once motor builds boost it doesn't want to accelerate

[silviasgp06]

ok heres whats going on,

-car drives fine as long as i dont get into positive boost-i can give full throttle and boost will build to a solid 10psi(or any other set psi)-at WOT, with boost up, there is no shutter, motor sounds fine, but GOES NOWHERE -my safc is still reading air flow numbers that look no different from before this all started happening, so i dont think its the MAF,

-pretty sure its not a boost leak cause of the solid build in psi

could this be a O2 sensor issue or TPS issue, these are the only things i have not tested cause final semester stuff keeps cutting into RB time. But ill check power to it asap (what USDM car uses the same O2 sensor?)

it recently got warmer here in Texas(90ish degrees)

the car was driving pretty nice before and now it doing this, help!

if you need more info to diagnose i can provide it

[Shocker]

Sounds sort of like my old issue just recently...

Id bet on it being timing related, you base timing set properly?

Maybe your knocking and ECU is pulling timing? Do you have adjustable cam gears? (lol)

o2 sensor wouldn't do this, I doubt the TPS either.

Have you tried leaving the boost stock and seeing what happens?

[Influenced]

sounds like a timing issue to me as well.

i took a ride in my buddies rb swapped s14 with twin gt35r's.

it sounded like we were going crazy fast but just didnt feel like it.

fixed the timing and night and day difference!

[matafied]

i just went through that crap on my daily driver, turned out to be my maf. my safc showed proper flow #'s, but it reads volume also. i changed it and my problem was solved. if it's not that i would say small boost leak, you could have a boost leak and still build proper boost.

[Shocker]

i just went through that crap on my daily driver, turned out to be my maf. my safc showed proper flow #'s, but it reads volume also. i changed it and my problem was solved. if it's not that i would say small boost leak, you could have a boost leak and still build proper boost.

yeah this depends wheres hes getting his boost reading from, if its off the plenum it would generally show... would be nice if you had a wideband to watch the a/f's under boost. Help eliminate things.

[S14-NEO]

id be willing to bet dollars to doughnuts that its the MAF...the thing is alot of people on here think that just because the MAF is reading the correct voltage it is fine but thats not always the case.voltage is just a reference to the ECU but it also reads (airflow) in the form of cubic centimeters per minute..if that if of (even slightly) it can do weird funky stuff like not add fuel to build power..just my .02, its worth looking into for sure.

[Shocker]

Yeah if MAFS and easy first test might as well swap a known working one in.

Only failure I've ever had with a MAF is when it completely took a ****. Like fine one minute, then dead the next. Wouldn't even allow the car to idle.

[yokota180sx]

I SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO just had this problem

CAS fixed it, and pulling fuel with an safc made it better.

[silviasgp06]

awesome, the kind of help i was looking for.

hmm, will go back to stock boost

i will swap MAF as soon as i can.

hope its not the CAS, those little f'ers can be expensive, the gtr CAS is the same right? cause i can borrow one to test. Confused how it would cause this problem with out stuttering though.

will get a wide band some time soon hopefully.

and i am taking boost from the manifold

[S-tec Motorsports]

Seen a few things cause this, more than likey if your safc % seems fine it is not the air flow meter

however if you have that little junk rubber inlet tube on, and nothing covering up the exhaust manifold they are prone to collapsingit will rev like a na soon as you hit boost

also if your knock sensors are disconnected it will pull ungodly amount of timin after 4500. you said you had a afc, afc2 or newer perhaps?? check to make sure you did not mess up the knock sensor wire.

[matafied]

Seen a few things cause this, more than likey if your safc % seems fine it is not the air flow meter

i just had the same issue, and my safc was reading air flow % perfect!! and its the last thing i suspected because of it reading right. But just as

id be willing to bet dollars to doughnuts that its the MAF...the thing is alot of people on here think that just because the MAF is reading the correct voltage it is fine but thats not always the case.voltage is just a reference to the ECU but it also reads (airflow) in the form of cubic centimeters per minute

he's also the reason i suspected mine, and sure enouph it was

[gawdzilla]

hope its not the CAS, those little f'ers can be expensive, the gtr CAS is the same right? cause i can borrow one to test. Confused how it would cause this problem with out stuttering though.

probably not the CAS. if the car runs fine off boost, most likely there is nothign wrong with the CAS. it could be that your CAS is clocked wrong though (timing). timing plays a huge role in how the car runs. i've had the same issue where my timing map was way off. car sounded awesome but was not fast at all.

Do the MAF first, then check your base timing. then check for boost leaks and get a wideband. then check your timing belt alignment

[S-tec Motorsports]

I dont know where you all have been gettin your info but your wrongcan it be off scale low? yeshigh yesnot work at all yesread airflow not a chancethey are hot wire sensors. for those of you who do not know what that meansit has a wire in it. It has a theromostat in it to keep it at a constant temphow ever much voltage it takes it to keep it at that temp is its reading 0-5vwhy do cars run rich when they get dirty? because it isolates the wirethe only other thing that can break in it, is the wire to turn the fuel pump up to 12v from 8
Modified by S-tec Motorsports at 11:04 AM 4/24/2008

[silviasgp06]

i still will be checking all other mentioned systems but,

i was messing with the intake tube today and did notice its flimsyness, im almost sure that it could be collapsing from its heat weakened state. Explains why the car runs a little better before it fully warms up.

besides getting a new suction tube made is there a tried reliable way of re-enforcing the stock tube


Modified by silviasgp06 at 11:23 PM 4/24/2008

[S-tec Motorsports]

some come with large springs in them

the easiest way is do not stretch it out, collapse it, it has more material to hold it.

if you have it streached out and attached to the body somewhere, then you just found your problem

i am going to make a unedjucated guess and say the guy that changed his afm, had same problem and either attached it different place, or did not attach it at all, hense problem gone

[matafied]

i am going to make a unedjucated guess and say the guy that changed his afm, had same problem and either attached it different place, or did not attach it at all, hense problem gone

if your talking about me, i didn't move or change anything on my induction tube, i have 3 rb25 cars and can just swap what i need to for troubleshooting. all i did is remove afm and reinstall new afm, nothing different, same as it was before. but i could see it happen but that thing would have to get hotttt if it is your problem i do have an extra one laying around

[eshaze]

Hi mine has just developed the same damn problem, which sux!!! Checking all the topics covered in this thread, so what I can gather from this and correct me if i'm wrong ... if the MAF is knackard it will still drive fine but as soon as it hits boost it doesn't want to accelerate!! Mine spits and splutters when it warms up but drives as it should when cold!!

Has anyone fixed the issue??

Thanks

[gawdzilla]

MAF symptoms are very weird, and they can vary. I've had bad MAFs where the car feels like someone is stepping on the gas and stabbing the throttle on/off when trying to just cruise. I've had a bad MAF twice where the car will just shut off randomly. Give it a few seconds, and it starts back up and runs normal. If you guys can try with known good MAFs for free, I would definitely do that. If your car drove fine before and is acting up all of a sudden, check for boost leaks, then try swapping MAFs.

Hi mine has just developed the same damn problem, which sux!!! Checking all the topics covered in this thread, so what I can gather from this and correct me if i'm wrong ... if the MAF is knackard it will still drive fine but as soon as it hits boost it doesn't want to accelerate!! Mine spits and splutters when it warms up but drives as it should when cold!!

Has anyone fixed the issue??

Thanks

[silviasgp06]

still havnt had time to make a tube coil or go try another MAF but i was wondering what method you guys use for checking for boost leaks? i plan on using PVC pipe caps and valve stem to pressurized the IC piping but i know there are more ways out there just curious on everyones different methods

[S-tec Motorsports]

duct tape works too, also cheaper

[silviasgp06]

or so its not the induction tube collapsing, checking other stuff now

[perkeset]

i ran into this same problem when i first built my RB, worked it out on a dyno turned, out the fuel was so fat it was off the charts. we leaned it out and the car started running better after about 30 min on the dyno we had it tuned in. the car made boost and for the first time after building the car i felt what it could acctually do (had a boostgazm) good luck man not sure if that helps but its worth a shot