SR Stutter and miss when engine is warm?

[BlackZenkiS14]

Originally Posted by inopsey

are you able to read the voltage of the tps with the ecu, on a laptop? is it always the same value when the throttle is closed or does it change when the car gets hot

Yep, using Nissan DataScan program. Its the same hot and cold.

[BlackZenkiS14]

Originally Posted by cotbu

Was hoping it was a little richer. clear the ltft and stft. The ecu may have stored all that data and you might not get a change.

I'll have to look into how to do that, and try it this weekend.

[BlackZenkiS14]

I did the following test and got weird results, dont know what to make of them.

I was chasing down that 2.1V at the white wire on the TPS plug, apparently due to a system in the ECU, that should be reading 5.1V with the TPS unplugged. So I cut the wire on the back of harness about 5" away from plug to test voltage. With the wire cut, at the wire I got 1.3V sometimes, 2.4V sometimes, and 3.1V sometimes, and everywhere inbetween, at the TPS plug I got 0V (obviously). However, when I reconnected the white wires, I got 4.7V at the wire intersection, and 2.1V at the TPS plug. I have no idea what any of that means.

1.3-3.1V at wire; 0V at plug


4.7V at wire intersection, 2.1V at plug.

[cotbu]

the white signal wires voltage should go up gradually to 4.~v and stop, the wire wth 5v is the ecu reference the other is ground
you need to clear self learn.

[BlackZenkiS14]

Originally Posted by cotbu

the white signal wires voltage should go up gradually to 4.~v and stop, the wire wth 5v is the ecu reference the other is ground
you need to clear self learn.

There is a loop mode in the ECU that auto sends 5v through the white wire if the TPS is unplugged, this is the problem that I was testing, and couldnt get a conclusive answer

[cotbu]

Check the mafs voltage, plugged and unplugged see if the results are different

Sent from a Highly Tuned Note 4.5!!!

[ultimateirving]

Originally Posted by BlackZenkiS14

There is a loop mode in the ECU that auto sends 5v through the white wire if the TPS is unplugged, this is the problem that I was testing, and couldnt get a conclusive answer

Maybe a resistor failing? Causing fluctuating voltage. I'm no electrical engineer so maybe someone with more expertise can chime in. But that is odd if it should be a steady ~5v

[BlackZenkiS14]

Ok, so I unpinned the wire from the ECU harness, to completely eliminate the wiring, and at the prong on the ecu, with the wire removed, it read 4.1V, when I put everything back together, I got 4.1v at the wire, then eventually the tps plug. So that all seems normal. I also used a different ground for my meter on all these tests because I don't think the original ground I was using was clean enough.

However with all of this put back together, the car still shows the exact same problem. Totally fine when cold, but once reaching operating temp, stumbles and stutters. However, when I disconnect the white tps wire at the intersection I made, the problem goes away. It runs much smoother with the tps wire cut, and the engine does what it's supposed to.

I also then cut the wire a few inches behind the tps plug, and ran a fresh wire straight from the ecu to the tps sensor, to rule out any breaks in the wire within the harness. Did not fix anything.

There has got to be something inside the ecu that relates to tps signal that is causing this problem. It's the only thing possibly left.

[cotbu]

clear self learn

[Kingtal0n]

Originally Posted by BlackZenkiS14

There has got to be something inside the ecu that relates to tps signal that is causing this problem. It's the only thing possibly left.

When idle speed > desired idle speed, ecu will pull timing when the tps is plugged in

perhaps watch your timing at the crank when you unplug the TPS to notice if there is a marked difference

Thats about the only thing a TPS is/should be doing at idle anyways, unless its signal wire is crossed with another random wire somewhere along it's length

[BlackZenkiS14]

Originally Posted by cotbu

clear self learn

Man, I am still confused about what you are talking about. I know we've been through it, but I would love to give it a try. Can you walk me through how to do it?

I'm not familiar with this program at all yet. And I dont think that I can change or save anything on my ECU at all...right?

[cotbu]

What version do you have?

Sent from a Highly Tuned Note 4.5!!!

[BlackZenkiS14]

Originally Posted by cotbu

What version do you have?

Sent from a Highly Tuned Note 4.5!!!

The most basic version, NDS 1. It looks like I might have a button in the functions that says, Clear Self Learn?

And what exactly does that do?

[cotbu]

it clears ltft and stft it should also clear stored voltages and return data. so it would be wise to set tps to .45v, iacv to 50%, timing at 15*btdc, base idle 850rpm.and fuel pressure to 3bar. i shouldn't have assumed your engine was setup properly, but i do think you know how to do it. i would also wait till operating temp, and when you're able to drive

these aren't magical terms or really secrets, but if you look them up and its something you don't want to do, don't do it. g/l

[BlackZenkiS14]

Originally Posted by cotbu

it clears ltft and stft it should also clear stored voltages and return data. so it would be wise to set tps to .45v, iacv to 50%, timing at 15*btdc, base idle 850rpm.and fuel pressure to 3bar. i shouldn't have assumed your engine was setup properly, but i do think you know how to do it. i would also wait till operating temp, and when you're able to drive

these aren't magical terms or really secrets, but if you look them up and its something you don't want to do, don't do it. g/l

Yea, thats the exact spec my engine is set up to currently. I'll have to do some looking into and see what that will do.

Is this anything permanent or whats risk with this?

[cotbu]

No, the voltages relearning should be immediate, the long and short term trims are just that. They require new data. So if the 02sensor is working correctly everything should be fine. You could be lean or rich if the tune is on point you shouldn't have any problems. Have you ever seen a person keep getting the same code over and over even after replacing a part? it's because the ecu learns the faulty data, it will take multiple trips for the ecu to relearn as long as there is no huge fluctuations from the old data. Clearing self learn just speeds up the process, and says relearn now.

You don't want to have leaking injectors , a faulty mafs, a bad 02sensor or even fouled spark plugs
Most people see an increase in fuel economy, clearing self learn. Others will notice correct mafs voltage other will notice they can idle now at a decent rpm. If there is no change the problem is obviously still there, you just have to find it. You just might be able to see it so logging with nds is a good thing to do if you choose to clear self learn.

Sent from a Highly Tuned Note 4.5!!!

[BlackZenkiS14]

Well, fuck my life.

I just picked up an Enthalpy Tuned ECU with similar spec (same injector and maf at least), and it still does the exact same god damned thing. I'm seriously at a loss. I have no idea what to do at this point.

Is there any correlation between the ECU reading the TPS and the car warming up?

What things with temperature added could cause them to malfunction? I had ruled out actual temperature being the problem (as opposed to temperature that the ECU is reading), because it happened so perfectly with it reaching operating temp. I guess it does get worse slightly when its really hot outside compared to cool outside. But what the fucking fuck.

[jr_ss]

Have we discussed grounds on the motor? This has been going on for so long now I can't remember. Have you updated the OP?

Anyway, how many do you have? Try adding a few. 4ga wire from the block to a clean unpainted spot on the frame rail. Maybe one from the head to the bulkhead as well.

[BlackZenkiS14]

Yep, I have 3 additional engine ground on engine, 4ga. I confirmed continuity from all parts of block and head to chassis ground just last week.

Tried unplugging knock sensor, makes no difference.

[BlackZenkiS14]

Ok, did some more testing tonight.

Tested a known good knock sensor and sub harness...problem persisted.

Tested a known good set of OEM SR coil packs and sub harness, no change in problem.


I did play with the fuel pressure a little bit and paid close attention to it. When priming the fuel system (KOEO), the gauge seemed to pulse rapidly around 40-45psi. Then once the fuel pump turned off, the pressure dropped immediately to 0psi. That seems odd to me. Any ideas?

With engine running, vac line connected, its at 40psi.

Also, we increased base pressure to 65psi, and the problem seemed more prevelant and heavy. Then we dropped to 20psi base, and the problem seemed to diminish a bit, and the engine didnt seem to load up as badly. Ideas?

[daryl337]

Nevermind.

Was hoping you had top feed injectors - a pulsating fuel pressure could be indicative of a rail pulse, so a pulse dampener can help. However that should not be a temperature specific concern. Its very strange that this concern is only happening to you when the car warms up. That tells me you have either an issue on the open loop side of the tune, or possibly a voltage drop issue (however I see you have a mechanical fan so I don't think it is that) You said that the other ECU had a tune for the same injector - are you *sure* it is for that specific brand of injector? Or just similar CC's? The base injection times on the tune might be correct but if they are different brand of injectors you could very well be experiencing an issue with injector dead time.

An increase of base pressure to 65 would certainly cause a lagging issue because you are altering your injection amount significantly. I'd bring it back to proper psi so you don't add more problems. Your fuel pressure should not be fluxuating 5 lbs during priming. Does it fluxuate while running? If so, disconnect the vacuum line and test it again to see if it is fluxuating while disconnected and engine running. If it does not fluxuate anymore then you have either an issue with your vacuum diaphragm in your FPR, or you have a vacuum issue with your engine still - possibly mechanical. Your vacuum gauge in car seems fairly responsive, it should indicate a pulsing vacuum signal if that were the case. I'd think it is safe to rule out a mechanical vacuum issue, so look at that fpr.


If it still fluxuates after the vacuum line was disconnected, you gotta look into your fuel system some more. Check for leaks, check that FPR, and pump.


Best of luck to ya.

[BlackZenkiS14]

Ok, heres the update for now. Replaced my AFPR with a known good Aeromotive AFPR, and it didnt make a noticeable difference in the issue I am having, however, it did hold positive pressure after the FP turns off like it should, so I'm going to replace it anyways.

We also pulled the rail to watch injectors on fuel pump priming, dry as a bone, not a leak.

Also, I decided tonight that it is an actual temperature problem, even after the car reached OT, the problem wasnt present (weather is currently in the 50's here, so much cooler than previous testing). It took a run around the block to start hesitating like normal. So its gotta be something actually warming up, and causing malfunction.

I hooked up my NDS again to start playing with some active tests, and this time I pulled up diagnostics, and came up with Code 12 and 34...? Now, all of these tests were done on the Borrowed 62 Enthalpy ECU, not my ECU. So the o2 sensor isnt reading.

Codes...where can we trace with these? I've tried a known good MAF and a known good Knock sensor with sub harness...


Also, here is the display with engine cold, KOEO.


Here is display with Engine on, cold.


Here is display with Engine on, Warm.

[cbeuglas]

The knock should read 2.5v out and can retard timing when warm.

Sent from my SAMSUNG-SM-G920A using Tapatalk

[cbeuglas]

Also if you still have knock and MAF codes after replacing with a known good ones the check your harness.

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[BlackZenkiS14]

(also, I should note that the 34 code could have come from the testing I was doing with the knock sensor in days past, running car with unplugged, ungrounded, shielded in a rag not connected, etc...I didnt clear ECU after doing these tests)

[cbeuglas]

Clear and retest

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[ultimateirving]

You can try using a resistor, wire it in and used to fool the knock sensor, IF it keeps giving you issues.
Also I know some ecus can turn off the knock sensor input as well.

[BlackZenkiS14]

Originally Posted by ultimateirving

You can try using a resistor, wire it in and used to fool the knock sensor, IF it keeps giving you issues.
Also I know some ecus can turn off the knock sensor input as well.

Do you have a link or how-to on the info regarding the resistor in the knock sensor?

[ultimateirving]

Originally Posted by BlackZenkiS14

Do you have a link or how-to on the info regarding the resistor in the knock sensor?

I'll check around on google for you. I did it a long time again because I thought I was having issues with my knock sensor.


After a little digging around I found this.
http://zhome.com/ZCMnL/PICS/detonati...ionSensor.html
Same concept just a different Nissan.

[ultimateirving]

Originally Posted by cbeuglas

The knock should read 2.5v out and can retard timing when warm.

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I thought this number should be closer to 3.3v when reading normal.