S2 Rb20det Leaning out badly

[Empire087]

Ok so ive been troubleshooting My car for the last 6-7 months, Basically ive had an issue that over a short period of driving:Generally 5-10 minutes my car will start a lean cut out and slowly get worse until its a 2500 rpm cut and it will sometimes climb over that. It happens at around 4k rpm, but it comes on after some spirited driving sometimes faster than others but always comes. Essentially I will get on the throttle for a few times and do a few good pulls then the car will start just going max lean all the time when throttle is applied. The first bit of it is at 3700-4000 rpm, and its it will lean bog Max at 18 afr ---. Then it will get to the point where you can barely give in any throttle without it cutting out Like 1/16 of the pedal. It will always happen, sometimes it takes longer than others. However if i turn the engine off and on the problem will simply go away for a short period and come back. Also to note the car runs rich 10.5ish afr at wfo, and cruises at around 13. So far ive tried/replaced: ecu(Mine is blitz access with custom rom R32mt, One i have is a rom tuned for an r32 a/t)No difference, Another cas NO difference, Brand new plugs, Clean/taped coil boots, Different Ignitor NO difference, Another Maf NO difference, 98 sentra cts, 98 ka cts both no difference, New 255 fuel pump(2), Different Fpr(both tested good), multiple fuel filters, checked injectors all 14ohm, checked tps at .46 idle/around 5.0 wfo, and deleted my cold idle valve. The weird thing is if i restart my engine(Key all the way off) and turn back on the problem goes away for a little while but comes back as before. The car also starts like s***, not quite sure why, im pretty sure i wired the start signal in right.
Video below
https://www.youtube.com/watch?v=9kWXgqNlED4

Ive been struggling with this for the last 6 or so months i really need some help!

[baube]

do you have your o2 still plugged in? I had a similar problem with a tuned ecu. I had to unplug the o2 and everything was fine then

[Empire087]

Well ill certainly give it a try, damn near tried everything else lol.

[Empire087]

Well that didnt work either.

[lgsr20swap]

Does ur wideband have a failsafe?? Maybe the wideband is fucked??

[Empire087]

Oh it bucks and falls on its face, its certainly going lean. Its an aem wideband which is like 3 weeks old.

[cotbu]

Stop driving the car like that, and when you make videos turn the phone vertically.

I can probably help you, but I'll be requesting videos and I like full screen videos, lol. So pull codes and report back. If you don't want my help, tell me to go screw myself!

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[Empire087]

Usually i take proper videos, that was just a poor timing one. The thing is im throwing no codes, its showing up a code 55.

[cotbu]

Your ecu could be bad, try throwing a code.

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[Empire087]

It will indeed throw a code, i unplugged the tps and it came up with a code 43 yesterday. Also tried an auto r32 ecu as apposed to my blitz access mt r32 ecu and it told me code 54 for no auto signal.

[boosted23]

Have you checked your mass air flow for anything on the wire or for issue? Check your tubing to make sure it's sealed and check the waste gate vacuum line.

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[Empire087]

The previous owner did kind of a janky job wiring the mass air flow extension. I redid the wiring from that point with shielded wire.

[baube]

did you checked the solder inside the maf? they tend to crack sometimes

[Empire087]

Resoldered both at the connection

[Empire087]

Someone has to know something.

[boosted23]

You should really try another maf. Maybe even go 300zx maf.

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[cotbu]

I agree if he's not sure what mafs the ecu is tuned for, try the most popular. Most likely its tuned for a stock mafs or z32.

Op if you have a way to dump the bins I can tell you what mafs its tuned for, and tell you if you have the correct injectors.

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[Empire087]

I have tried another maf, i have two j60s. The guy that sold me the motor set told me it was tuned for stock injectors, and stock maf.

[cotbu]

You're trying to diagnose a problem with your car, you can't go back and say things like the previous owner did a janky job on wiring the mafs, then be like he told me it was tuned for.... or it ran good when...
all that must go out the window if you want to fix your car or just ask the previous owner for help! I would prefer you go back as close as possible to stock, because we know how stock should function. Does that make sense?

I forgot you said you be at this for 6/7months, time to be proactive.

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[Empire087]

Ok, so the j60 was stock, ive tried two. I will see if i can find a z32. I have been tearing this car apart trying everything under the sun so far. The injectors are stock.

How would i go about checking the ecu bin? As of now, i have no means to do that. But i also have that other r32 A/T ecu which brings the same problems. That was tuned for stock maf/stock injectors.

I was told the engine ran great when he had it, and as ive been tearing into the motorset/wiring harness ive been finding things i didnt like. so ive been fixing them. Ive been being proactive with this the whole time. Im simply running out of potential fixes to the problem. I made the list of things ive tried/changed so far.

[cotbu]

2500rpm limiter or breakup seems and or problems around there are usually mafs problems, and they come with codes. so let's start there.

your wiring for the mafs, it doesn't need to be shielded wire, but if you use shielded wire the shield cannot touch the signal wire at all because the shield is grounded. verify that and repair if necessary.

post a better video of your gauges and rpm, or data log while the issue is happening.

if you have a consult port wired up, cable and software you can data log through it and also download the bins in the ecu.

I'm thinking mafs issue, so I'd start with the wiring, visual. Then open the ecu, follow a pin out and check continuity from ecu pins to mafs plug. against ground as well, making sure there's no tone from signal to ground. make sure the ecu will throw that mafs code, on whichever ecu you believe works.

How do the plugs look after this?

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[Kingtal0n]

If I bought a car with an RB and right away it seemed to be leaning out, I would

A: immediately tune-up the engine and fuel system, check fuel pressure during WOT

Next,
B1: switch back to stock ecu/maf/injectors if still using the stock turbo
B2: if using an upgraded turbo, it must have a stand-alone, add fuel manually, or
B3: If using an upgraded turbo and a rom-tune, invest in a stand-alone (cheapest is PFC for $500~ for that engine used) *OR* [Raise fuel pressure / Install a piggyback] for spot adjustment as a temporary band-aid to bring the air fuel ratio back. A combination of both would be ideal. For instance if the car is going 15:1 at 15psi of boost and my base fuel pressure is set to 43.5psi, I would raise it to 58psi and that should bring the a/f down some (closer to high 13's) - if it did not, I would suspect the fuel pump is the culprit. If it does, then proceed to add the rest of the gas with the piggy back (until you can get a stand-alone). The piggyback/fpr solution is only reliably viable at "low"(5-12psi) boost, with close-to-stock size injectors, on a mostly stock engine.


Another test to see if your fuel pump is the culprit would be to create a boost leak somewhere and go WOT. IF the air fuel comes back rich then you see you have the gas available from the pump. If the engine stays the same lean ratio / maf cuts then you have your answer (fuel pump output)

[cotbu]

It seems like he eases into throttle and it still happens, maybe if he disconnects the waste gate, or tries a zero boost test, we could further eliminate some causes.
If this was happening arount 4/4500rpm I would say fuel/fuel pump related.

OP post a picture of you engine bay too.

[Empire087]

Will do tommorrow, i did pull my injectors/rail to make sure there was no junk in the rail or injector screens. Im also going and renting a fuel pressure gauge, so i can check that out.

[Empire087]

Was pouring here all day, so i wasnt able to go out for a drive.

here the pic of my engine bay
https://farm8.staticflickr.com/7732/17954655369_4f88512257_b.jpg

[boosted23]

You really need an air filter on your maf

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[Empire087]

I literately tried it to see if maybe the air filter was causing problems. I just havent put the filter back on.

[cotbu]

so........., is that how the engine looks now and how you've been driving it except for the filter?

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[Empire087]

yup, except i replaced the hoses on the pcv and put the filter back on the other port.

[cotbu]

Yeah cause the hose missing from the intake manifold side, could have explained the whole thing, but running a filter on the port isn't the best setup, even through everyone does it. The other issues I see are wiring. If you're not having hard starts or rich idle then maybe some of its OK.

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[Empire087]

I have been having issue with hard starts, but usually it idles correctly.

[baube]

the "open" valve cover with a filter doesn't help for sure

I can see my a/f going lean only by opening the oil cap at idle

[Empire087]

Ok i have some videos, hopefully they do an ok job showing what the fuel pressure is doing. It is indeed losing pressure.
Heres the car crusing, it does go to about 13.1 or so after being off the throttle a while. This is with almost zero pedal pressure, as its low rpm
https://www.youtube.com/watch?v=5rgwy_LUHfQ
This is the problem happening.
https://www.youtube.com/watch?v=qTQzgU6x8Ww
and here is showing that if i shut the car off the problem goes away(temporarily)
https://www.youtube.com/watch?v=pkOX4M6AJPw

[R_34]

How much volts do you have at the pump ?
The hose going from the plenum to the fpr is not leaking under boost ?

[Empire087]

The battery is wired directly to the pump, and the ground directly to the chassis. Using a relay as the on/off.

[Kingtal0n]

So you've narrowed it down, good. Next step would be to pinch the return line shut (clamp it closed) and see if fuel pressure skyrockets, and stays there.

Also check the regulator make sure the vacuum hose is connected and functioning.

If you clamp the return line shut, and fuel pressure still drops / stays low, then your pump is bad, or there is a major clog between the pump and rail. given the intermittent nature it is more likely pump. Checking the voltage is advised but somewhat unnecessary, since the fact the pump works at all indicates that there is some connection (at least 8+volts IMO), and a wire so small that it would not support pump activity would just burn or the pump would stop all together. In other words, if we run any car battery down dead, just leave the headlights on all day. When its dead, let it sit a while, then run the smallest wire to the rear of the car and still notice there is probably at least 8volts.

[cotbu]

how is that relay controlled? can you do another test, just cutting off the relay and powering it back on to see if it changes anything.

if you ever ran the pump dry, I would consider replacing but after that test. lol

I only ask because I couldn't see, if pressure went to zero when you did the key off, while rolling. You moved the camera as I was watching the gauge. I think you got it figured out though.

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[Empire087]

Already still having problems, except i found out that those gauges your rent from the auto parts store suck. After returning to autozone to bring them their gauges back, that essentially just got stuck on zero after a while :/. During that drive after changing the power source for the on signal for the relay, the problem came right back as usual. Shutting off the car would temporarily fix the problem. So i borrowed the same gauge form oreileys and that one showed things working right for a little while, and then slowly got lower and lower until it didnt move right anymore and got stock on like 20 psi until i bleed it. The problem still persist after all that, and i switched over to a different fpr to try and fix the problem.

Ok i checked the voltage at the batter 13.8v, and then checked the voltage at the pump it was 13.3/4 volts. This was taken using the pumps ground. with the gauges acting the way they did i clamped the return line and it seemingly made no change in the gauge. I couldnt however tell if the fuel pressure went up.

Cotbu, the fuel pump is like 2-3 weeks old and ive never driven past 1/4 tank. Im wondering if im on my second dud. I will try and cut the power tommorrow and see if that makes a difference. Also You wanted to know if my ecu will throw a maf code, it indeed does.

Just trying everything, im getting beyond frustrated.

[Empire087]

Alrighty rehooked up the gauge, with the original fpr im getting about 40 psi at idle and around 50 with the vacuum removed. I used a jumper to bypass that relay and just run 12v direct from the battery.

[Empire087]

Brand new pump, and a rb25 fuel pressure regulator still has the same problem.

[cotbu]

Still having issues? Have you looked inside the ecu yet? Can you tell me if you have a daughter board inside with socketed chips or if you are able to remove the board from the ecu?

I'd like to try to richen up the transition area of the map only and see if you still end up leaning out.
That could be a last resort if you prefer, cause before that I would rewire the whole swap, double checking the work.
Systematically eliminating things as the cause.

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[Empire087]

Yup still having the same issue, but i did remove the ground from the harness and ground it right by the tank for the fuel pump. It seemed like it took longer to lean out. Im also running pig rich cruising 12:1 afr, max of 10.5/6 wfo it actually bogs sometimes its so rich wjen you lay into it. And it settles around 13.8 afr at idle. While warming uo theres also a pretty bad miss that goes away forr the most part once above 140 degrees.

My ecu is rom chipped, but i did try an r32 a/T ECU and the problem followed the ecu.

[Kingtal0n]

you didnt need to change the fuel pump until you clamped the line shut, as instructed above,
If you clamp the return line shut, and fuel pressure still drops / stays low, then your pump is bad,

you are making more work for yourself by ignoring procedure

[Empire087]

Ok, heres the thing though. The parts store fuel pressure gauges are junk, I couldnt even start to try and trust one after fucking with those things over 5 days. I understand what your saying make sure the fpr is good, however to my knowledge a fuel pressure regulator either works or it doesnt correct? Even so i took two that are proven working and replaced my stock one with both of those. One off a ka24e, and one of a rb25det. my problem still persist, The pump was under warranty it was worth a shot for 25 minutes of time to change it out. The fact was i had to make the pump physically stop running to get any kind of pressure back potentially pointed towards a faulty pump.

[Empire087]

Ok definetly green relays, today while i was out for a drive after it started breaking up a little that it wanted to die when i came to stops. And it came really close one time and then the problem again temporarily went away. I didnt have to restart the engine anything the rpm just got really really low. Thoughts?

[Empire087]

you didnt need to change the fuel pump until you clamped the line shut, as instructed above,

you are making more work for yourself by ignoring procedure

Ok so i did clamp off the return line and the pressure does increase to about 90 psi. However if i rev it, then the fuel pressure drops off incredibly fast and falls well below 20 psi. So this would point at the pump correct?

[Kingtal0n]

Ok so i did clamp off the return line and the pressure does increase to about 90 psi. However if i rev it, then the fuel pressure drops off incredibly fast and falls well below 20 psi. So this would point at the pump correct?


I thought you changed the pump?

1. unplug the vacuum hose from the fuel pressure regulator, with the engine off, and run the fuel pump. Write down the pressure.

2. run the engine with the regulator vacuum hose connected. At idle, the fuel pressure will be lower, by about 6-8psi (for engine vacuum around 12-15" Hg).

3. When you "stab the throttle" or "rev the engine" the fuel pressure should return momentarily to the fuel pressure from #1, as the engine vacuum drops back to 0" Hg (0psi).

4. After you let off the throttle, the engine vacuum shoots to 18-22"Hg and the fuel pressure should now drop below what it was in #1, and then gradually settle back to where it was in #1 at idle.


Clamp the fuel pressure line and go for a drive- See if the fuel pump can deliver enough fuel to keep the engine rich, and keep fuel pressure high. 90psi is hard on fuel system components but it should be fine for a quick test. You just want to prove that the pump is unable to supply the demand. e.g. If I SEE 90psi of fuel pressure at 12psi of boost and 6000rpm and I SEE that now the air fuel ratio is much much lower, then I KNOW the pump is able to supply for the demand, and I can direct my attention to the computer or elsewhere.

[Empire087]

It does all those things listed 1-4. pressures are 39 psi at idle(21 psi vacuum), and 46/47 no vacuum pressure. And yes if i downshift while cruising and pull more vacuum it will drop 2-3 psi more than it was at idle.

[Kingtal0n]

It does all those things listed 1-4. pressures are 39 psi at idle(21 psi vacuum), and 46/47 no vacuum pressure. And yes if i downshift while cruising and pull more vacuum it will drop 2-3 psi more than it was at idle.


ok so what about #5, clamp and drive