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View Full Version : RB25 rough idle and slow as hell


StryfeS13
02-17-2012, 12:24 AM
I'm working on my friends car that is swapped with a S2 RB25. A few weeks ago it was having a sputtering issue, so I did what most do and coated the coil packs so they wouldn't arc. This fixed that problem.

However, the car still feels extremely weak and is starting to sputter again. I doubt it's a spark issue because that problem was already fixed. I'm thinking it might be the intake collapsing, because there is no spring inside of it, and I had that same problem once on an SR. Do RB's come stock with springs in the intake tube?

Also, the idle is jumpy, it hops around non-stop unless I force it to idle with the throttle plate screw. If you rev it a few times and let it drop back down it'll idle normal for a few minutes and then start jumping again.

I also checked timing, I've read that the timing loop is inaccurate so I tested it with the cyl 1 white wire. Timing was past 30° so I put it back down to 15°, which from what I read on here is the 4th mark from the left (0°.)

Also it smokes white after revving and upon deceleration. Possibly the turbo? I've checked compression, checks out good (140,145,135,140,145,145), head gasket is not blown, so on.

Also, the RPM gauge doesn't seem to be equivalent to the motor? Could this be because it has the 180SX cluster?

TLDR; car hesitates at high rpms and is slower than a stock KA. idle is lumpy and jumps around. timing has been checked, coils have been coated, spark plug gap is at .025 (ngk bkr7e), smokes upon deceleration, compression is good, no blown head gasket.

Any ideas?

ch1873857
02-17-2012, 01:09 AM
did you redo the timing right.

rbs are very sensitive when it comes to adjusting timing. theres a specific way to do it correctly. i didnt like i normally would didnt fix my problem (similiar to your buddys) . had a buddy redo it. ran perfect afterwards.

sounds like timing or a boost leak..

Functiontheory
02-17-2012, 11:42 AM
Yes the stock tach will not work as it is for a 4 cylinder. You can get it re calibrated. I'm going to say boost leak/vacuum leak. Does he have a stock bov, is it recirculated or open atmosphere.

StryfeS13
02-17-2012, 02:26 PM
did you redo the timing right.

rbs are very sensitive when it comes to adjusting timing. theres a specific way to do it correctly. i didnt like i normally would didnt fix my problem (similiar to your buddys) . had a buddy redo it. ran perfect afterwards.

sounds like timing or a boost leak..

I did it like how I've read how everyone else does. I unplug TPS, adjust timing to 15°, and plug the TPS back in...

What is the specific way that you speak of?

Yes the stock tach will not work as it is for a 4 cylinder. You can get it re calibrated. I'm going to say boost leak/vacuum leak. Does he have a stock bov, is it recirculated or open atmosphere.

Ah alright. Any way to do that without sending the tach in to be adjusted or whatever?

Stock BOV and it's recirculated.

KendallH
02-17-2012, 02:40 PM
You can swap in a J30 or I30 tach with minimal trimming. I believe a certain year maxima tach works as well.

FutureFab
02-17-2012, 02:43 PM
A possibility on the smoke is brake fluid. Wtf?! Yes. I had a old stock master and booster back in the day and the seal went bad letting brake fluid go into the booster. Only smoked under idle due to check valve being open under vaccume.

Also sounds like timing belt is off a tooth on the crank pulley. The cam sensor bolts should be centered in the slots of the sensor housing. If its off to one side the belt is off a tooth.

StryfeS13
02-18-2012, 04:54 PM
Hey guys, I had some time to work on it today and noticed that it seems as if the exhaust cam is off a tooth. Like a tooth advanced? Can I just relieve tension of the belt with something, and turn the cam back a tooth?

Intake Cam
http://i1177.photobucket.com/albums/x343/Sickfire/DSCF8801Small.jpg

Exhaust Cam
http://i1177.photobucket.com/albums/x343/Sickfire/DSCF8806Small.jpg
http://i1177.photobucket.com/albums/x343/Sickfire/DSCF8806Medium.jpg

FutureFab
02-18-2012, 07:04 PM
You should download the fsm and go thru timing belt step by step.

180love
02-18-2012, 07:14 PM
Get a timing light and adjust ignition timing to 15*btdc.

feito
02-18-2012, 07:24 PM
stock boost? I am having the same issue with mine. I just lower the boost from 10psi to stock 7psi n it helped a lot, it's almost gone, i think i just gotta set my timing right now. I think my problem could have been rich n retard, do some research on it. I do have most stage 1 mods. Oh yeah and check your stock bov, mine was leaking baaad..

ch1873857
02-18-2012, 09:41 PM
yeah fix that base timing. relieve tension and unbolt pulley . fix and put back together. your car should run fine.

StryfeS13
02-19-2012, 12:26 AM
I took off the timing covers, removed the crank pulley, and made sure the crank and cams are timing correctly. They are all 100% now.

Also found out that the wastegate wasnt even bolted to the turbo so the flapper has probably been just stuck open this whole time...

Will start it tomorrow and tell you guys how it goes.

ch1873857
02-19-2012, 01:04 AM
Also found out that the wastegate wasnt even bolted to the turbo so the flapper has probably been just stuck open this whole time...

:eek2: msglngth

StryfeS13
02-19-2012, 02:24 AM
Yup, that was about my exact expression too. lol

FutureFab
02-19-2012, 02:21 PM
How far off was the timing belt?

jesse_s13
02-19-2012, 02:28 PM
Damn what a way to troubleshoot.


Let us know if it starts

StryfeS13
02-19-2012, 07:44 PM
Accelerates pretty good now, I also figured out how innaccurate timing an RB25 is when you try to use the white coil wire or timing loop... I had to make a custom thing to time it with.. I put a spark plug wire on the plug, attached the other end to a bolt, and put the bolt in the coil. This gave me an accurate reading, and it's perfect at 15 BTDC.

It still hunts at idle and has hard starts some times, but overall it runs better.

Any ideas on the idle or hard starts?

And I had no clue stock RB25's were so slow compared to lightly modded SR's, etc. This RB wouldnt hang with any of our other cars lol

ch1873857
02-19-2012, 08:03 PM
its just your car. My stock rb25 in my last car just had a fmic and an RB20 turbo. it was very quick and extremely responsive... gentle clutch kick in second had no problem breaking tires loose. have you done compression check.

AS240
02-19-2012, 08:07 PM
yes i'll admit they are slow as balls in stock form, but they just need a few mods to liven up. my rb25 makes 315whp on the stock turbo @ 12psi.

ch1873857
02-19-2012, 08:57 PM
what mods did you get from "slow as balls" to 315whp on stock turbo? curious..

StryfeS13
02-19-2012, 09:37 PM
its just your car. My stock rb25 in my last car just had a fmic and an RB20 turbo. it was very quick and extremely responsive... gentle clutch kick in second had no problem breaking tires loose. have you done compression check.

Nah I doubt its just the car.

I'm not used to cars under 300whp :yum:

AS240
02-19-2012, 09:37 PM
fmic, freddy plenum, 3" turbo back. tuned on a safc2. stock injectors.

ch1873857
02-19-2012, 10:07 PM
Nah I doubt its just the car.

I'm not used to cars under 300whp :yum:

oooh oooook :mepoke: