5K breaking up, stalling, leaning out...WTF. Help

[BlackZenkiS14]

So the other day, after the car ran 100% flawless for the past 3.5 years, it finally gave me an issue.

Redtop Sr20 w/ boltons and T28@11psi. Stock injectors.

I was running the shit out of it on some backroads, just having fun, and i had a hiccup around 5k under boost. Turned it off, let it cool, and now it wont rev past 5k hardly.

It will rev fine, make boost, and power fine all the way until 5k, right at 5k it starts stuttering, stalling, breaking up, and making sounds like i'm on my rev limiter. Its not throttle or load dependent. It does this at 20% throttle and it does it at 80% and 100% throttle. No matter what, at 5K the motor goes apeshit. The Air/Fuel ratio goes very lean and becomes very very inconsistent.

I have an Emanage on it, with a good tune. I did not change ANYTHING about car, computer or tune between it working perfect 2 weeks ago, and today.

I have replaced the MAF, didnt fix anything. TPS is fine(reads a consistent accurate signal to my wideband). Injectors are all firing. ECU isnt throwing any codes. It has a newer Z32 fuel filter. New Iridium plugs (1 step colder).

Im assuming its not a spark related issue because it idles perfect, and it goes lean instead of rich.

Does anyone have any advice?

[Cloud9]

probably not the case but my brother ripped his speed sensor on a hoist the other day and ever since then the car has a werd governor at 5k rpms, once he hits 5k the car bogs down till it hits 3k then you have throttle control again. GL tho

[steve shadows]

fuel pump probably

[BlackZenkiS14]

I havent had a speed sensor on my car for 4 years. Thats not the issue. Thanks for the idea though/

I have a Walbro 255 that has been working perfect for years. Its not a boost dependent issue. Even at 15% throttle when held consistent to 5k it will cut out. Its something electrical.

[GSXRJJordan]

I'm guessing corroding grounds/loose grounds - could also be a +12v battery post getting corroded. TBH, my first guess was MAF, but if you replaced that it's gotta be a power/ground connection issue.

[steve shadows]

I havent had a speed sensor on my car for 4 years. Thats not the issue. Thanks for the idea though/

I have a Walbro 255 that has been working perfect for years. Its not a boost dependent issue. Even at 15% throttle when held consistent to 5k it will cut out. Its something electrical.

I would still physically check the fuel pump.

Walbros usually die this way, watch the fuel pressure very carefully with a gauge this is another way of checking it.

[BlackZenkiS14]

Fuel pressure at idle is 42, and rises with throttle input accordingly.

And i wouldnt think it would be the fuel pump because it only happens right at 5k, like its hitting some kind of limiter set at 5k.

But if i go to physically check the unit, what should i be looking for?

[projekt_s13]

Check your intercooler piping, mine was doing the same thing. When i hit full boost the car would sound like its hitting the rev limiter and bog out. Turns out my coupler to the throttle body was not tightened all the way so it would leak out at full boost.

[BlackZenkiS14]

Check your intercooler piping, mine was doing the same thing. When i hit full boost the car would sound like its hitting the rev limiter and bog out. Turns out my coupler to the throttle body was not tightened all the way so it would leak out at full boost.

Yea, i'd like to thinks its a boost leak, but i have brand new couplers with T-Bolt clamps. And it isnt boost dependent at all.

It hits this limiter whether im at full boost, 0psi, or still in vaccuum.

[born2boost]

mine is doing the same thing...exactly at 5k driving or free rev and it hits 16:1 and 17:1 a/f. ive replaced everything coils, ignitor, fuel pump, plugs, fuel filter. Im running a haltech, the tune was fine for 5 drift events and now its messing up. Whats your injector duty, i think that might be an issue for me. I havent changed the inejctors.

[JohnnyDrfiter22]

Why not check spark plugs it wouldnt hurt and will only take a second. For the fuel pump your going to be looking for loose or broken wiring. if you have a bad ground you might be abel to tell if bad when you turn on your stereo you hear a loud buzzing or humming. What about TPS or speed sensor i say get a multi meter on em.... GL

[born2boost]

i logged tps voltage mine with the haltec and checked with multimeter. Plugs have been pulled and checked. Im going to do some extra grounding because i have noticed my clock ilumination is flashing when the car is on and it goes away when the lights are turned on, something i havent noticed before. Im running a map sensor and the readings for the map look fine as well.

[KiLLeR2001]

I had a similar problem and it ended up being one of my coilpacks. It was fine until around 5k when it started to hesitate and no longer gained power properly. Make sure everything is grounded good also (esp the ground for coilpacks).

[born2boost]

i swapped out my coil packs and it didnt change. The ground for the coils is on the harness to the back of the head right?

[KiLLeR2001]

i swapped out my coil packs and it didnt change. The ground for the coils is on the harness to the back of the head right?

Yeah, make sure its grounded to the chassis well. If it's not the coilpacks, then it's most likely fuel related. I had a problem with one of my fuel injectors as well (tested the ohms with multimeter, i think 11.5 is the proper reading, its been so long).

[born2boost]

my head is grounded to the chassis. I dont see it being a ground if its been fine for a few races. All the grounds i can find are connected.

[BlackZenkiS14]

Born2boost, Yea, im in the same boat. I didnt change a single thing. My car ran flawless for 4 years, the last time i ever even had a wrench in the engine bay was MONTHS ago, and it ran flawless between now and then. So i dont see it being a ground. I think we are having a very very similar problem, if it isnt the exact same thing. Keep me updated on what you find.

And as far as i know, my TPS is fine. it sends the proper signal to my Piggyback, and my wideband datalogging program.

Mine is absolutely a fuel related issue. At 5k RPM the A/F ratio goes apeshit, to around 17 and 18, and sometimes up to 21. Lemme see if i can get a graph of my datalogging session up sometime later today. If it was a spark related issue, the motor would be running fat with too much fuel and not enough spark/combustion. Thats not what is happening, my A/F is going off the charts lean, and very erratic and inconsistent. Like it runs a perfectly consistent A/F all the way to 5k then goes nuts, like its hitting some kind of limiter or fuel cut etc... I need to figure out what is causing that limiter to kick in

[tckracker]

I have had a VERY similar problem with two different cars leaning out on the high end under boost or vacuum. On one the timing was advanced and it ran fine lower in the RPM even under load and boost but when I got to around 4800 rpm it would spit bog and want to die. I took a infrared temp gun to the exhaust manifold and realized my exhaust temp was WAY too high; easy fix. 2nd car it was a two part problem crappy California gas had clogged my in tank filter, the one on the end of the Walbro 255 I took it off and rinsed it in acetone to get all these little black chunks out of it( there is also a small cup filter actually in the end of the pump, cleaned that as well) and replaced my Z32 filter. The car ran better but not a complete fix, so I did some research and found that other people were having the same problem with their Walbro pump at high RPM without being dependent on load or boost. Turns out that the power the engine consumes at higher RPM was over loading the fuel pump ground?!?! I put a larger gauge wire on the ground side of the pump and grounded it to the chassis. Problem solved
GLWF
-Shaun

[BlackZenkiS14]

I have had a VERY similar problem with two different cars leaning out on the high end under boost or vacuum. On one the timing was advanced and it ran fine lower in the RPM even under load and boost but when I got to around 4800 rpm it would spit bog and want to die. I took a infrared temp gun to the exhaust manifold and realized my exhaust temp was WAY too high; easy fix. 2nd car it was a two part problem crappy California gas had clogged my in tank filter, the one on the end of the Walbro 255 I took it off and rinsed it in acetone to get all these little black chunks out of it( there is also a small cup filter actually in the end of the pump, cleaned that as well) and replaced my Z32 filter. The car ran better but not a complete fix, so I did some research and found that other people were having the same problem with their Walbro pump at high RPM without being dependent on load or boost. Turns out that the power the engine consumes at higher RPM was over loading the fuel pump ground?!?! I put a larger gauge wire on the ground side of the pump and grounded it to the chassis. Problem solved
GLWF
-Shaun

Awesome. Thank you. I am going to check my grounds on the fuel pump, and maybe put a larger ground on the FP this weekend. We'll have to see if it works.

[UNISA JECS]

I have had a VERY similar problem with two different cars leaning out on the high end under boost or vacuum. On one the timing was advanced and it ran fine lower in the RPM even under load and boost but when I got to around 4800 rpm it would spit bog and want to die. I took a infrared temp gun to the exhaust manifold and realized my exhaust temp was WAY too high; easy fix. 2nd car it was a two part problem crappy California gas had clogged my in tank filter, the one on the end of the Walbro 255 I took it off and rinsed it in acetone to get all these little black chunks out of it( there is also a small cup filter actually in the end of the pump, cleaned that as well) and replaced my Z32 filter. The car ran better but not a complete fix, so I did some research and found that other people were having the same problem with their Walbro pump at high RPM without being dependent on load or boost. Turns out that the power the engine consumes at higher RPM was over loading the fuel pump ground?!?! I put a larger gauge wire on the ground side of the pump and grounded it to the chassis. Problem solved
GLWF
-Shaun

Good info......was the high EGT's do to being to rich in teh first example?

[Rnz520]

This could be speed sensor related, if you 5th gear sensor wires go bad and ground out you will not be able to rev past 5 in any gear because it thinks you are always in 5th gear. Check those

[BlackZenkiS14]

This could be speed sensor related, if you 5th gear sensor wires go bad and ground out you will not be able to rev past 5 in any gear because it thinks you are always in 5th gear. Check those

I definately think it is sensor related. 5th gear sensor? I didnt even know about that....

hmmmm. Thats a good idea. I'll check that. Where is that located on the tranny?

Would it matter at all that i dont have the speed sensor hooked up?

[born2boost]

im running a haltech there shouldnt be a 5th gear issue. I ripped the sensor out of the car before and it was fine at an event. I will try the grounding wire.

[born2boost]

the car was fine for an hour or so and then it started breaking up again...its going in and out. Could the stock fpr be going out?

[renegade_ewok]

Check your TPS too, who knows, I've been told they can crack.

[born2boost]

tps is fine

[BlackZenkiS14]

I've heard it could be my fuel pump, which could make sense, its a 4 year old walbro 255. But i still dont know why it would run 100% rine until 5k, then right at 5k go apeshit. its gotta be some kind of sensor throwing an "Oh Shit" code to the ECU making it fuel cut.

[Oo_Skyline_oO]

thats weird, ususaly when its fuel pump related it would just have issues under load/boost. I would deffenately say fpr

[born2boost]

checked my fuel pressure today. Its not breaking up now but its super lean still. Im running a map sensor but im only getting 5 in/hg in vacume. when i pull a tube it goes right to 0 so im guessing its a small leak if one at all. I cant remember what it usually reads. Boost is being controlled fine and everything is running off of one vacuum block. I might start running the map sensor off of its own source to see if i can get a better reading.

zenki, Have you looked at your fuel pressure on the dyno? Hook up to your emanage and make sure the map is the same make sure its not corrupted. Is ecu set to change with the temperature/humidity. If you were tuned in the summer and its starting to cool down that might be where your issue is. If i think of anything else i will post up.

[jsasrsr]

im having a similar problem with my newly installed turbo.... except when i open my WG way open, the problem goes away but i get shitty boost....

but when i turn it up, i get to around 5ish k and its as if my rev limiter(which doesnt exist) is kicking in.....

i think mine is a WG problem or possibly a boost leak, but either way i fell your pain

[240sxspeed]

coolant tem sensor ok and check the wiring on the cas had the same problem b4 one of the pins on my cas was off and guess it was slighty pulling away when the motor was moving or sumthin and also i was reading a thread bout the temp sensors goin bad same symptoms try that it a 20 part u can get at autopartsstore 4 a na sr20 sentra 91 94 one more thing 255 walbros i changem every year its 80 bucks thats protects your 2000 dollar motor u know what i mean

[BlackZenkiS14]

Might not believe it, but it ended up just being my alternator. Cars runs like a facking champ now!

[GSXRJJordan]

Good to hear. So you checked the voltage and it was low, or what?