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

[VancouverR34]

16 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 - Is there a good mount point or just have it hanging on the hose? I see fuel pressure guages for sale in 0-15PSI and also 0-100PSI, which one should I get?

Edited May 24, 2023 by VancouverR34

[robbo_rb180]

1 hour ago, VancouverR34 said:

For the fuel pressure guage - Is there a good mount point or just have it hanging on the hose? I see fuel pressure guages for sale in 0-15PSI and also 0-100PSI, which one should I get?

get some extra fuel line and a T piece, a 0-100 psi guage.
Ziptie it to windscreen wiper or somewhere you can see whilst driving.

For resistance leave one end on battery Negative post then check all cables to chassis and engine and engine block.
You can even check the resistance of the fuel pump windings, I don't know what they are for a stock fuel pump.

[joshuaho96]

19 hours ago, VancouverR34 said:

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.

 

P1320 is basically a signal fault between the ECU and the coilpack. Make sure the connections are solid there. I have had a connector subtly work itself loose ever so slightly causing a no-start condition.

I would investigate a few different theories here. One is you have a fueling issue as others have mentioned. Could be your FPCM dropping out, fuel pump, etc. A misfire will cause raw fuel in the exhaust regardless, even if it is leaning out you'll smell the gas. As others have mentioned you can try the somewhat sketchy method of putting fuel lines to a fuel pressure gauge and then somehow tying it to the windshield wipers so you can see it as you drive. Or running it into the interior. Obviously the "correct" way is to use an electric sensor for pressure and run the wires into the firewall grommet and then wire up the gauge that way but if you're only planning on running it like this for like one or two diagnostic drives it's maybe ok.

The other theory I have is maybe your camshaft drive pin for the CAS or possibly the internals of the CAS itself is worn out causing the ECU to really lose the plot as far as setting correct ignition timing goes. If you can get it to reproduce revving in neutral at all you can get a timing light on it and use NDS1 to lock ignition timing to something safe like 15 degrees. If it goes completely haywire at random, skipping ignition altogether or jumping like 20 degrees that would definitely cause the symptoms you're talking about.

[Dose Pipe Sutututu]

Wow you went tits out replacing parts, spent more that just fitting up a Haltech lol.

[joshuaho96]

On 5/23/2023 at 3:10 PM, GTSBoy said:

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.

I checked the parts diagram, it's really there and it is listed as a camshaft sensor on the EPC. It is also actually connected to the transmission, not a cam cover or whatever that drawing is supposed to be. Checking the FSM shows that it is a "ring gear crank position sensor", that bit under the conrod drawing is not present in any other version of the NEO engines:

[VancouverR34]

23 hours ago, robbo_rb180 said:

get some extra fuel line and a T piece, a 0-100 psi guage.
Ziptie it to windscreen wiper or somewhere you can see whilst driving.

Thanks, will buy a 0-100 psi guage and will report back once tested

23 hours ago, joshuaho96 said:

P1320 is basically a signal fault between the ECU and the coilpack. Make sure the connections are solid there. I have had a connector subtly work itself loose ever so slightly causing a no-start condition.

I would investigate a few different theories here. One is you have a fueling issue as others have mentioned. Could be your FPCM dropping out, fuel pump, etc. A misfire will cause raw fuel in the exhaust regardless, even if it is leaning out you'll smell the gas. As others have mentioned you can try the somewhat sketchy method of putting fuel lines to a fuel pressure gauge and then somehow tying it to the windshield wipers so you can see it as you drive. Or running it into the interior. Obviously the "correct" way is to use an electric sensor for pressure and run the wires into the firewall grommet and then wire up the gauge that way but if you're only planning on running it like this for like one or two diagnostic drives it's maybe ok.

The other theory I have is maybe your camshaft drive pin for the CAS or possibly the internals of the CAS itself is worn out causing the ECU to really lose the plot as far as setting correct ignition timing goes. If you can get it to reproduce revving in neutral at all you can get a timing light on it and use NDS1 to lock ignition timing to something safe like 15 degrees. If it goes completely haywire at random, skipping ignition altogether or jumping like 20 degrees that would definitely cause the symptoms you're talking about.

Connections on the coil packs and ECU are solid. Redid them while trying all the coils first having just two brand new coils and then reconnected them all when got four more coil packs. Also noticed a small plastic piece broken off on one of the connectors to one coil pack and to make sure that's not the cause - replaced wiring harness to the coil pack with a brand new one. Also to eliminate the issue of ECU (one of the sparkplug holes was filled with water and I thought if it shortned anything, maybe ECU got a fried resistor or chip) I bought a good working ECU from HR34 for a "hard not to buy" kind of price to test it out. So connections to the ECU are solid too.

For the gauge to connect to windshield wiper - no need to do that as I don't need to drive the car to recreate this issue. Just idling on my driveway after a couple minutes of running i can see this. So I can perfectly monitor fuel pressure while the gauge is under the hood. 

Also just to add, son was buying premium gas for it but he said this started pretty much soon after he filled it up with regular gas. It was then refilled again with premium but that didn't fix it.

Theory of bad internals of CAS - I don't think so as I tried a different working CAS. So I can reproduce the issue with the original and with another used but working CAS and I can reproroduce it without revving up as it happens while idling.

22 hours ago, Dose Pipe Sutututu said:

Wow you went tits out replacing parts, spent more that just fitting up a Haltech lol.

Not sure what Haltech is, probably a scanner/monitor. I got a code reader NDS1 connected to consult port but it's not helping me much. I didn't want to go that far replacing all these parts but P1320 was obviously taking me to ingnition which is why I tried coil packs and spark plugs first. Then MAF and then after that it wasn't too much expensive to add CAS and after that not too much more to add AICC and some other sensors. It wasn't planned to buy all these parts right from the start. Just taking it to dealership or a shop in Canada where they never see Skylines would probably result in losing way much more money and most likely end up still not getting it fixed.

Edited May 25, 2023 by VancouverR34

[GTSBoy]

29 minutes ago, VancouverR34 said:

Also just to add, son was buying premium gas for it but he said this started pretty much soon after he filled it up with regular gas. It was then refilled again with premium but that didn't fix it.

Starting to sound like you need to worry that he pinged it to death while it was running on lawnmower fuel. Such damage is rapid and irreversible.

[joshuaho96]

9 hours ago, VancouverR34 said:

Thanks, will buy a 0-100 psi guage and will report back once tested

Connections on the coil packs and ECU are solid. Redid them while trying all the coils first having just two brand new coils and then reconnected them all when got four more coil packs. Also noticed a small plastic piece broken off on one of the connectors to one coil pack and to make sure that's not the cause - replaced wiring harness to the coil pack with a brand new one. Also to eliminate the issue of ECU (one of the sparkplug holes was filled with water and I thought if it shortned anything, maybe ECU got a fried resistor or chip) I bought a good working ECU from HR34 for a "hard not to buy" kind of price to test it out. So connections to the ECU are solid too.

For the gauge to connect to windshield wiper - no need to do that as I don't need to drive the car to recreate this issue. Just idling on my driveway after a couple minutes of running i can see this. So I can perfectly monitor fuel pressure while the gauge is under the hood. 

Also just to add, son was buying premium gas for it but he said this started pretty much soon after he filled it up with regular gas. It was then refilled again with premium but that didn't fix it.

Theory of bad internals of CAS - I don't think so as I tried a different working CAS. So I can reproduce the issue with the original and with another used but working CAS and I can reproroduce it without revving up as it happens while idling.

Not sure what Haltech is, probably a scanner/monitor. I got a code reader NDS1 connected to consult port but it's not helping me much. I didn't want to go that far replacing all these parts but P1320 was obviously taking me to ingnition which is why I tried coil packs and spark plugs first. Then MAF and then after that it wasn't too much expensive to add CAS and after that not too much more to add AICC and some other sensors. It wasn't planned to buy all these parts right from the start. Just taking it to dealership or a shop in Canada where they never see Skylines would probably result in losing way much more money and most likely end up still not getting it fixed.

If the compression test was done after the problem started I would definitely borescope the low cylinders to look for signs of detonation like damage to cylinder walls, that's a pretty critical detail. 20% difference between highest and lowest is not great. It's kind of unfortunate you parts cannoned everything but at least you didn't pay mechanic labor which would've made this sky-high in expense.

[VancouverR34]

6 hours ago, joshuaho96 said:

If the compression test was done after the problem started I would definitely borescope the low cylinders to look for signs of detonation like damage to cylinder walls, that's a pretty critical detail. 20% difference between highest and lowest is not great. It's kind of unfortunate you parts cannoned everything but at least you didn't pay mechanic labor which would've made this sky-high in expense.

The difference in octane number between regular and premium gas here is only about 4 octanes. So it's more about 4% difference rather than 20% in gas type. I'll do the fuel pressure and resistance first before going down to removing a spark plug and examining cylinder walls. it's a pain to remove the intake to get to the coilpacks

[joshuaho96]

1 hour ago, VancouverR34 said:

The difference in octane number between regular and premium gas here is only about 4 octanes. So it's more about 4% difference rather than 20% in gas type. I'll do the fuel pressure and resistance first before going down to removing a spark plug and examining cylinder walls. it's a pain to remove the intake to get to the coilpacks

I’m saying your reported compression test values show a 20% difference between the highest cylinder and lowest cylinder.

[VancouverR34]

7 hours ago, joshuaho96 said:

I’m saying your reported compression test values show a 20% difference between the highest cylinder and lowest cylinder.

ahh, ok, thought you were talking about fuel. 

[GTSBoy]

11 hours ago, VancouverR34 said:

it's a pain to remove the intake to get to the coilpacks

It's not. It takes 10 minutes.

[VancouverR34]

I have a little update after resting resistance and adding a fuel pressure gauge. The car has been sitting without starting for a while by now and this time things were different. I was so used to starting it on my driveway and within a couple of minutes feeling the engine shaking at times that I just knew I could replicate this issue at any given time. Well, surprise this time. 

First of all I checked resistance between the negative on the battery and bolts connected to the chassis and then to different spots on the engine - it was good - everywhere around 0.1.

Then I added a fuel pressure gauge and started the car - pressure went up to 40PSI and was holding it while idling. Waited for the car to warm up and the engine to my surprise wasn't randomly shaking. It finally shook a couple of times but that was it. The car warmed up - fuel pressure showed around 35PSI while idling with transmission set on "parked". I asked my son to take it for a drive around some blocks and it wasn't shaking. After he did that a couple of times we decided to take it on a highway and do a short trip to the next exit and back. Right after getting onto the highway it started shaking and since that wasn't on my driveway this time I couldn't check the fuel pressure this time. The whole time before this I could replicate this on my driveway but not this time. So, having a fuel pressure gauge on a wiper and watching it while driving would be handy for sure. When getting home engine shaking could be felt at different times in city driving but not constant, when parked after getting home it wasn't shaking anymore. Tried to accelerate while parked and fuel pressure went down to about 32PSI. What is it supposed to be? Let me know who knows.

Also, the whole time while driving it we had a reader connected to ECU and found that O2 sensor readings were going up and down all the time while steadily maintaining speed. O2 readings would fall to 0 and stay at 0 if you remove your foot off the gas pedal. That fluctuation of O2 readings while driving didn't seem right. Let me know if that could be the cause of my issues. I'll put a video of the readings for O2 from driving it here. 

[joshuaho96]

6 hours ago, VancouverR34 said:

I have a little update after resting resistance and adding a fuel pressure gauge. The car has been sitting without starting for a while by now and this time things were different. I was so used to starting it on my driveway and within a couple of minutes feeling the engine shaking at times that I just knew I could replicate this issue at any given time. Well, surprise this time. 

First of all I checked resistance between the negative on the battery and bolts connected to the chassis and then to different spots on the engine - it was good - everywhere around 0.1.

Then I added a fuel pressure gauge and started the car - pressure went up to 40PSI and was holding it while idling. Waited for the car to warm up and the engine to my surprise wasn't randomly shaking. It finally shook a couple of times but that was it. The car warmed up - fuel pressure showed around 35PSI while idling with transmission set on "parked". I asked my son to take it for a drive around some blocks and it wasn't shaking. After he did that a couple of times we decided to take it on a highway and do a short trip to the next exit and back. Right after getting onto the highway it started shaking and since that wasn't on my driveway this time I couldn't check the fuel pressure this time. The whole time before this I could replicate this on my driveway but not this time. So, having a fuel pressure gauge on a wiper and watching it while driving would be handy for sure. When getting home engine shaking could be felt at different times in city driving but not constant, when parked after getting home it wasn't shaking anymore. Tried to accelerate while parked and fuel pressure went down to about 32PSI. What is it supposed to be? Let me know who knows.

Also, the whole time while driving it we had a reader connected to ECU and found that O2 sensor readings were going up and down all the time while steadily maintaining speed. O2 readings would fall to 0 and stay at 0 if you remove your foot off the gas pedal. That fluctuation of O2 readings while driving didn't seem right. Let me know if that could be the cause of my issues. I'll put a video of the readings for O2 from driving it here. 

O2 fluctuating like that is normal. The sensor is basically like a light switch in the response curve. The moment you go lean it drops towards 0V, the moment you go rich it shoots up to 1V. Right at stoichiometric it will be roughly 0.5V. The way the fuel control works is basically bumping the fuel trim rich when the O2 voltage drops below 0.3V (30 on NDS1) and then bumping it lean when it shoots past 0.7V, trying to keep the average around 0.5V in parts of the map where closed loop fuel control is enabled. Also forgot to mention it's not unusual for idle to not move enough air for the O2 sensor to go past 0V.

Fuel pressure is supposed to drop when pulling vacuum so when the throttle is closed. If it is dropping when you are pressing on the gas pedal below what it is at idle that means you have a fuel pressure problem.

[VancouverR34]

Another little update - yesterday I wanted to install electronic fuel pressure gauge in the car so that we could see the fuel pressure while driving. Bad news - the moment the car was started - engine was shaking/jerking vs the last time when it was working totally fine even after driving it in the neighbourhood and only started showing shaking symptoms when taken to a highway. With that much jerking/shaking as was happening yesterday we didn't even try driving it. Though with the electronic fuel pressure gauge installed inside - it showed same 40PSI while idling and no change when accelerating on "Parked". 
Soon I'll get another original working MAF and will try swapping MAF to it to see if that will make any difference.