Breaking up while in boost

[KEMP]

it feels like its breaking up a bit, once i hit about half of my set boost, it desides to act like a boost leak or something like that, like a fluttering weird noise, i have checked for boost leaks and vacuum leaks, nothing seems to be there.

Any ideas? thanks

[sjbsuperman1425]

sounds like ignition or fuel to me, but i could be wrong..

[KEMP]

ya, but im not sure what it could be, it just up and did it on the first real cold night.

Plugs maybe?

[sjbsuperman1425]

i'd start there, mostly because its really cheap to do.

[KEMP]

ok, plugs changed and gapped.

runs better, but still does it.

any ideas? its almost like its cutting some sort of fuel or spark....

[sjbsuperman1425]

running rich at all? how did the plugs look? do you have a walbro and no fuel pressure regulator? is the cut out like a sort of backfire, or is it more like a boost leak?

[KEMP]

i

running rich at all? how did the plugs look? do you have a walbro and no fuel pressure regulator? is the cut out like a sort of backfire, or is it more like a boost leak?

it runs decently rich, it pops fire. the plugs looked kinda crappy and signs of carbon. it has a 255walbro on stock fpr, but it has ran perfect like this for a couple months....it sounds like a back fire sometimes, but kinda like a mixture between both sounds.

i have been told by one of my buddies with an rb25/26 that this happened to him and it was a coil pack...

[sjbsuperman1425]

yea it could be a coil pack. i know that my car cuts out a bit when coming on boost because it runs rich with the walbro and stock fpr. my guess is on that. thats why i just bought a nimso fpr and a gauge for when i get mine on the road next year.

IMO, i'd say try the FPR, mostly because its probably running rich anyway and it'll save on your plug life, and if the problem still persists, start going with the coil packs. but my money is on fpr being to high.

[mbmbmb23]

i

i have been told by one of my buddies with an rb25/26 that this happened to him and it was a coil pack...

Borrow a coil pack from someone or grab one from a Pulsar NX SE and try swapping that one for each of yours in turn. If it doesnt fix it, double check your timing.

[KEMP]

yea it could be a coil pack. i know that my car cuts out a bit when coming on boost because it runs rich with the walbro and stock fpr. my guess is on that. thats why i just bought a nimso fpr and a gauge for when i get mine on the road next year.

IMO, i'd say try the FPR, mostly because its probably running rich anyway and it'll save on your plug life, and if the problem still persists, start going with the coil packs. but my money is on fpr being to high.

ya but what it weird is it just up and did it randomly, it ran great for the 2 months ive had it.

what psi should the fpr be set at

[KEMP]

Borrow a coil pack from someone or grab one from a Pulsar NX SE and try swapping that one for each of yours in turn. If it doesnt fix it, double check your timing.

will do

my buddy has a couple coil packs from his RB, arent they the same coil pack? could i use that.

[sjbsuperman1425]

fuel pressure should be at 36.3psi IIRC? no RB coil packs from what i read, they use different plugs/connectors. if it just up and did it, it doesn't seem like it'd be the fpr, unless it just went out, but im not sure. welcome the start of process of elimination!

[ca18detgabby]

yes the rb coils are the same

a coil is less probable if it is in boost........ in vac you are running strickly compression and make it far more noticable. HOWEVER, they are real easy to check and test, so always good to make sure they are good.

i would check the Fuel pressure...... make sure it is set per the FSM

could be a small vac leak that is more noticable under boost as the increased pressure.

could just be that your a/f is off.

could be that that you are pushing the turbo passed its effieceny. most will note a peak point of 5500RPMs(ISH) and then drops from there in the RPM band as the turbo is under sized.

telling us a bit about your build and anything you have already tried......

[KEMP]

yes the rb coils are the same

a coil is less probable if it is in boost........ in vac you are running strickly compression and make it far more noticable. HOWEVER, they are real easy to check and test, so always good to make sure they are good.

i would check the Fuel pressure...... make sure it is set per the FSM

could be a small vac leak that is more noticable under boost as the increased pressure.

could just be that your a/f is off.

could be that that you are pushing the turbo passed its effieceny. most will note a peak point of 5500RPMs(ISH) and then drops from there in the RPM band as the turbo is under sized.

telling us a bit about your build and anything you have already tried......

well it builds boost fine, its just if i get on it quick, like in 4th gear cruising into boost, it will hit full boost no problem, which is why i think its the coil, because the spark cant keep up with the quicker revs.

it is boost leak free, and its stock FPR, so its not adjustable. and i am DEFINETLY not pushing the turbo past its effic. TRUST me, haha

and how do i check the coils?

new plugs, checked for boost leaks, checked for bov leak, checked for intake/maf leaks.

[ca18detgabby]

and how do i check the coils?

new plugs, checked for boost leaks, checked for bov leak, checked for intake/maf leaks.

is the bov blowing its load early and releasing pressure?

unplug a coil....... if nothing changes........... it is bad. if the idle and run condition worsen. then it is still good

pretty much an all or nothing thing. a blown coil shuts down an entire cyclindar as it wont spark at all. as the old addage you need fuel/air/ AND SPARK for combustion. Cut any one out and you have nothing.

[sjbsuperman1425]

gabby, i didn't think the RB coil packs were "Plug and Play" with the CA. my friend has a RB25 and his aren't the same as the CA?

[ca18detgabby]

gabby, i didn't think the RB coil packs were "Plug and Play" with the CA. my friend has a RB25 and his aren't the same as the CA?

the CAS are the same as well. Im almost postitive the RB coils are the same.....

[KEMP]

the CAS are the same as well. Im almost postitive the RB coils are the same.....

the RB20 coils are the same, and every RB CAS is the same, same part number.

other RB coils will work if cut with RB pig tails...

RB20's are plug and play.

[KEMP]

is the bov blowing its load early and releasing pressure?

unplug a coil....... if nothing changes........... it is bad. if the idle and run condition worsen. then it is still good

pretty much an all or nothing thing. a blown coil shuts down an entire cyclindar as it wont spark at all. as the old addage you need fuel/air/ AND SPARK for combustion. Cut any one out and you have nothing.

well on my friends RB, his ran, and idled fine until he hit mid boost, because the coil was not completely bad, but coulndt keep up with the quicker/higher revs...

he replaced it, and it ran fine, same symptoms i have as well...

[dattodude]

rb25 CAS is the same as CA18?

Wouldn't the 6 cylinder one have 6 holes in it?

The CA18 CAS has two rows of holes in the trigger disk, 1 degree and then a hole every 90 degrees.

Be weary of this CAS advice. :-)

[mbmbmb23]

well on my friends RB, his ran, and idled fine until he hit mid boost, because the coil was not completely bad, but coulndt keep up with the quicker/higher revs...

he replaced it, and it ran fine, same symptoms i have as well...

Well...dont use the bad coil pack that was failing him before he switched to the new unit. The advice of unplugging the coils one at a time to see which doesnt make the engine run worse is okay if the coil is not firing at idle....but yours are evidentlly......you have 4 cylinders firing so you need to swap each coil out one at a time and go for a drive....doing the same "drive" each time and see how the car acts with each of the 4 coils swapped out for a known good one.

[KEMP]

Well...dont use the bad coil pack that was failing him before he switched to the new unit. The advice of unplugging the coils one at a time to see which doesnt make the engine run worse is okay if the coil is not firing at idle....but yours are evidentlly......you have 4 cylinders firing so you need to swap each coil out one at a time and go for a drive....doing the same "drive" each time and see how the car acts with each of the 4 coils swapped out for a known good one.

so i bought i new coil pack. i put it in each cylinder and went for a test drive, 4 times, did the same thing, checked timing, it was about 16ish, i put it on 11, because retarding timing is safer, and i just wanted to see if it would help, it felt a bit better. 1-3 gear didnt it bad, 4-5 felt fine and full boost until about 4-5k rpm, and i let out.

I have no idea what this could be, can anyone help?

[mbmbmb23]

Hmm...you have a walbro and stock FPR....I wonder if that stocker isnt working right as the pressure increases? You said it pops and the plugs are black. You are either getting too much fuel or not enough spark.

[sjbsuperman1425]

you should get the NISMO FPR. it might solve the problem, and is a nice thing to have for when you get bigger injectors and so on. The Nismo Shop sells them for 116 shipped.

http://www.thenismoshop.com

[meminto]

I assume its a jdm ca18det with jdm computer?

And on a cold night you hit WOT and it feels like bunny hopping?

Are you using a boost controller?

Has the computer been remapped?

I have an idea as to the cause, but I need these questions confirmed lol

[KEMP]

I assume its a jdm ca18det with jdm computer?

And on a cold night you hit WOT and it feels like bunny hopping?

Are you using a boost controller?

Has the computer been remapped?

I have an idea as to the cause, but I need these questions confirmed lol

hks evc 6 bost controller, stock mapped ecu, and its not a spike, because it does it contantly if hts what your thinking.

and if it were the FPR why would it just up and do it one night. it runs rich as hell, from the sound and confirmation of fire out of my exhaust.

someone said it could be the following. coolant temp sensor, ignitor chip, O2 sensor, injectors, bad fuel pump or relay.

i dont see how it could be fuel related if it just randomly did it, the car has been running like the with literall not modifications for about 2 months and ran fine, the night before i went to put on my new 50trim setup on this happened, the new turbo setup is now on, but still persists.

i need to figure this out asap

[meminto]

So what level of boost on the controller?

Too me it sounds like it is hitting the factory boost cut to stop the motor killing itself...

But if it is remapped you would expect that to be removed..

[KEMP]

So what level of boost on the controller?

Too me it sounds like it is hitting the factory boost cut to stop the motor killing itself...

But if it is remapped you would expect that to be removed..

trust me, i know what fuel/boost cut is, it is not that.

i was on like 10psi when this happen on a t25, but i had ran 14 all day on a t25 no problem, and i have hit fuel cut, its not it.

its breaking up and studdering, almost like a mis or somethign to that nature

[meminto]

Fair enough...

Next step would be running the diagnostics to see if the sensors are at least being picked up by the ecu (it won't tell you if they are faulty, just if the circuit is open or not), if you havent done so already...

You can also check the continuity on the power transistor (igniter) to rule it out..

I know you changed and gapped the plugs, what heat range did you use?

I hope you get it sorted...

[KEMP]

Fair enough...

Next step would be running the diagnostics to see if the sensors are at least being picked up by the ecu (it won't tell you if they are faulty, just if the circuit is open or not), if you havent done so already...

You can also check the continuity on the power transistor (igniter) to rule it out..

I know you changed and gapped the plugs, what heat range did you use?

I hope you get it sorted...

well how would i know if its the ignitor? and they are 6heat range, i ran the 7's when it messed up, so i went to 6's, and stayed the same.

i heard rumors about fuel pump or FPR problems could cause this, how would i know.... and also something about the coolant temp sensor.... any ideas?

how do i read diagnostics..??