Stutter at 8psi...

[BoostInnovations]

Well I have a 95 240sx with S13 SR20DET with Z32 maf, stock ecu(yes i know i need a daughterboard), 3'' exhaust, FMIC, Greddy Intake Manifold, and Greddy Profec B Spec II boost controller, and SAFCII...It accelerates fine at 6psi and under with partial throttle....i can rev all the way to redline just fine...if i go full throttle and it hits 7-8psi or so it stutters(doesnt matter what RPM either) and sounds like its backfiring...at first i thought it was my BOV which is a type S because it was backed off a long ways but i checked and it had been tightened all the way...What do you guys think it is? If it was a boost leak it would be weird for it to leak at 7-8psi and not 6psi...IDK give me your input please...Thanks in advance...


Thanks,
Tony

[TheSnail]

What fuel pump do you have?

[BoostInnovations]

stock...oh shit could it be fuel cut or no? The AFC isnt tuned its just set to 0 so its taken outta the system...

[TheSnail]

That is the problem. Change the fuel pump and you will be happy.

[BoostInnovations]

i have a walbro that came with the car...but do i need an install kit for it cause i dont think i can find anything for it just the pump...?

[BoostInnovations]

anyone?

The message you have entered is too short. Please lengthen your message to at least 10 characters.

[Bdubs]

To install the walbaro, just get the s13 install kit and reuse your stock sock, or buy a new OEM nissan fuel sock. Its real simple, cut and splice two wires, reattach the OEM fuel sock, for the s14, because the s14 tank is at an angle, and your good to go.

[BoostInnovations]

why would i get the S13 install kit for an S14?

[S14DB]

why would i get the S13 install kit for an S14?
cause there is no s14 install kit.

[BoostInnovations]

oh thats gay

[BoostInnovations]

well i installed the walbro 255lph HP pump tonight...didnt seem to fix the problem...it might have gotten a little better but its definately still there...anyone have any ideas? it only happens at full boost and WOT....if i am not spooled all the way at WOT it doesnt have any problems...and it seems as it gets higher in the RPM range it starts to get worse...could it be timing or plugs?

[TheSnail]

Spark plugs

[rokmplutonium]

My s13 makes a backfiring noise too. If you change your spark plugs, and they work, let me know.

[rokmplutonium]

I'm going to try out the NGK V-cut racing plugs

[BoostInnovations]

do i need to get colder plugs than just the sentra or does the standard heat level work fine?

[blue109]

have you checked injectors? one of mine crapped out and it did the same thing. use a multimeter on the leads in the injector and check resistance. i forget what its suppose to be at, but you can search around. or just check them all and if one is different, than theres your problem.

[BoostInnovations]

alright i will also check that out as well...

[KOUKI KA-T]

check the gap on your plugs, sounds like your blowing out the spark.

[BoostInnovations]

yeah we were kinda thinkin that last night but the head was too hot to pull the plugs and it was already 145am...the guy i bought it from said they were iridium plugs but it has been sitting for a while and it has never run right...(he had problems that he didnt realize)...do iridium plugs need to be gapped? i know some plugs can be left the way they are but what is the recommended gap?

[BoostInnovations]

anyone with the gap?

[DeatschWerks]

For that boost level, 0.030" should be plenty small. Iridims may be able to produce spark at a larger gap than that. But I always stay with NGK coppers.

[BoostInnovations]

yeah i just got v-power NGKs and i believe they come gapped at .044

[BoostInnovations]

ok well i checked the gap on the plugs i put in and they were .030 and i took it out for a drive and did the same thing...basically did it at 4k and then it kinda got passed it and hit 5-5.5k and then sputtered and popped again...i didnt get a chance to check the injectors yet but the plugs that i took out were completely blacked out...it was pretty...

edit: is there any chance my Z32 MAF is causing this? It is an unchipped stock ECU...and i put in BKR5ES plugs...are those the wrong heat range...?

[BoostInnovations]

please someone help....how good of a chance is it that its the timing...?

[TheSnail]

The ones you had were were fouled. If you take your new plugs out, Im sure they will be white or light bronze. The new ones you got are probably too hot. Does it feel like you are hitting fuel cut? It is only under load right?

[BoostInnovations]

yeah it is definately only under load...it seems too constant to be fuel cut...I have never had to worry about fuel cut because my last car had dual intank walbros...and if i keep it hammered it does it really fast a bunch of times...its like its backfiring...like i almost feel like its the timing...yeah i know they were fouled...it had been sitting for a long ass time...i cleaned them up...i spose i could put em back in and see if that heat range is better for the motor...hmm

edit: what happens to timing if you adjust the CAS without the TPS unplugged? or do you not need to unplug the TPS on the S13 motor?

[broken_s13]

I had a simular problem a couple of days ago. I was driving down a bumpy road and my car started to bog at 4000rpm. When I just ease on the gas slowely it would run fine until i give it more than 50 precent throttle and boost, then it would bog again. Turns out that an intercooler clamp shooke loose. The sleeve was tight so it was holding some boost, But would leak after it couldent hold any more and cause it to bog. Black spark plugs usually means that ur running rich. Which also gives me reasin to belaive that you have a boost leak somewere. So check all your intercooler piping. I hope this helps.

[g2ic02]

Sounds like a boost leak...Pick up some t-bolt clamps and make sure they are damn tight... I am not sure that you can run a z32 mafs with out proper tuning(Maybe someone else can chime in on this one)

[s13dan]

i had same problem but even after i got a fuel pump(255) then i re-wired the 255 and all was good if that dont work O2 sensor would be my next geuss

[BoostInnovations]

see i did check for boost leaks the other day but its hard when i didnt have anyway to pressure test it...i have mostly all T-bolt clamps on there already...and my car smells lean and looks rich...thats what someone else pointed out to me...but yeah we thought boost leak too but idk...with the timing being off would the boost drop at all? I know when it pops and stutters the boost kinda drops some...i wish someone was local that had a good amount of experience with this could come and ride in it...I appreciate everyones help in this...

[BoostInnovations]

i had same problem but even after i got a fuel pump(255) then i re-wired the 255 and all was good if that dont work O2 sensor would be my next geuss

yeah i put in a pump and new plugs(they may be too hot tho) and it seemed to raise in the RPM band...

[statik]

i had same problem but even after i got a fuel pump(255) then i re-wired the 255 and all was good if that dont work O2 sensor would be my next geuss

O2 is in open loop at WOT

[BoostInnovations]

O2 is in open loop at WOT

yep good call...so im gonna try timing it and then go from there i guess...idk wtf is going on

[BoostInnovations]

ok i timed it and it was pretty far off...but after i did that i did some pulls and it was still doing the same thing except in first gear it wasnt really making much noise just kinda not pulling after 5k...and then when i was driving around i looked at my AFC and i noticed it was only reading 69-70% throttle when i had it pinned...does that usually mean bad TPS sensor? Would that be to blame for any of this?

edit: i checked the injectors and their resistances were all like 11.5-11.8ohms...that sounds right doesnt it?

[BoostInnovations]

just to update again...i went out and did some interstate pulls and it is a different beast...i could rev it to 6500 without having any popping but at that point it would pop again...the TPS managed to read 75% this time i saw atleast once or twice...what do you guys think?

[BoostInnovations]

cmon someone has to know why it only reads 70-75%

[S14DB]

cmon someone has to know why it only reads 70-75%
Bad TPS or Bad AFC install. Turn the car on but don't start it. Then back probe the TPS sensor as you go thru the whole throttle sweep. From Idle to WOT. If the TPS reads out the voltage sweep then its a bad wiring job on the AFC. If it stops going up/reading up at 3/4th throttle then I would say the TPS is fried.

[BoostInnovations]

just did it and i got from .23 at 0% to 3.84 at WOT...yeah that sounds bad to me...

[S14DB]

yep, your TPS is done for. TIme to buy a new one.

[BoostInnovations]

does the sentra one work? or what one do i need?

[caall99]

couldn't he just turn the tps to get it to .45V and 4.06V? it seems the numbers that he is getting means the tps is out of adjustment. i may be wrong.

[BoostInnovations]

i adjusted it to .45v and i got 4.05 on the WOT side...so huh musta just been outta adjustment...weird thanks for everything guys!!

[S14DB]

hum, looking up the Numbers doesn't seem that bad now. Should be 0.3-0.7v closed and approximaely 4.0v open. The AFC should read 0% at idle and approximaely 84% at WOT. So, the value should be fine. I don't think the AFC is hooked up to the right wire on the TPS thou. TPS wire is 0.3v-4v The TPSS is 0.4-3v, TPS power should be 5v constant and ground 0v constaint. I think your AFC my be hooked upto the TPSS not the TPS. That or the connection is not good to the AFC.

[caall99]

haha, i was off by .01V when open. i guess my simple math was good! :coold:

[BoostInnovations]

well i got it to read 100% on the AFC but my throttle cable mount is ghetto and hits the hood so now im trying to figure out a way to fix that...btw i did not do the swap or anything...i bought it as is for a project...looks like i might be on my way to getting it perfect...or atleast almost perfect ;)

[BoostInnovations]

ok i am really confused now...got it all figured out as far as the TPS goes but it still pops at 6500...seriously im starting to get pissed off...would the timing have changed with me changing the TPS Sensor at all?

[BoostInnovations]

anyone before i take off?

[BoostInnovations]

why would it still be popping and sputtering at 6500? I wouldnt expect the Z32 MAF to affect it like that would it? How about too hot of plugs? I only got the 5 range plugs cause i didnt even think of it when i went in there...

[TheSnail]

I been thinking sparkplugs from the get go.

[BoostInnovations]

i just checked my plugs and they are fouled out once again...i guess i could try a colder range...maybe the iridiums that were in there were too hot as well...do you think the timing would have changed with adjusting the TPS? err shit just a thought...if my TPS was never reading WOT then would it may be hitting fuel cut at 6500...cause you really shouldnt be revving to 6500 unless its at WOT...does that sound at all possible?

[BoostInnovations]

is there any chance the maf is wired wrong? is the car supposed to be able to run without the maf plugged in? I'm pretty sure i drove it with the MAF unplugged before i bought it cause he was like oh i spose we could try it with the MAF plugged in...

[BoostInnovations]

might as well bump it up...

[canadians1412345]

Go to a bkr7e11 ngk plug.

My car is stuttering at full boost at 7 psi, but only between 2500 and 4500 rpm. Above that it's all fine. I have a stocck fuel pump, and it certainly isn't clutch or diff slip or any sort.

I went from a stock plug to the bkr6e11 ngk's, it got better, but not fixed. So I'm gonna step colder to a 7, and gap to .030. I'd try that, after that check your wiring.

[BoostInnovations]

thats what i was thinking...thanks

[BoostInnovations]

i put in the new plugs and it got better but i also found out that the IACV was not connected to the UICP like it was supposed to be so that was like a 5/8'' boost leak...that seemed to stop the motor from drowning in fuel at WOT but it still pops at about 6250+...i am gonna check for more boost leaks and see how that goes

[BoostInnovations]

Oh shit. I just unhooked my MAF and found i could rev in neutral all the way to the limiter...WTF?!?! I thought you could only rev to 2500 with it unplugged? I am really confused now..also it found that my IACV is not even wired in...wtf? Do I need that at all? If I do how am I supposed to wire it up? Just let me know.

Thanks again,
Tony

P.S. If you are in the area of Fargo, ND/Moorhead, MN and you know your SR's let me know...

[drifter808]

It sounds to me like your MAFS is broken or the wiring is incorrect or your timing is to advanced. My SR had the same problem in 1st gear i could rev it clear to redline then in 2nd to 5th i couldn't rev that high before the engine would stutter. I put a timing light on it and found out i had to advanced timing. fixed it and it worked fine until driver error blew up the engine :doh: But definently check your timing again and if anything maybe retard it a bit.

Also is your AFC programmed to the Z32 mafs sensor?

[BoostInnovations]

ive timed it more than once...it is dead on accurate with more than one persons eye looking at it...the AFC i know is programmed right since i had to correct it when i bought the car...

[BoostInnovations]

The ECU i found in the car was a Garage Fukui ECU without a chip in it uh oh...this was the last thing I checked because he told me he put a new one in just before I bought it so i figured it was fine...i rechecked the harness and a bunch of sensors etc and i found the knock sensor unplugged...so thanks for all your help I appreciated it!! this is a direct copy from another forum:

just to put some closure on this...the garage fukui ECU used to be chipped but it was missing...well the resistor was never changed back either...so that means the ECU was trying to read a daughterboard that wasnt there...tomorrow morning I am taking the ECU to get the resistor moved even tho I have another ECU on the way...just to see if it works or not...i also found that my knock sensor was completely unplugged and the plug wasnt even wired in...I also ordered a new CAS which should be here tomorrow afternoon sometime...but i will try the resoldered ECU first...i cannot believe i NEVER even thought of that until today...if nothing else i have learned alot about how SR's arent supposed to run

Thanks,
Tony

p.s. Wish me luck

[BoostInnovations]

everything works and it pulls nicely...thanks for the help!!