RB20DE NEO accelaration/cruising "problem"

[Kapr]

HI.
I try to find something about this but nothing came on...only about other things.
So.
Sometimes when iam cruising and trying to maintain the speed the vehicle...i dont know like "cut" the power and lags. But only for a split second.
Do not know if it is related but often when iam cruising and try to put a little more gas nothing happens...only after a while(1-3 secs) or when i step on the on gas little more. It happens only when cruising and trying to maintain the speed...when i driving it "harder" all is normal and no problem occurs.

What should i look for?
Coil packs are good(splitfire) and spark plugs are new.
Maybe injectors? Dont know how "good" they are or fuel pump(i know i have bad "read meter") cuz my fuel gauge works but show way less fuel (like the car had only 30-40 liter tank)

Car starts perfectly...no smoke no nothing..idle is good(around 750-800rpm)..when it drives other than that above it drives great.

Many thanks for any help 🙂 

[Murray_Calavera]

What ECU do you have?

[Kapr]

Stock 
 

[trel]

Vac leaks?

[Kapr]

DK...is there any "great" way to know for sure? Engine was partly rebuild like last year(one valve was bad and car ran on 5 cyl) back then we have a little bit of leak around intake manifold but new gasket take care of that. Now it do not seem any air is leaking but we will check again.

I drove the car today and no lag/stutter... it is very random so it is very hard to repeat.

 

[GTSBoy]

This is either going to be (in no particular order);

• Bad AFM wiring connection, or dirty AFM element,
• Bad CAS wiring connection, or possibly dirty optical disk,
• Bad fuel pump. As in, possibly dying, ore maybe it has a dodgy wiring connection. Could also be the FPCM (assuming there is one).
• Maybe bad O2 sensor, but would seem unlikely from the symptoms.

[Kapr]

AFM should be clean...but we will check again.
CAS dont know 100% but we will check too.
Fuel we check for sure...as i said it gives bad reading so maybe the "whole" pump is bad.
Yeah O2 sensor my mechanic said it should not cause this...but we can check too.

What about those injectors? Should they be the problem? I think they are "stock" from the factory and when i bought the car it was obvious there was not enough maintenance.

[GTSBoy]

1 hour ago, Kapr said:

AFM should be clean...but we will check again.

It's not just the cleanliness of the sensor element that can cause problems. Dry and cracked solder joints inside the casing, or corroded pins in the plug/socket can cause shitty behaviour.

CAS, ditto.

The fuel gauge is of no importance. The pump and the gauge have nothing to do with each other except being in the sample place. The pump might be dying and giving low pressure, either all the time or intermittently. Or the fuel filter could be shitty or fuel hose could be falling apart and causing  moving blockage. You need to hook up a fuel pressure gauge and keep it on unti you experience the shitty behaviour and see if the pressure goes to poop at that time.

Injectors could be crook. But.....as to maintenance, they are essentially maintenance free. 20 year old injectors should be fine if they haven't been fed a diet of dirty fuel. And injectors are seldom intermittent. They're either dirty or not. Although, having said that, the connectors could be a problem, as per the other items.

[Kapr]

Ok thanks.
As i said above the car was from Japan and at the state it arrived it was obvious that the maintenance was quite bad.
Iam not joking if i say that car HAD factory air filter...
Other than that car feels ok and when i drive it little bit harder no problem at all...no "lag/stutter" or hesitation of gas or anything like that...only when cruising and trying to keep same speed.

I will try check those things.

[Kapr]

Hi,
UPDATE(not o good one this time  )

Today i drove normally and suddenly i notice the engine was running kinda rough...like it was down one or two cyl. On idle it was all normal...no smoke no nothing...but when i start going car feels extremly sluggish and it was very slow even on this car. Car was kinda lagging going into the speed...as i say it looked like it was down one or two cyl.
I do not want to risk anything and went straight to the shop.
Car was completely fine on idle and even reving up the engine reveal nothing wrong...asi i mentioned above i bought new MAF(the part is exactly the same asi mine)...
So we try to replace the old one with new...but it was kinda shocking.
When we put the new...car starts but run very bad...low on idle...definetely not running on all 6 and smoking(black) from exhaust(maybe rich?)
Why the car does that? Of course the car stayed(again) at the shop and he will take a look what is wrong.

 

[JayJay777]

hey man, not sure what engine you have, but if its an Rb, my car had a similar issue. perhaps check the clamps on your rocker cover breather hose if its not your maf sensor. if its not that then maybe also check your spark plugs.

hope this was even a bit of help.

[GTSBoy]

5 hours ago, Kapr said:

i bought new MAF(the part is exactly the same asi mine)...

But is it really exactly the same? There are very convincing Chinese fakes of pretty much all of these parts. Anything you buy cheap from eBay or similar should be assumed to be fake. And the fakes do not always work as intended. Probably only a small fraction of them are any good at all. This applies to AFMs, CASs, coilpacks, igniters and just about anything else that was originally Bosch or Hitachi or Mitsubishi or JECS or Delco, etc etc.

 

And so, a (dodgy) new AFM could easily cause your engine to misbehave.

But, I would bet that it's not your AFM. You appear to have a serious set of problems on this car, and I can guarantee you that we will not be able to diagnose it across the internet. Any capable mechanic, with the car in hand, should be able to diagnose this shit. If a mechanic cannot find what is wrong on a 30+ year old engine design, regardless of it being a Jap engine that was never seen in eastern Europe, should not be called a mechanic.

The process is easy. Observe the symptoms. Listen to, feel, smell, etc, the things that are going on. Check for power and earth on things that really need it. Pull out the diagnostic code reader and see if the ECU has anything to complain about. Do some basic maintenance/cleaning of IACVs, throttle bodies, etc etc, to make sure that it's not just dirt causing problems. Pull injector plugs and coilpack plugs to see which cylinders drop the most. Swap injectors and coilpacks back and forth to see if the problem moves with them. Check cam timing, ignition timing. Look for head gasket symptoms. Look for blown exhaust manifold and turbo gaskets, inlet manifold gaskets. Check coolant pH, operating temperature, etc. Inspect oil, filter, etc. Try swaptronics with known good AFMs, CASs, etc. Hook up the oscilloscope and observe CAS signals.

And so on. And I'm not even a mechanic. Imagine how many more things a mechanic could list to look into.

[Kapr]

@JayJay777 Hi. I try to check that 🙂 

@GTSBoy It is this MAF https://www.ebay.com/itm/283856838638 it looks genuine to me but i do not know 😕
Yeah he is good i just want to "help" and try to get some info for mysefl too 🙂 
He put that engine back to the working state at it was working fine. (minus those problems) But maybe now he will figure out the problem and even on cruise car will be "normal".

But thx for the info...i will let you know what is/was wrong 🙂 

[GTSBoy]

Erk. I dunno. It might be genuine, but it is very cheap. Very cheap and genuine are not compatible. My presumption is that any such part on eBay is fake, even if they promise you on their sister's virginity that it is genuine.

[niZmO_Man]

$90 might as well. Better than paying $500

[Kapr]

I dont know too...i looked at the "original" price from JP Parts at is around 500 USD...but many times these are price are way to high.
Hope i wont need to buy that 500 USD one 🙂 

I tried to look on different parts but the part number is the same...this MAF is used in tones of other vehicles.
The number on the silver plate is different but i do not know what is that for...
 

Edited May 12, 2023 by Kapr

[Kapr]

EDIT:
Hi...so the "new" MAF is busted...100% not working or is just a cheap knock off...my old one running fine but soon as we put the new one car start to behave like that above(black smoke rough idle and 1-2 cyl down)...
So at least my is "good" for now.

Another issue related to the problem is that we found one of the coil connector was little bit out and it seems kinda broken.
He says that this should be that problem cuz car is running normal until it heats up and then it start running bad. He says it can for like 90% could be this bad connector. It heats up and then just "slide" out. He try to "repair" just for the testing if it is really the connector. I already buy a new harness 🙂 
So we will see.

[Duncan]

Well, full marks to GTSBoy in internet guess troubleshooting then!

[Kapr]

Yeah the man has some serious knowledge 🙂 
I let you know how the things went after the reapir/loom arrives...
I know that very few people has this engine...but at least it will be there as a info...not much of it anyways so at least something.

[Kapr]

Hi,

So the new coilpack loom solve the problem.
But the "cruising" problem is still there...the "lag" happens only a little bit but (it maybe connected) this happens mainly on 4th gear...there is a lag in power. When i try to accelerate only to maintane speed or little bit speed up...nothing happens only after a few moments like the car would "forget" what i want him to do. But if i put "peddal to the metal" it behaves normaly and quickly.

When we replace the coilpack loom we changed sparked plugs(old were still good and nothing bad bud still) checked the coil packs and injectors...all were good.

So what can it be? Can it be that MAF? And if...is there any other place i can try to get it other than the "official" sites with nissan parts(they want like 500USD juts for the part) 😄

Thx 🙂