RB25 Cutting out under boost - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

xr504 · 03-03-2012, 04:10 PM

I am having some issues with my rb s14. I have a wideband and installed a AFC Neo but i could not get it tuned right under boost. When cruising around it drove fine but whenever i started building boost my afr's would drop down and bottom out at at 10 and spit sputter and cut out, also would black smoke out of the exhaust.

Then i replaced my ECU with a power fc, boost control kit, and also installed a supra tt fuel pump but i am still having the same issue

My only other engine mods are
full 3" exhaust
z32 maf
hks intake
FMIC with 3" piping
AEM wideband
Mishimoto radiator with electric fan

I am clueless as to what to do now. I have read about similar problems being boost leaks, or maf but i know the maf is good and i have not found any boost leaks. When i re wired my maf i did not use sheilded wiring, Could that cause this big of a problem? Oh also every once in awhile it will pull decent in first but then will go right back to sputtering and cutting out a second later.

Any Help would be greatly appreciated.

mantas · 03-04-2012, 12:39 AM

I had the same problem it turned out to be my turbo was blown. Does it spit smoke at idle?

91drftr · 03-04-2012, 01:37 AM

Ive dealt with a,,few rbs with same problem u should check the following:...spark plugs,coil packs,and if u have a blow off valve make sure that thing isnt opening under boost...if u have a friend with an rb thay is running good u can try his coilpacks on,ur car. I testef my coilpacks seemed like they worked fine but still had the problem then i decided to swap em out anyway and that was my problem........hope this helps

mantas · 03-04-2012, 09:17 AM

Yeah i just fixed my coils. Temp fix but it works while i want for the new ones to come in. Noticed the springs on some of the coils was loose and possibly shorter in lenght that what it needs to be. So i gently massaged the spring and got it to stretch so it reaches the top of the plug. My misfire went away, hopefully this lasts lol.

Kingtal0n · 03-04-2012, 10:56 AM

Quote:

Originally Posted by xr504

Then i replaced my ECU with a power fc, boost control kit, and also installed a supra tt fuel pump but i am still having the same issue

do you have a datalogit?
did you watch the map move when going into boost?
what happens when you try to remove fuel?

If there is a boost leak, the map will spike oddly to much higher airflow numbers than anticipated. I know the values on the load scale seem arbitrary, but there is a method to the madness. Usually there is a number like "20000" that will correspond to about 15psi of boost. If you notice the map shooting past this number, while there is only about 2-5psi of boost, and the car is going very rich, that is likely an air leak situation.

xr504 · 03-04-2012, 12:52 PM

@mantas I think my turbo is fine, it only smokes under boost when it dumps fuel. at idle it is fine, idles a little rough but not too bad.

@91drftr I replaced my plugs not long ago and made sure i gapped them correctly then rechecked them after i started having this problem. I know one other guy with a 25 so ill see if i can throw his on mine to see if thats it. And i have the factory bpv so i dont think that is the problem.

@kingtal0n I do have the datalogit kit but i have not installed it on my laptop yet due to my laptop cd drive is broke so i have not looked at the map. Since i am very new with the ecu i have not messed with anything, the guy i bought it from gave me a base tune for my mods so i havent really changed anything on it yet.

Thanks for the help.
do you guys think that it could be my maf wiring not being shielded? or should i not worry about that right now?

xr504 · 03-04-2012, 06:47 PM

Got a little more info. I was driving it today and it is getting alot worse. I noticed that when i open the throttle at all the boost gauge reads it building boost but the hand controller reads me building no boost at all, it doesnt even get out of the negative. I can bearly gain speen on the highway now because it cuts out under any throttle at all. When i was installing the boost control kit i noticed that the two wires you connect the solonoid to Is getting switched 12v to the one wire but the other that is suppose to be the ground is not getting a ground. I was told not to ground it to the body so i just connected it anyway.
Does anyone know what is going on? I am clueless

xr504 · 03-07-2012, 11:03 AM

Does anyone know why my Power fc would be reading negative boost but my boost gauge would read 10-11psi?

Kingtal0n · 03-08-2012, 05:40 PM

Your power does not actually "read boost", because it is a MAF sensor based ECU.

Where is the Boost gauge plumbed? And where is the MAF sensor?

Now, determine as boost builds up, does the Power FC show a similar increase in LOAD ? It really should pass the "10000" mark iirc just as boost builds past 0psi, but again, it depends on the situation.

Sileighty_85 · 03-08-2012, 06:51 PM

what heat range are your plugs an what are they gapped to?

username · 03-08-2012, 07:09 PM

Do you have the right hot wire in/out settings on your afc for the z32 maf?

Kingtal0n · 03-09-2012, 08:17 AM

I would recommend using a regular boost controller, and not the POWER FC boost controller. Sell that thing if you can and buy a profec B Spec-2 or a greddy type-s controller.

Sileighty_85 · 03-09-2012, 09:13 AM

Quote:

Originally Posted by Kingtal0n

I would recommend using a regular boost controller, and not the POWER FC boost controller. Sell that thing if you can and buy a profec B Spec-2 or a greddy type-s controller.

WTF Why, You cant get any better than the PFC EBC.
That has nothing to do with his issues, hes not having issues with boost spikes.

03-03-2012, 04:10 PM	#1
xr504 Join Date: Feb 2011 Location: Cincinnati Age: 30 Posts: 46 Trader Rating: (0) Feedback Score: 0 reviews	RB25 Cutting out under boost I am having some issues with my rb s14. I have a wideband and installed a AFC Neo but i could not get it tuned right under boost. When cruising around it drove fine but whenever i started building boost my afr's would drop down and bottom out at at 10 and spit sputter and cut out, also would black smoke out of the exhaust. Then i replaced my ECU with a power fc, boost control kit, and also installed a supra tt fuel pump but i am still having the same issue My only other engine mods are full 3" exhaust z32 maf hks intake FMIC with 3" piping AEM wideband Mishimoto radiator with electric fan I am clueless as to what to do now. I have read about similar problems being boost leaks, or maf but i know the maf is good and i have not found any boost leaks. When i re wired my maf i did not use sheilded wiring, Could that cause this big of a problem? Oh also every once in awhile it will pull decent in first but then will go right back to sputtering and cutting out a second later. Any Help would be greatly appreciated.

03-08-2012, 05:40 PM	#9
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Your power does not actually "read boost", because it is a MAF sensor based ECU. Where is the Boost gauge plumbed? And where is the MAF sensor? Now, determine as boost builds up, does the Power FC show a similar increase in LOAD ? It really should pass the "10000" mark iirc just as boost builds past 0psi, but again, it depends on the situation. Last edited by Kingtal0n; 03-08-2012 at 06:11 PM..

03-08-2012, 06:51 PM	#10
Sileighty_85 Post Whore! Join Date: Dec 2006 Location: Misawa, Japan Posts: 6,815 Trader Rating: (8) Feedback Score: 8 reviews	what heat range are your plugs an what are they gapped to? __________________ 後輪駆動車１番 1989 Built SR GT2871R -363whp 1998 S14 W/RB25- 250ish (For Now) 1986 SR86 - 200ish 1990 R32 GTR - 320hp Don't Buy Engines from JDM-Online http://zilvia.net/f/businesses/207457-jdm-online.html Don't Buy XS-Power or SSAC Shit

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03-04-2012, 12:39 AM	#2
mantas Zilvia Addict Join Date: Feb 2011 Location: LALALAND Posts: 822 Trader Rating: (7) Feedback Score: 7 reviews	I had the same problem it turned out to be my turbo was blown. Does it spit smoke at idle?

03-04-2012, 01:37 AM	#3
91drftr Zilvia Junkie Join Date: Oct 2006 Location: L.A 323 Age: 36 Posts: 588 Trader Rating: (15) Feedback Score: 15 reviews	Ive dealt with a,,few rbs with same problem u should check the following:...spark plugs,coil packs,and if u have a blow off valve make sure that thing isnt opening under boost...if u have a friend with an rb thay is running good u can try his coilpacks on,ur car. I testef my coilpacks seemed like they worked fine but still had the problem then i decided to swap em out anyway and that was my problem........hope this helps

03-04-2012, 09:17 AM	#4
mantas Zilvia Addict Join Date: Feb 2011 Location: LALALAND Posts: 822 Trader Rating: (7) Feedback Score: 7 reviews	Yeah i just fixed my coils. Temp fix but it works while i want for the new ones to come in. Noticed the springs on some of the coils was loose and possibly shorter in lenght that what it needs to be. So i gently massaged the spring and got it to stretch so it reaches the top of the plug. My misfire went away, hopefully this lasts lol.

03-04-2012, 12:52 PM	#6
xr504 Join Date: Feb 2011 Location: Cincinnati Age: 30 Posts: 46 Trader Rating: (0) Feedback Score: 0 reviews	@mantas I think my turbo is fine, it only smokes under boost when it dumps fuel. at idle it is fine, idles a little rough but not too bad. @91drftr I replaced my plugs not long ago and made sure i gapped them correctly then rechecked them after i started having this problem. I know one other guy with a 25 so ill see if i can throw his on mine to see if thats it. And i have the factory bpv so i dont think that is the problem. @kingtal0n I do have the datalogit kit but i have not installed it on my laptop yet due to my laptop cd drive is broke so i have not looked at the map. Since i am very new with the ecu i have not messed with anything, the guy i bought it from gave me a base tune for my mods so i havent really changed anything on it yet. Thanks for the help. do you guys think that it could be my maf wiring not being shielded? or should i not worry about that right now?

03-04-2012, 06:47 PM	#7
xr504 Join Date: Feb 2011 Location: Cincinnati Age: 30 Posts: 46 Trader Rating: (0) Feedback Score: 0 reviews	Got a little more info. I was driving it today and it is getting alot worse. I noticed that when i open the throttle at all the boost gauge reads it building boost but the hand controller reads me building no boost at all, it doesnt even get out of the negative. I can bearly gain speen on the highway now because it cuts out under any throttle at all. When i was installing the boost control kit i noticed that the two wires you connect the solonoid to Is getting switched 12v to the one wire but the other that is suppose to be the ground is not getting a ground. I was told not to ground it to the body so i just connected it anyway. Does anyone know what is going on? I am clueless

03-07-2012, 11:03 AM	#8
xr504 Join Date: Feb 2011 Location: Cincinnati Age: 30 Posts: 46 Trader Rating: (0) Feedback Score: 0 reviews	Does anyone know why my Power fc would be reading negative boost but my boost gauge would read 10-11psi?

03-08-2012, 07:09 PM	#11
username Zilvia Member Join Date: Sep 2008 Location: Florida Age: 31 Posts: 207 Trader Rating: (5) Feedback Score: 5 reviews	Do you have the right hot wire in/out settings on your afc for the z32 maf?

03-09-2012, 08:17 AM	#12
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	I would recommend using a regular boost controller, and not the POWER FC boost controller. Sell that thing if you can and buy a profec B Spec-2 or a greddy type-s controller.