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View Full Version : RB25 PLEASE HALP!


Jumanji
05-09-2011, 03:23 PM
Hi Guys,

A mate of mine bought a R33 GTST, and its having problems currently. The turbo doesnt spool properly and it coughs and splutters and vibrates when you drive it through the rpm so from 2500 - 6000rpm. My mate always wanted one but decided that he would rather buy the first one than the right one. I think its fuel or a coilpack, any help would be great.

Cheers,

Brayden.
markdett
05-09-2011, 03:28 PM
Hmm kinda of sounds like a missfire, or even AFM. Has it got an engine light on?
Jumanji
05-09-2011, 03:33 PM
No not buy the sounds of it. it has a miss " Apparently"
R3N
05-09-2011, 03:37 PM
What's with you R33 owners and misspelling of help?
markdett
05-09-2011, 03:51 PM
No not buy the sounds of it. it has a miss " Apparently"

And its idle is rough also? Try and diagnose which cylinder(s) are missfiring (if it even is a missfire). Unplug each coilpack and see if the RPM drops or runs shitter, the one(s) with no change are missfiring.
Alt_F4
05-09-2011, 04:36 PM
My money is on the AFM, or a really bad earthing problem.
But if its an s1 it possibly could be a far gone ignitor pack.

Easy check is to borrow a known working unit in either case, usually a resolder of the internal joints and brake cleaner spray on the element will bring the AFM back to life its thats the cause.
_oz
05-09-2011, 04:45 PM
My monopoly money is on the coilpacks.
Jumanji
05-09-2011, 04:56 PM
Ok I have had a look the idles smooth as as soon as it starts to spool in gear it doesn't actually spool, and makes a real weird noise out the exhaust like the turbo is bouncing
markdett
05-09-2011, 05:12 PM
Hmm thats very wierd, try disconnecting the vacum line to the waste gate actuator and see if it will rev ok then?
_oz
05-09-2011, 06:09 PM
Hmm thats very wierd, try disconnecting the vacum line to the waste gate actuator and see if it will rev ok then?

Lol are you trying to blow his exhaust wheel off? If he does that the car will overboost..

It's most definitely an ignition problem.
markdett
05-09-2011, 06:24 PM
Lol are you trying to blow his exhaust wheel off? If he does that the car will overboost..

It's most definitely an ignition problem.

Removing the vaccum line to the turbo will cause the wastegate to stay open, not CLOSED. Therefore bypassing the turbo. Sounds weird how its not boosting.
Gonzola
05-09-2011, 06:27 PM
hmm took the vac line off wastegate actuator on a stock-ish SR20 years ago and it made bulk boost till white smoke came out the back and it his a brickwall miss... fuel cut or whatever.

I'm on the 'no vac line = lots of boost' side on this one :)
markdett
05-09-2011, 06:29 PM
*edit this may be different on non variable nozzle turbo's*

Might be best not to try it just incase. If you have a boost gauge diconnect and see if you have any boost 1st
markdett
05-09-2011, 06:32 PM
hmm took the vac line off wastegate actuator on a stock-ish SR20 years ago and it made bulk boost till white smoke came out the back and it his a brickwall miss... fuel cut or whatever.

I'm on the 'no vac line = lots of boost' side on this one :)

Yeah thought it woulda been the same with all type off turbos but obviously not. Im use to working on yd25's, zd30's ETC where they run variable vane, and the actuators work differently. Can disconnect the vacum lines to them, and you will not get anyboost.
Fujiwara13
05-09-2011, 06:39 PM
From my rb25 experience blown coilpacks wouldn't allow me to even hit 6000rpm! Although it does sound quite a lot like an ignition problem. Is there any chance you can get a reasonable quality video?
markdett
05-09-2011, 06:42 PM
From my rb25 experience blown coilpacks wouldn't allow me to even hit 6000rpm! Although it does sound quite a lot like an ignition problem. Is there any chance you can get a reasonable quality video?
+1, its pretty hard to try diagnose with out experiencing it.
_oz
05-09-2011, 07:03 PM
Theres a diaphragm inside the actuator which the boost pressure pushes against to open the waste-gate. If theres no pressure source going to the actuator it will not open the waste-gate flap.
markdett
05-09-2011, 07:05 PM
Theres a diaphragm inside the actuator which the boost pressure pushes against to open the waste-gate. If theres no pressure source going to the actuator it will not open the waste-gate flap.
Reado above, not the same as variable nozzle turbo chargers. Sorry for the mix up, but that is what im use to working with.
joshg123
05-09-2011, 08:12 PM
If you are refering to GU ZD30 'actuators' and the like, they run off vacuum varied by a purge valve as opposed to a conventional wastegate diaphram that opens with boost pressure on one side pushing against a spring on the other. Not same

Id be gapping the plugs to see if problem improves, if problem seems to get a bit better, replace coilpacks and plugs
Jumanji
06-09-2011, 07:30 AM
I've talked him into taking to hyperdrive to get an analysis on it, as I can't figure it out, i tried what you said but to no avail, I'll let you guys know what's wrong with it when I find out.

Thanks for your help :)
Orange_33
06-09-2011, 07:47 PM
boost leak? and try gapping the plugs to help with spark
DTM-031
07-09-2011, 09:37 AM
plugs or coilpacks. 25s are notorious for weak spark, especially S1
Kickit
07-09-2011, 08:43 PM
what fuel is it running? bp98 has been shit lately.. coilpacks fuck up after 4000rpm if it is them. change plugs. they could be fucked
lukevincent92
28-09-2011, 04:31 PM
i had similar problem, changed afm, problem fixed. :)
Jumanji
03-10-2011, 11:54 AM
plugs or coilpacks. 25s are notorious for weak spark, especially S1

Ended up changing the coilpacks and plugs, seemed to have removed the problem.


what fuel is it running? bp98 has been shit lately.. coilpacks fuck up after 4000rpm if it is them. change plugs. they could be fucked

Shell V Power, yeah did that it hits boost now :)