genuine Nissan (23731AA010)

Whoa. Now I need a photo of it on the actual engine. How does an RB20DE Neo have a sensor that no other RB has?

Edited May 23, 2023 by GTSBoy

[VancouverR34]

ok, I'm now home and can post compression test results. Cylinders from 1 to 6 are the following - #1 - 15, #2 - 13, #3 - 14, #4 - 14, #5 - 12.5, #6 - 12. 
Oh, and I forgot to mention that I did clean MAF before buying a new one. Will take a picture of where the rear cam shaft sensor is and will post soon.

[VancouverR34]

18 minutes ago, GTSBoy said:

Whoa. Now I need a photo of it on the actual engine. How does an RB20DE Neo have a sensor that no other RB has?

ok, if you look right behind the driver's side wheel onto the transmission almost where it connects to the engine this is what I have there - that's rear camshaft sensor

[VancouverR34]

oh, one more thing I forgot to add - when I first checked codes after my son was driving it for several days with the engine vibrating, i got a code P1320. Which explains as to why I first replaced spark plugs and then the next thing I tried was replacing coil packs with real original brand new oem nissan coil packs. Also just to make sure I don't have problems from the wiring to the coil packs - I got a brand new wiring that goes to the coil packs from that connector to the main wiring. And once that didn't fix it, then I went to check the angle cam shaft sensor and the rear cam shaft sensor. And only after that did the injectors cleaning and testing. 

[GTSBoy]

21 minutes ago, VancouverR34 said:

ok, if you look right behind the driver's side wheel onto the transmission almost where it connects to the engine this is what I have there - that's rear camshaft sensor

That's not a camshaft sensor. The cams are on top of the engine. That's about as far from there as you can get. That must be looking at the teeth on the flex plate ring gear. I did not know that NA Neos had that. If it is an engine sensor, then it is a crankshaft/engine position sensor. But even then, you can't easily have missing teeth on the ring gear (otherwise the starter motor would tear it apart) and so it cannot be an absolute engine position sensor. I'd be willing to believe that it belongs to the TCU as an input speed sensor, but I can't imagine why they would do that either, as you can (and they already do) just pass engine speed through from the ECU to TCU via the comms bus.

Anyway, new to me. Willing to bet that if you pulled it out and started the engine it would run just fine.

[VancouverR34]

Don't know what that is but went by how Nissan names it in its catalog - SENSOR ASSEMBLY, CAMSHAFT. It was only around $30 so I figured at that price it doesn't hurt to replace it too. Sure flywheel won't have missing teeth but the sensor might go bad and not read it. I thought it worked together with the front angle sensor. Either way - original one was pretty clean as actually everything including MAF and  AAC/IACV and anything else I tried. Everything is super clean and didn't make a difference. I am going to get a hold of original known working MAF and try that and would be nice to check the pins if it's easy to do. 

[robbo_rb180]

Have you plugged in and looked at what sensors are doing with something like consult?

Can you write a list of parts changed as that first post is difficult to read, separate Paragraphs help massively.

Reset Crank Angle sensor timing and unplug the knock sensor.

The key to any diagnosis is data and using consult will high light if its a sensor issue. Throwing parts at it is just guessing.

[GTSBoy]

39 minutes ago, VancouverR34 said:

Don't know what that is but went by how Nissan names it in its catalog - SENSOR ASSEMBLY, CAMSHAFT.

I think if you look at the line drawing of it you posted, you will see that it is installed on a cam cover.....on some other engine. On that installation, it would be a cam sensor. On your application, it cannot be.

The only engine position sensor that RBs need and use is the CAS (Crank Angle Sensor) mounted on the front of the exhaust cam, which has multiple sets of solts and multiple optical sensors to pick up actual engine position. Plus or minus the slop and harmonics in the timing belt, of course. Great sensor, shit place for it. But that's another story.

[VancouverR34]

3 hours ago, robbo_rb180 said:

Have you plugged in and looked at what sensors are doing with something like consult?

Can you write a list of parts changed as that first post is difficult to read, separate Paragraphs help massively.

Reset Crank Angle sensor timing and unplug the knock sensor.

The key to any diagnosis is data and using consult will high light if its a sensor issue. Throwing parts at it is just guessing.

List of parts changed:

Spark plugs

Coil packs - Nissan 22448-AA000 - COIL ASSEMBLY, IGNITION

Wiring harness to coil packs - Genuine Nissan (240795L300)

MAF - original MAF was cleane and then was replaced with not genuine but replacement part for original part number - bought from rockauto.com

AAC/IACV - Genuine Nissan (23781AA000) - used

Angle cam sensor - used

SENSOR ASSEMBLY, CAMSHAFT Genuine Nissan (23731AA010) - that weird rear sensor

Fuel filter (pitworks) - Pitwork AY505NS001 - FILTER, FUEL

Air filter - generic

Oil filter (pitworks) - Pitwork AY100NS005 - FILTER, OIL

PCV valve - Nissan 11812-41B00 - INSULATOR, PCV VALVE

Also not related but replaced valve covers gasket due to leaking oil and did an oil change.

Fuel injectors serviced/cleaned by a professional injector cleaning company n- gave them the whole fuel line with injectors

Compression test done - 1 - 15, #2 - 13, #3 - 14, #4 - 14, #5 - 12.5, #6 - 12

Coolant pressure is holding, not loosing coolant

Oil pressure is normal

When engine vibration/jerking/stattering happens, gas consumption is higher than normal and I think I can smell unburnt gas through exhaust.

Haven't reset Crank Angle sensor timing and haven't unplug the knock sensor. When putting another Crank Angle sensor I put it in the same position/angle as the previous sensor.

I did plug in a phone (Android) connected to consult port and read codes using NDSI v1.53 app but don't know what to look for specifically at what sensors are doing. Error code that initially got detected (P1320) no longer reads, son is not driving the car since I figured out this is an engine and not a suspension/tires problem. I didn't want to risk harming it more so immediately he stopped using the car after we realized this is an engine related problem. Probably if we drive it now, it would give that error code (P1320) again.

Hopefully this is easier to read than the original post.

 

[robbo_rb180]

Also put a fuel pressure guage on the fuel line before the regulator, could be loosing fuel pressure as the car warms up. The pump would be failing, heating up and slowing down flow.
Check all the grounds too, check the resistance using a multi meter

P1320 being ignition/crank signal issue

Edited May 24, 2023 by robbo_rb180

[GTSBoy]

6 hours ago, VancouverR34 said:

MAF - original MAF was cleane and then was replaced with not genuine but replacement part for original part number - bought from rockauto.com

I'm still suspicious of this. There's not really any such thing as a real "non-genuine" AFM for these things. All the non-genuine ones are unreliably wrong, or just completely wrong.

[VancouverR34]

10 hours ago, robbo_rb180 said:

Also put a fuel pressure guage on the fuel line before the regulator, could be loosing fuel pressure as the car warms up. The pump would be failing, heating up and slowing down flow.
Check all the grounds too, check the resistance using a multi meter

P1320 being ignition/crank signal issue

For the fuel pressure guage - I can't think of a good place to have it permanently mount as fuel lines come up almost middle of the side of the engine bay with a hose going right from the fuel filter to the fuel line, so I guess that would be just a temp setup to test out the pressure, or is there a good spot to have it permanently mounted? Would be nice to have it there.
For the resistance - would I be checking resistance between negative on the battery and on the engine? I myself have been wondering about possibility of the ground being the cause too.

4 hours ago, GTSBoy said:

I'm still suspicious of this. There's not really any such thing as a real "non-genuine" AFM for these things. All the non-genuine ones are unreliably wrong, or just completely wrong.

Very possible, I will have access to working parts from a 4wd skyline that runs in about three weeks, will swap one from out of there to test it out for sure if not solved by then. With parts availability in Canada this has been going over for some months by now. One package literally was held by customs for over a month. Only when I filed for refund with the supplier and they went to their UAE post and those contacted Canada post or Canada Customs - only after that it was processed the same day. For that order just took almost two months to get it. Those were actually the original coils that I was waiting for.