RB25DET Sputtering under boost (WOT)

[jetpower]

I have a series 2 in the s13. It's completely stock except for a few basic mods: godspeed FMIC kit, spec clutch disc, full 3 in exhaust (no cat), and walbro fuel pump. I put a manual boost controller that I got from ebay for $12 and set the boost to 10psi. It pulls hard sometimes and sometimes it doesn't. Tonight for instance, I down shifted to 3rd going 60mph on the highway to feel the pull, when it hit 6k rmp it started to back fire and sputtering then after that, it did not pull whatsoever. When I got home, I popped the hood and saw a glowing red turbo and the exhaust manifold. I am guessing it's running lean...:ugh: I know for a fact that it's got a dirty airfilter but i don't think it has anything to do with it. There is no vacuum leak or boost leak. It has the sparks plugs (platinum) for 300zx tt. I am going to check the gaps on them tomorrow, change the fuel filter as well as the airfilter. If neither works then I am going to have to look at the timing. Any suggestions will be appreciated.

[cotbu]

Sounds like you detonated and timing was retarded, just and opinion or guess.
check timing first.

[rc1honda]

Sounds like you detonated and timing was retarded, just and opinion or guess.
check timing first.

Yeah i agree with this, maybe your had a boost spike and ecu went into limp mode. Second thing I was going to say was your plug gaps. Sounds like the might be way to large.

[sidewayz240]

x3 on changing the plugs and setting the gap correctly, If that dosnt work theres a good chance you coil packs are on their way out, grab some splitfires.

[jetpower]

So I gapped them to .25 and took off the boost controller but still no luck. I am going to check the timing right now.

[Neejay]

hmm

Does it do like this:
(skips at 0:13 and 0:15)

YouTube - s13 RB25DET dyno (http://www.youtube.com/watch?v=0bzLSEK7fPo)

[!!chuy!!]

another coilpack issue...thats for dam sure!!!!!

[jetpower]

Neejay, no it doesn't skip like that. It just runs like crap at WOT, full boost (7psi). I can hear the engine screaming wanting to go but it's not going anywhere, the RMP is not rising like it's supposed to.

I think Chuy is right, I am in process of insulating the coilpacks at the moment hoping that it's not too late. A bottle of liquid tape for $5 at walmart, not bad. Well, It's 4am in the morning here in TX but thank god we're still off for the break. I am going to put this puzzle together and let yall know the result. By the way, one of the nuts on the turbo exhaust housing was loose, could it be the culprit?

http://i448.photobucket.com/albums/qq208/silver236936/IMG_0252.jpg

http://i448.photobucket.com/albums/qq208/silver236936/IMG_0255.jpg

http://i448.photobucket.com/albums/qq208/silver236936/IMG_0254.jpg

http://i448.photobucket.com/albums/qq208/silver236936/IMG_0253.jpg

And my friend's lovely pitbull.
http://i448.photobucket.com/albums/qq208/silver236936/IMG_0237.jpg

[CursedGTR]

Did you check all of the couplers for your piping? Make sure you have no major air leaks in that system. I used to have a similar problem and it turned out to be a smallfracture in a coupler that only opened up under boost. You have to physically remove and check each one sometimes in order to find it if this is the case.

Clean out your MAF, seen RB25 and Rb20's sputter alot and act like they your description when MAF's go bad or get too dirty.

Everything else I can think has been covered.

[jetpower]

I just checked the couplers right now and didn't find any holes.

So I just took it for a little spin and still no luck. sigh, does anybody have any spare coilpacks that I can use to test? I am really thinking it's the coilpacks.

[steve shadows]

make sure each coil pack is actually touching the tip of each plug, and like the previous poster, insulate and make sure they are not losing spark before getting to the plug somehow. Make sure the plugs have the end tips that work with JDM cars, some of the plus in us have shorter reach and dont make good contact with the inside of the coil packs, as they were dsigned with OEM in mind, with distributors in many plug situations...happens with RB and VG plugs a lot. Make sure the grounds for the coil pack system are also good and all the wiring is in great shape, 90% of quirky issues on these damn cars with basically stock swap setups is crap wiring from crap motorsets to begin with....

[jetpower]

steveshadows, thanks for your advice. I just got some LS2 coilpacks from some guy off of craigslist for $150 for all 8 (off of a 2006 silverado) but still NO LUCK!!! I wired up everything correctly, properly soldered, and insulated. My dad did helped me out too since he's an electrician so I can assure that the wiring is done right. After driving the car for about 20mins, I popped the hood in the dark and saw the plug wires arcing to the head and also saw #5 and #6 coilpacks with minimal arcing inside. So I thought the plug wires were bad so I went ahead and dropped $40 for Accel plug wires but still nothing, instead, it feels like redlining a gsxr or cbr around 4k+ rmp (yes, harcore sputter). Sometimes when I slowly rolled on the throttle, it climbed through the rmp fine and made power but it was not consistent. I am tired of all this, it all happened when I decided to put on that stupid boost controller which was set to only 10psi!! It ran fine for a day or two then it started to lose power at high rmps.:wtf: At this point, I really want my beastly RB back.

I am running out of solutions but obviously the wire plugs or coilpacks are not supposed to be arcing even if they're hard to notice. When I installed the LS2 coils, I did a sloppy job at the end; I just connected the plug wires to the coilpacks and that was it, yes, I did not mount them to anything, I just had them set on the head, and now after purchasing the Accel plug wires they're sitting on at the side where power steering is. My question is, do the coilpacks themselves need to be grounded even though it has two ground wires (one for the original harness ground and one for the chassis ground)?? Also, can the plug wires touch anything like the head or even each other? Any help will be appreciated. I will take a pic of my shameful work tomorrow.:bash:
I really don't think it's a timing issue...

[jetpower]

bump, does anyone know how to solve this issue?? I gapped the spark plug down to .27 and made brackets for the LS2 ignitors. It ran like a beast for about 20 mins then it started to lose power when boosting. What the heck is wrong with it????? By the way, sputtering is gone.

[handinpants]

All this, cause you took an ebay shortcut, next time wait til you have enough to,buy injectors and a,digi boost controller, i didnt want the headache so i waited

[jetpower]

Checked the timing and it was dead on....any ideas?? It seems to lose power at higher rpm (4k+) at WOT after driving it for about 20mins. Any help will be greatly appreciated.

[badboy6686]

Do a proper boost leak test, not just a visual inspection of the couplers. You're either loosing spark which you seem to have remedied or you're loosing air through a boost leak.

[96Turbo]

pull your ecu codes. faulty knock sensor wiring will cause it to retard timing. that will kill power, and make your exhaust system super hot.

[jetpower]

alright, I will look for the leak with a proper method. If there is a boost leak, then won't it won't you noticed right away? By the way, my electric fan is on at all times and i have only seen it once rise to the optimal temperature in traffic. Could this be the issue? I know the coolant temp sensor tells the ECU to run rich when the engine warming up.

[jetpower]

still losing power after 4k rpm. it's not pulling like it's supposed to.

[smelly240]

what maf is on the car? stock?

you can hook a 1 megaohm resistor to each knock sensor wire and run it to ground to eliminate them as the issue. This will simulate a no knock situation.

I think you need to do an actual boost leak test.

[S14lover702]

check the bolts on the turbo compressor housing i had a similar issue on my rb25 one of the bolts came out would run fine till under boost would show that it was building the correct amount engine was reving but same thing not going anywhere i beleive there are 5-7 bolts that hold the housings to the bearing cartridge hope this helps good luck and CHECK KNOCK SENSOR PLUGS i had a broke one and it would fall off every once in awhile woould do same type of issue

[MR.RMSCHIKO]

fuel pump or MAF imo

[jetpower]

thanks for yall's inputs. I'm taking it to a shop tomorrow for a diagnostic.
For now, I am going to check all the exhaust bolts make sure there is no leak.
Will the knock sensor cause to run like crap after engine is warmed up?
I am running a stock MAF.

[conrad_s13.5]

my friend has a very similar problem,...was this ever figured out?

[240jake]

yeah im having this problem on an sr20det. interested in a solution, ive replaced coils and igniter as well as fuel pump.

[240jake]

So i fixed this problem on my sr20det s14 by going to autozone and buying maf cleaner. After i sprayed it out she purred like she should again. Hard to believe just a dirty mafs could cause so much power loss and problems. So spend 6 bucks and try that first for anyone thats having this issue.

[RB240zDET]

So i fixed this problem on my sr20det s14 by going to autozone and buying maf cleaner. After i sprayed it out she purred like she should again. Hard to believe just a dirty mafs could cause so much power loss and problems. So spend 6 bucks and try that first for anyone thats having this issue.

With all nissans one of the first things I ever check or tell friends to check is the MAF, a bad or dirty MAF can cause the entire car to run like crap. Also clean and check the MAF connector as well, seeing as they like to get corroded all the time. As to the RB20 problem with the coil packs this is why I switched to a MSD ignition module. Never had a spark problem after that.

[SkylineHatch]

im having the same issue, I just replaced my 02 sensor this morning because it was lazy and wud read dead lean no matter what, now it runs way better and has sum of it power back but its still slow and spits under load WOT around 4k and up, ima start out by replacing my plugs because I ran shitty fuel additives n now all my plugs look brown n crappy so hopefully the new 02 n fresh plugs solve my issue, but could it possibly be the coil packs? cuz it gets way worse ass I add fuel to the point of no horse power at all and the motor spitting so bad it wont move past 5k but im not blowing black smoke

[SkylineHatch]

I also have a brand new MAF, New top mount turbo, greddy intake greddy e manage piggy back, 3 inch turbo exhaust, plugs gapped to oem spec, new FMIC, Waloro 155 FP, stock rb25 FPR, FP is unknown, A/F Ratio is unknown, haven't bought wideband yet, stock new oem injectors, running about 10psi boost, using bcpr7eix plugs, royal purple engine oil, wireing specialties harness swap, it sounds like and ignition problem I know im not running lean cuz I can modify injector plusle width + or - 20% and when I add fuel it gets way worse to the point of the engine completely missing and spitting for a second around 5k

[CurleyMerkin14]

not sher if you fixed this problem yet seen you went through alot ... i know this might sound dumb but i ran those same spark plugs on my rb25 at high rpm and higher boost they would do exactly what your saying happens to you so i had to go back to my stock plugs ill get the numbers for y u if you wanna try this .

[SkylineHatch]

where u talking about the bcpr7eix plugs?

[SkylineHatch]

I did go to a colder plug than stock but I also increased boost by a few pounds, it almost sounds like an incomplete burn or something, shud I have gone one step colder if I just have simple bolt ons?

[SkylineHatch]

Hey man I been having the same issue except a bit worse, it spits at 5k and up everytime and its because ur maxing out ur maf, then u run lean detonate and the pcm retards ignition timing and u lack power, I watch it all happen live through scan tool while I was wot ib the car, my maf read 5v by the time I hit 4800 rpm