rb25det sputtering past 10psi. hard to start. read tons of threads! need rb guru help.

[LJBS14]

I have spent months troubleshooting this problem and I've ran out of ideas.
R33 rb25det series 2 swapped into s13.
Rundown of problem:
The car has always had a problem starting when it was hot. Installed brand new coolant temp sensor. Made no difference. Flash forward i did a recent turbo upgrade. Garrett Gt3071r. Deatchwerks 550cc injectors. Tial external wg. And a rs enthalpy rom tune using z32 ecu. I drove the car around and even did a drift event at around 10psi. Everything felt awesome except for when i would try to restart the car after driving it, it will not start it will just crank until the battery dies. Now if i push start it, it will fire right up very easily every time. The other problem is when i throw on my mbc and turn the boost up to 14 psi the motor breaks up past 10 psi. The rpms will continue to rise if i stay on it, it will just keep sputtering but holds the 14psi according to my boost gauge. The most logical thing i can think of is some sort of fuel cut. Im unsure if there is a correlation between these 2 problems.
MOD LIST: full 3 inch turbo back exhaust. Intake. Isis freddy intake manifold. Cx racing fmic. Other than that and the turbo and fuel upgrades mentioned the motor is stock. I also used a brand new wiring specialties plug and play harness.
Troubleshooting i have done:
-I started small first made sure the fuel pump is priming. I looped the fuel pump relay bypassing it to verify the relay is not faulty.
-CAS i did the manual check by removing this spinning it and verifying the injectors clicked. I didnt check spark but i did remove the coilpacks and checked for cracks or any damage and they are still in great shape. The spark plugs are faily new only 5k miles i pulled em anyways and they look great no abnormalities, normal wear. Proper gap
-BOOST LEAKS. I fixed every tiny boost leak i could find. I pressurized the system from the intake to at least 12psi and everything checks out. The shaft seals on my q45 tb were massively leaking. I fixed it hoping it was the source of trouble and no relief same symptoms.
-IACV / ACC. I replaced iacv with a brand new one no difference, lines to both sensors are fine no leaks.
-FUEL PUMP. Installed a brand new walbro 255. No change.
The idle is perfect the car drive absolutely normal until i go wot and hit past 10psi. Now if i do a pull at around 75 pecent throttle the boost will go past 10 psi and the rpm will climb all the way to redline with no sputter but as soon as i push a little more to wide open throttle it immediately sputters. Also sometimes i will go to start the car and it will fire right up. Ill turn it off and try to start it again and it will just crank.
-Im hoping someone can give me a little guidance on what to do next to fix these 2 issues or share if they have had similar issues and what has worked. I feel like i have read every thread out there any help is appreciated.

[xracerx972]

Did you do a proper base timing setting after you moved the CAS?

Hot start issues tend to be tune related. Its possible youre maxing out your MAF sensor with the boost sputtering, but theres a good chance thats tune related as well

What AFR are you seeing when its breaking up?

Are your injectors size and deadtimes properly set?

Is your alternator giving proper voltage while running?

Are you getting spark leak from your stock ignition coils?

[LJBS14]

Waiting on my wideband so i can check afr.
I marked the CAS before removal and installed it back in the same exact location.
Rs enthalpy tuned the ecu for the correct injector and correct size so the deadtimes should be properly set.
Ill start with the afr check at break up. Ill also do the alternator voltage and check out the coils properly to start and post my results.
Thanks for the reply.

[Yellow4g63]

Break out the timing light and check it again. Also did you wire the ecu up right? there is a wire that comes from a sub harness under the dash in the S13 that's supposed to be wired to the ecu to let it know the car is on and ready to start.

[xracerx972]

+1 its possible the base timing was already off before you even touched it..

Im willing to bet its ignition related, the breakup part anyways..

[LJBS14]

So checked the timing today it was spot on 15 degrees. Still waiting on wideband but next will be to check coilpacks for leakage. I'm also going to take a video tomarrow and post to give a clearer look into it.
As far as the maf maxing out i thought stock rb25 mafs could handle at least 350hp with a proper tune? I believe the subharness you are referring to is hooked up properly i remember plugging in a connector or 2 under the passenger side dash to the plug and play harness.
And just another thing to note that ive been noticing if i tap the throttle a few times as i crank, it fires up the 1st time, hesitantly. if i dont tap the throttle it will just crank. I dont understand how this works being the car is obviously fuel injected and i thought this was just a trick for carb'd vehicles.

[Yellow4g63]

pin #43 on your harness needs to be hooked up to the subharness on the S13. Same goes for the RB20's. When it's not hooked up the car will just crank ang crank and if you put your foot into it the car will start. Mine did this till I hooked up the pin.

[xracerx972]

As far as the maf maxing out i thought stock rb25 mafs could handle at least 350hp with a proper tune? .

You may be right, Im probably thinking of the stock turbo not being good for much..

Im still a little weary about this tune though. I dont believe too much in off the shelf kind of tunes that are supposed to work on whatever, like this is what i have on this engine and boom heres your file to upload and youre done.. It may be a good starting point, but you wont know til you get the car up to temperature and give it WOT with your wideband hooked up.

If everything mechanical checks out and theres no boost cut features in the ecu, the only variable left is the tune.. Post back with the AFR you see at full boost, or when it starts breaking up.. If its lean, you have fuel supply issues, if its rich, it could be too much fuel or not enough spark..

Also, check a spark plugs porcelain for black specs or for diamond looking shiny specs just for safe measure.. Thats a good way to see if youre engines knocking itself to death.. Hope this helps.m

[LJBS14]

Thanks for the advice xracerx972
So i finally got my wideband installed and got some time to drive the car around to see what's going on. Btw wideband is a brand new aem uego. Cruising around afr's look normal staying around 14.3-15. Idle after being fully warm is around 15.7 and higher, its jumping up to 17 then back down to 16 and 15 quickly and after a little investigation i have a tiny exhaust leak at the turbo to elbow connection at the gasket and from what i read this could possibly throw off the reading at idle to look lean at idle. Definitely plan on fixing this when i get some time.
Now for the big mystery, at wot the afr's dip down to 10. Thats the lowest reading the gauge reads so im sure its even richer than that. I took off the mbc and ran stock boost for the testing. Anything past around half throttle made the afrs go straight to 10. I did a run with the mbc to see what it was at breakup and i didnt see a change in reading from 10, i didnt want to damage the motor so i tryed to not test the breakup more than i needed.
Will this tiny exhaust leak cause me to have a faulty reading at wot? I have read that it shouldn't matter because its under pressure and not drawing in fresh air so the sensor should get a proper reading. Sensor is installed about 14 inches downstream of turbo by the way.
What could cause me to see afr's this low at wot? I dont want to blame the tune right off the bat, martin at rs enthalpy has a great reputation for his tunes and i want to rule out all mechanical issues before contacting him.
As far as the coilpacks go if they were faulty wouldnt i be able to physically see cracks on them? Do they have the potential to cause the motor to run this rich?

[Ty P]

After reading this entire thread I am seeing the exact same problems with my RB20 rom tune, different turbo, stock maf, 555 injectors, leaks fixed, all sensors replaced, cruising afrs and driveability is good but anything north of 4000 rpm and 7 psi of boost it sputters bad and afrs strait to 10.0. I even replaced the ignition setup with a waste spark setup and it made no difference with the sputtering.

this is a screen capture of the datalog zoomed in to the couple of seconds ware the sputtering was the worst at wot.

[xracerx972]

Sorry for the delayed response. 10 flat is way too rich really. You want to target like 10.9 on the safe side and maybe 11.2 or 11.3 on the aggressive side for 93 pump gas. You didn't mention if you have a FPR set for the proper fuel pressure, but it shouldn't be that big of a deal as the tune could be adjusted for the higher than normal pressure. There's really no great way of testing coilpacks with every day kind of tools, but faulty coils could definitely cause the mixture to not be burned properly.
As for the leak, as far as Ive read, people generally agree that an exhaust leak can cause the AFR to show leaner than actual, but certainly not richer than actual. So your idle numbers sound decent (assuming theyre showing leaner than it actually is), but the WOT is definitely way too rich.

"Now if i do a pull at around 75 pecent throttle the boost will go past 10 psi and the rpm will climb all the way to redline with no sputter but as soon as i push a little more to wide open throttle it immediately sputters." - The only differences here is airflow volume and throttle position (load) meaning your tune is accessing different areas of the map where at 75% part of the map may be decent, but the 100% load and airflow is too rich. Im inclined to believe that if your coils were faulty, they would still misfire at 6500rpm regardless of load. -Someone correct me if Im wrong..

I have a set of splitfires that I dont need if youre interested in testing them out to eliminate the coil variable. I could sell them to you for 150$ or so and if that doesnt fix your problem, you can send them back and Ill refund your money. They worked fine for me, but I use LS coils now.

There is one last thing thats a little difficult to diagnose and thats knock. Its very possible that excessive knock will cause your ecu to retard the timing, hence the reason for checking the porcelain on your plugs for black specks. Im still really leaning towards that tune being too rich.. If there is no excessive knock, the only damage thats possible from running too rich is gas-washing the bores which can wear out your rings. When your dipstick starts really smelling like gas, then youre really risking wearing out your main bearings and if left unfixed for long enough, your internals will eventually fail prematurely.

[Ty P]

with that being said is there any reason that it would sputter at the same rpm regardless of load like in neutral free revving or in gear driving. Could neutral switch inputs or speed inputs to the computer have any affect on this issue?

[Yellow4g63]

Almost sounds like boost leak

[xracerx972]

Transmission sensors play no role in what area of the map is being referenced.

It is always a good idea to check the alternator output voltage, as that only takes 5 minutes. You can then rule out a faulty alternator not giving enough voltage to the engine components. The rb20 is a bit different from the series 2 rb25 as far as wiring. Always ensure the base timing is properly set, and you have good plugs with the proper gap. Ensure the engine and components are properly grounded. If you have a really rich or lean tune, fix that next. if you still have problems after the tune is good, then I would suggest coils. You can see if your coils are arcing at night, you may see the sparks grounding out on the engine.. Just some suggestions.

And +1 on what 4g63 said, you should boost leak test your car if you havent already.

[LJBS14]

Thanks for all the knowledge. Im crossing fingers on the coilpacks being faulty, I've been seeing a trend on threads of them not holding up when people upgrade their turbo systems and/or up the boost. I'm trying the cheapest method first of insulating them. Depending on what happens i might take you up on that offer for the splitfires.

[LJBS14]

xracerx972 im ready to paypal you for those coil packs if you still got them. Insulating my stock coils did nothing for me.

[LJBS14]

xracerx972 i got your pm but i cant reply, i guess i dont have enough posts. Text me at 951 378 2841 or email @ [email protected] if you can so i can communicate with you. Thanks

[Yellow4g63]

Riverside? or Moreno Valley? LJBS14?

[LJBS14]

Moreno Valley yellow4g63

[Yellow4g63]

want to borrow my stock coils to check? I'm on LS2 coils now. Mine fit S1 RB25 so unless they are different you can test with those.

[LJBS14]

I would of love to, but im pretty sure the s1 coils are different being that they require an igniter unlike the series 2. Thank you for offering tho i do appreciate it, xracerx972 is shipping out the splitfires tomarrow so im hoping that will help me out.

[Yellow4g63]

I'm in Moreno Valley by RCC. If you want just meet me tomorrow after 6. I should be home from work around that time.

[Yellow4g63]

my number is 951 235 5184

[LJBS14]

Update: installed splitfires, got a retune to lean out the wot afr's. Afr's now look great, at wot its showing around 10.8-11 range. Sadly the problem still persists with increased boost. I set the boost to 12psi and it sputtered a bit i noticed it sputters harder with higher levels of boost i had it at 15 psi and it was a more severe sputter than it was at 11-12 psi. Another thing i noticed with this retune, i held the sputter at wot all the way through 2nd gear and the afr's actually leaned out to high 12s to low 13 bouncing around in that range when i was at full boost and wot.

[xracerx972]

That sounds a little too lean.. Anything above 11.3 at WOT is too lean for 93. Was this a dyno tune or an ecu reflash?

Timing is absolutely critical in boost.. Is there any way you can post up pictures of your fuel or timing tables?

[LJBS14]

Problem solved!
I'm pretty upset with myself for overlooking the small things.
basically I was getting spark blow out. after reading a few more threads this past weekend something stood out to me regarding spark plugs. basically I was running bcpr6es-11, I was unaware that the -11 meant these were pre gapped to 1.1mm. when I went to check the gap a few months back I didn't fully understand that .8 meant .8mm and I was using the gap tool improperly to measure. I wrote it off the list without educating myself how to properly gap a spark plug
anyway I threw in some ngk bcpr7es pre gapped to .8mm (i double checked all 6) and took it for a spin, and bam! 17psi all the way to redline; strong with no sputter. I'm glad I finally got the issue resolved and I definitely learned a lot about troubleshooting this issue.
Thank you to everyone that helped out! I am very happy to finally be able to floor it again