Boost Problem

[C34Stag]

The last few days I've been having some problems with the second stage of boost. As soon as I hit approx 4000rpm the boost begins to drop off. I suppose the only way I could describe it is a flutter of sorts. After doing a search earlier I've found a post that makes sense to me.

http://www.skylinesaustralia.com/forums/R3...blems+high+revs

Unfortunately its a really long post, and I can't actually pick out a way to fix it in there!

Has anyone else had this kind of problem? What should I look for that could be contributing to it?

[Big Fella]

is this car a fresh import? the plugs in mine were old and crap when i got it, slight missfire at idle, missfire like crazy at 5000rpm.

i replaced the plugs and gave all the coil pack connectors a killer clean, sillicone lubed all the coils and retryed.

Missfire was gone, car runs sweet as now.

[pyro-ns]

stageas (and i'd imagine skylines of the same era, as well) all experience a flat spot that starts around the 4000rpm mark. i haven't read all the way through his post (i'm at work), but i don't know that the second stage of the stock boost is to blame, i believe it is 100% to do with the standard tune. as for stuttering/misfiring around there, i have not yet experienced it, so can't comment.

the standard boost controller on the stagea is a relatively "dumb" unit. to the best of my knowledge (I think QWK32 will have a bit more to say on this one), the ecu flicks on the second stage of boost at the specific RPM, regardless of anything else that is happening in the engine. Apparently there is the possibility of 3 dimensional boost mapping which you can edit with Nistune, but as far as i know, the standard setup doesn't take advantage of it.

for testing purposes, i'd recommend doing the 10minute boost mod. you'll notice that the flat spot is definitely still there (it becomes especially apparently when you change near redline in first and it dumps you in the boring arse flat spot when you get into second <_<).

edit:

i just noticed that he said it was fuel + timing. i would definitely believe that, especially considering the guys on here with NisTune have taken most of the flat spot out with a tune.

[pipster11]

its probably coils

you need to take them out and give them a coat of urethane coat seal (comes in a can, i think you can get it from bunnings) its made by crc

[C34Stag]

its probably coils

you need to take them out and give them a coat of urethane coat seal (comes in a can, i think you can get it from bunnings) its made by crc

Being a complete car noob, how do I take the coils off etc? Is there an DIY section for it anywhere. I'll give that a shot later today probably. The car is a fresh import, only had it around 2 weeks. It just seems funny that it started in the last couple of days. I'll give the urethane coat a shot first, just because it seems like an easy and cheap fix! Fingers crossed its that.

[RubyRS4]

Being a complete car noob, how do I take the coils off etc? Is there an DIY section for it anywhere. I'll give that a shot later today probably. The car is a fresh import, only had it around 2 weeks. It just seems funny that it started in the last couple of days. I'll give the urethane coat a shot first, just because it seems like an easy and cheap fix! Fingers crossed its that.

This is the fun part. Your coilpacks sit on top of the spark plugs. You'll need to remove the cross-over pipe to the intake manifold, and various other little hoses that connect around it. Then remove the coilpack cover on top of the engine (wouldn't bother putting it back on ... helps keep the coilpacks cooler). Once the cover is off, you'll see the coil packs. Each of the 6 coilpacks are bolted down by 2 x 10mm bolts. Unplug the loom/connectors to the coilpacks, then remove coilpacks. While you are there, might as well put in a fresh set of plugs, seeing as you've come all this way.

Hope this helps.

[pipster11]

^^^ just like that

but try and blow out any crap thats in there b4 you take the plugs out

use a compressor or a vacuum cleaner if you don't have a compressor

if you go to the tutorials section in the main section there is probably a how-to for removing them

or google rb25 spark plug change or something like that

[STAGEA_KING]

my car got the same problem before, once it hits 5000rpm, the boost dropped down all the way.

it got a new coilpacks and aftermarket boost controller, took it down to the workshop, they couldn't fix it too.

later at night in my garage, i removed the connector of battery, so the ECU reset itself and changed a new air filter.

next day morning, reconnected the power, everything is back to normal, I felt even more power than before.

I still don't know why, but it fixed.

any idea? guys.

[chef_stagea]

dude u dont need to take the cross over pipe off...

ive done it b4... takes a bit of time to wiggle the black cover out but it does happen..!

undo the coilpacks... if you see grounding out spots on there clean em up n just see how it goes...

the coilpack missfure will be a big quick jolts... will feel like a missfire (obviously coz it is but yeah)

dont worry about spraying them, you can just tape the affected areas up with elec tape... same trick. the spray will break down with the heat.

[KiwiRS4T]

Changing the spark plugs is a good start. Get coppers NGKBCPR6ES -(and then there may or may not be 2 digits representing the gap. You want .8 but if you can only get -11 or nothing that is ok as you gan gap the plugs to .8 with a feeler guage - buy a set if you don't have one they are not dear).

Clean the coils and look for burn marks and spray and/or tape them up to insulate them.

By-pass the solenoid to eliminate any problems with the solenoid or ecu.

That should be a good start and all necessary maintenance anyway.