SR Stutter and miss when engine is warm?

[BlackZenkiS14]

Originally Posted by cotbu

So what did the jwt techs say?
Did they at least send you a new tune to test out?

Yea, they did, they sent a new tune to install, and it didn't really make a difference, car runs a bit better I guess, but didn't change this issue at all. :/

From all the logs I've sent them, they really weren't able to identify any problems in the setup at all...

[cotbu]

So really there's nothing wrong and you're so ashamed that your 240 runs perfect and makes good power, when everyone else's runs like crap, You just want to fit in somewhere ,but the you're doing it wrong! thread won't except you! Oh what to do!
J/k

But seriously, it must be something simple, I'm sure you'll get it sorted out! G/l

Sent from a Highly Tuned Note 4.5!!!

[spooled240]

Could it be possible that you have an intermittent head gasket leak that's fouling out the plugs? When the car is fully warmed up and the coolant system is pressurized it might start leaking into the combustion chamber.

[Kingtal0n]

i Hope I said it already (didnt check) but I suggest going back 100% oem and start from there.

[BlackZenkiS14]

Originally Posted by spooled240

Could it be possible that you have an intermittent head gasket leak that's fouling out the plugs? When the car is fully warmed up and the coolant system is pressurized it might start leaking into the combustion chamber.

Nah, a head gasket leak wouldnt make 420whp on pump gas

[ultimateirving]

Your plugs are bkr7e, copper I presume? Have you tried iridium or platinum ? I couldn't get my ls coil packs to fire correctly with coppers. But she ran beautifully when I switched(gotta double check if it is platinum or iridium in there now.)

[BlackZenkiS14]

Originally Posted by ultimateirving

Your plugs are bkr7e, copper I presume? Have you tried iridium or platinum ? I couldn't get my ls coil packs to fire correctly with coppers. But she ran beautifully when I switched(gotta double check if it is platinum or iridium in there now.)

I ran coppers for last season, but switched to the old trusty BKR7EIX Iridiums this year. Same exact issue.

[KiLLeR2001]

Have you checked voltage and resistance on the TPS sensor when it has warmed up? I've had issues before with a TPS that, once hot it would have dead spots along the range that would cause hesitation like this. So what I would do first is test resistance by unplugging the tps sensor and probing the appropriate terminals and slowly open the throttle chamber to see if the numbers climb up / down in a linear pattern.

Resistance range is 2 kOhm closed throttle to 10 kOhm WOT.

[cotbu]

Originally Posted by KiLLeR2001

Have you checked voltage and resistance on the TPS sensor when it has warmed up? I've had issues before with a TPS that, once hot it would have dead spots along the range that would cause hesitation like this. So what I would do first is test resistance by unplugging the tps sensor and probing the appropriate terminals and slowly open the throttle chamber to see if the numbers climb up / down in a linear pattern.

Resistance range is 2 kOhm closed throttle to 10 kOhm WOT.

I already suggested testing the tps, it should have given the same results, if it was failing as a lazy throttle response. Assuming he already ruled it out as that was a year ago.

Sent from a Highly Tuned Note 4.5!!!

[Kingtal0n]

The car should run pretty normal without a tps connected.

Nay a misfire. You have to think about what it means. Engine only wants 3 things; spark fuel compression. universal.

So #1 is compression test. You are sure the squeeze is there etc... Then move on to #2

Fuel. Your wideband shows good numbers, fuel pressure is there, etc... then move on to #3


SPARK. To have fuel and compression without spark occasionally, is to occasionally have a misfire. Anything from the computer to the spark plug is responsible. If you have a wiring specialty harness I strongly recommend you investigate the ECU plug, because I had a recent ignition misfire on an sr20 using their harness, and it turned out to be the ECU plug pin for a coilpack signal wasnt making a full contact, all the time.

In any case, if you cared enough you could go back to stock everything and see if the problem persist. That would narrow it down quite a bit, whether the problem did or did not still persist would provide valuable insight. A misfire is elusive, it could be a valve popping/hanging open because of a weak spring once in a while.

[cotbu]

go disconnect the tps from your sr20det, start it, oh normal now try to drive! if you don't notice a change your tps was faulty or not working. an engine running and operating are two different things.

I don't think going back to stock is an option, but if he has to by all stock sensors and harness he should just troubleshoot as much as he can before buying stock stuff.

[BlackZenkiS14]

I actually plan on trying a whole new known good TPS sensor. I know that the voltage coming out of it is correct, I've verified at the sensor, and with my Nissan Data Scan program.

[daryl337]

Does this stumble occur just after hitting the accelerator or does it continue the misfire up into the rpms afterward? Your throttle blips in vid appear to be about 500-1000 rpms worth, however if you hold this throttle does it continue to misfire as you go higher?

If it doesn't (meaning only stumbles on the initial blip) I think your throttle enrichment settings may be off on your tune.

Once the engine warms up and goes into closed loop I wonder if there is a separate throttle enrichment map on the ECU. I don't know enough about the ECU's and ROMS to say definitively - since all of my tuning is done on standalone systems.

But I really think it sounds like you are having a momentary leaning moment. You won't reflect this on a dyno or anything- because its only in effect when you first blip the throttle plate open.


Just my 2 cents.

[BlackZenkiS14]

To be honest man, I agree completely. Unfortunately I have a hard time getting ahold of JWT to have them go through the logs and tune.

Thanks for the input man!

[BlackZenkiS14]

Ok, new update:

Was having the trouble really bad today, figured out that when I unplug the TPS, it revs perfectly fine, however, with the TPS plugged in, it starts stumbling and stuttering again.

Gonna try to locate a a new known-good TPS next week to try.

[KoukiMonsta]

Originally Posted by BlackZenkiS14

Ok, new update:

Was having the trouble really bad today, figured out that when I unplug the TPS, it revs perfectly fine, however, with the TPS plugged in, it starts stumbling and stuttering again.

Gonna try to locate a a new known-good TPS next week to try.

Man I hope this is the ticket.

It's been a while...without reading original posts I am assuming your TPS voltage checked out? (0.45-4.0v)?

That can be the trouble with these sensors..work fine without load but introduce heat, voltage drop, high rpms..blah blah and things can get funky.

again, fingers crossed!

[BlackZenkiS14]

Originally Posted by KoukiMonsta

Man I hope this is the ticket.

It's been a while...without reading original posts I am assuming your TPS voltage checked out? (0.45-4.0v)?

That can be the trouble with these sensors..work fine without load but introduce heat, voltage drop, high rpms..blah blah and things can get funky.

again, fingers crossed!

Yep, that's why I wrote it off so early. I voltage tested it, and datalogged it very early in the process, so I never went back to it. Really hoping this clears it up!

[BlackZenkiS14]

FUCK, FUCK, FUCK. Seriously.

Ok, replaced TPS with brand new OEM ($90) TPS sensor. Resting voltage is .44V, WOT is 4.02V, has smooth steady voltage curve as throttle increases....SAME EXACT FUCKING PROBLEM. No difference at all.

However, with the TPS unplugged, it runs much smoother, way better.

Plugged in the NissanDataScan ConsultPort to watch voltage, noticed that the voltage displayed when TPS is unplugged is 5.1V. Car revs much smoother. IDK WTF!!

Any help from here?

[inopsey]

what wiring harness are you using? oem or wiring specialties

[KiLLeR2001]

Make sure you are doing your tests when the car is fully cool and when its fully warmed up. See how the numbers fluctuate when its plugged in and when its not plugged in.

So you'll have 4 tests to conduct:

Test 1: Cool plugged in values (voltage).
Test 2: Cool not plugged in values (resistance).
Test 3: Warmed up plugged in values (voltage).
Test 4: Warmed up not plugged in values (resistance).

For values, with harness plugged in to the TPS sensor, 1. fully closed voltage and 2. WOT voltage. With harness unplugged from TPS sensor, check 1. resistance in kOhms fully closed throttle and 2. resistance in kOhms in WOT. Also be sure to check the curve all the way through the range on all 4 tests.

Report back.

[BlackZenkiS14]

Originally Posted by inopsey

what wiring harness are you using? oem or wiring specialties

OEM, and the harness has been fine in the past for 3 years of driving, then I rebuilt engine and this problem developed.

[cotbu]

Originally Posted by BlackZenkiS14

FUCK, FUCK, FUCK. Seriously.

Ok, replaced TPS with brand new OEM ($90) TPS sensor. Resting voltage is .44V, WOT is 4.02V, has smooth steady voltage curve as throttle increases....SAME EXACT FUCKING PROBLEM. No difference at all.

However, with the TPS unplugged, it runs much smoother, way better.

Plugged in the NissanDataScan ConsultPort to watch voltage, noticed that the voltage displayed when TPS is unplugged is 5.1V. Car revs much smoother. IDK WTF!!

Any help from here?

The voltage with tps unplugged is normal and says to the ecu you are at full throttle, this leads me to believe you have a fuel delivery problem and maybe timing. Does the wideband read richer with the tps unplugged?
With the throttle(pedal) all you really control is air flow the ecu controls the rest. Try clearing ltft and stft.
ps $90 for a tps is rape!

[BlackZenkiS14]

Originally Posted by cotbu

Try clearing ltft and stft.

What does this mean?

And yea, it was $75+shipping.

I'm going to test continuity tonight with the wires and make sure the plug is functioning normally.

[BlackZenkiS14]

Checked wiring at TPS plug:

Here is what I get:

Black= continuity with ground, no voltage
White= 1.8-2.1V, no continuity with ground
Red/Green = 5.1-5.2V, no continuity with ground

[cotbu]

LTFT and STFT long term and short term fuel trims. you can clear them with nds, and nistune.
Those values look good for tps disconnected, iirc. I think its something else.
wide band reading?

[BlackZenkiS14]

Originally Posted by cotbu

LTFT and STFT long term and short term fuel trims. you can clear them with nds, and nistune.
Those values look good for tps disconnected, iirc. I think its something else.
wide band reading?

How do I clear those with NDS? I've only used that program a bit, and only a for data watching and a few of the active tests.

I'll report back with wideband info tomorrow, just idling with plugged in and unplugged?

What about my 2.1V at the plug without being plugged into TPS? Shouldnt the white wire show 0v? as its just the signal return wire?

[cotbu]

clear self learn, i use to have sequence for nds, clear self learn the set or check base idle and timing.
The voltage is correct, and i may have said its wide open throttle, but its actually part or half throttle with tps disconnected, that why i think its fuel and or timing because you said it runs much smoother, way better.

[BlackZenkiS14]

AFR is 14.7-15.1 at idle, with or without the TPS plugged in. No Change.

[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.

[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