rb25det neo 4.2k rpm misfire/limit

[tridentt150v]

Can you isolate the misfire to one cylinder?

[-Jo]

will pulling out coils 1 by 1 while it idles, yeild results, as car runs smooth untill 4500rpm and idles nicely

[GTSBoy]

Best thing is pull coil plugs off while it is misfiring on the dyno.  You won't find it at idle.  If you can make it misfire a bit and then shut it off while it's doing it, you might be able to inspect the plugs and see some difference.  Might, but very far from probably.

What are your plug gaps now?  What boost is is breaking down at?  What is the condition of the coil harness?

[KiwiRS4T]

Mark the position of the CAS and then take it off and spin it by hand. If you feel roughness (like a stuffed bearing) you have a problem. So has the tuner identified and turned off launch control?

My car had a misfire on BCPR plugs and Soichi at ST Hitec got me to change then to BKR8EiX ...got mine from the US

https://www.ebay.com/itm/6-NGK-IRIDIUM-IX-SPARK-PLUGS-2668-BKR8EIX-NEW-PERFORMANCE-UPGRADE/382197340706?epid=188018740&hash=item58fcbc9a22:g:5jIAAOSwnJZZlSNO:rk:15:pf:0

and that fixed it. May not be your problem though. Is your VCT functioning properly (maybe ask your tuner - who is tuning it by the way?).

[-Jo]

hey atm my plug gap is at 0.7, im just about to go and clean and re gap them to 0.8, and i will check the cas as suggested.

i havnt taken it to the tuners yet, the car was tuned at cdm in tauranga, but ive heard some not so good things about them and theyre far away, i was highly recommended to switch to advanced tuning at hampton downs, i will be taking it to them when they get back from christmas break. 

also car feels like its hesitant when WOT

thanks for dropping knowledge on me

 

[-Jo]

now im at the point of checking cas, but im very hesitant to pull it off, incase i dont put it back on perfectly and make my situation worse... maybe ill leave that for the tuner to fiddle with if he needs to..

forgot to mention when the misfiring happens, peak boost reads 12psi

Edited December 20, 2018 by -Jo

[tridentt150v]

Taking the CAS out is fine....just mark the cas and the cover so you know where to roughly reset it.  You will need a timing light to fine tune it once reinstalled.

[-Jo]

alright i will pick up a timing light tomorrow, and do more research into how to use it and whatnot

cheers bro

[-Jo]

took it for a drive again today, boosts like shit, may shift my focus towards boost leaks, have included a small vid of a 2nd gear pull at wide open throttle. it should be accelerating much faster than this...

[-Jo]

drove it for a change midday in the hot sun, usually i go for a drive at night, seems when its hot out the car revs all the way to redline, althrough its not a smooth pull and feels a bit flat at 3k-5k rpm, but pulls good after that

does the change in air density from hot/cold really cause issues like this?

[D0gg94]

Is it running an AFM?

[-Jo]

Yea the pink sticker afm,

[D0gg94]

Maybe try cleaning the f%$& outta that with sensitive electronics cleaner or airflow cleaner? If you haven't already..

They like to play up when they get dirty it seems...

https://www.sau.com.au/forums/topic/102374-symptoms-of-faulty-afm-and-injectors/

[-Jo]

yeah gave the afm a good clean today, and the injectors were recently flow tested, so they should be allgood.

the car misfired like balls today, but last few times i drove it, it was sweet as, and the zorst likes to pop a bit now and then when throttling off, dunno what to make of it ay

idk how i didnt pay attention to this before, but noticed today the vacuum line to the bov from intake mani is blocked shut, id rather not run flutter (sounds nice tho) because dont neo turbos have nylon compressor wheels, not sure if they like it too much.

im not sure if im way off here but.. if the cars been tuned how is it now, if i reattach the vacuum hose will it cause issues? but then if its running rich itll run a bit better?

 

 

[Ben C34]

The vac line to the bov tells it to open, however when under boost also pushes it closed. Doing that will allow it to leak on boost. The obvious thing to try is plumbing it correctly. If you wan a non functioning bov you either need to block it off properly or use a one way valve on the vac line

[-Jo]

connected the vac line up and she revs out good sounds like its leaking boost pretty bad tho, hopefully not from the bov itself, ive ordered a new bov flange to weld on as old tuner mentioned the flange was a bit warped, and will leak test ic piping.

the bov is a bit to loud and high pitched for me, so might just block the line how it was and sort it all out when the flange arrives and boost leaks are sorted

 

[AngryRB]

That BOV looks ancient, I'd get rid of it as your running an atm, it's probably bleeding air off under boost and your engines getting flooded.

Also plugs make a big difference, the BKR7E's are the go as was said already.

[tridentt150v]

Try going back to a std BOV...honestly [except for wank factor] they work fine.  Lots of people have issues with am BOV's.

[-Jo]

thanks guys, il look into a way to test the bov for leaks,  how much is a stock bov worth?

 

 

[-Jo]

hey so, its been a while but ive done a boost leak test and it was losing alot of pressure way too quick, mainly bov flange and a few small leaks which tightening some clamps sorted, and welding on a new flange results in no leaks.

finally got around to getting some BKR7E's and chucking them in. honestly seems to have solved the majority of the issue, ive done about 300kms since and when at operating temp theres no  missfire and it runs how it should.

HOWEVER if its not warmed up itll still missfire at 4.5k and limits revs, which really doesnt bother me that much because i dont thrash my car when cold but still rather sort it, any ideas? ecu issue?, cold start valve? 

appreciate all the help so far, and actually enjoying learning more about the car...how deep does the rabbit hole go..