Smoking at idle - RB25DET

Discuss the RB20, RB25 and RB26 series engines.
Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Smoking at idle - RB25DET

Postby Darius » Thu Sep 18, 2008 11:38 am

I'm running into a weird and intermittant problem that I need suggestions on diagnosing.

After the car warms up and I'm sitting at a stop light for an extended time period, the car will start to smoke and smell like burning oil. (As far as I can see from the rearview mirror) Once I rev it or start moving again, it stops smoking. Then, at the next stop light it won't smoke at all. It doesn't smoke under boost either. As far as the turbo oil feed restrictor goes, ATP told me not to add one other than what was already in the T04Z center section. I can't get it to do it when I leave it running in my driveway either.

At stop lights I'm running pretty rich (13.4-13.8) probably because my PFC initialization didn't take very well. I have HKS cams with the EXH cam gear set at 2* retarded.

Also, I have an oil leak at the sandwich filter that I haven't quite tracked down yet and it has coated the underside of my car with "rust inhibitor"


User avatar
240z4u
Posts: 2071
Joined: Mon Feb 21, 2005 4:47 am
Car: 95' 240sx

Re: Smoking at idle - RB25DET (Darius)

Postby 240z4u » Thu Sep 18, 2008 12:04 pm

Are you running a catch can? I wonder if your not pulling a bit of oil in through the intake manifold while idling for some reason. Are you running a PCV valve?

I am assuming you have pulled an i/c pipe to check for oil right?

My car also has a nice coat of rust inhibitor on the bottom of it! lol

Evan

BTW, how pronounced is it? And is your oil level dropping? Are you overfull?

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: Smoking at idle - RB25DET (240z4u)

Postby Darius » Fri Sep 19, 2008 3:50 am

My catch can is vented to atmosphere, the PCV is plugged, it is fairly pronounced when I can see it in the rear view as a blue haze, and I have not pulled an IC pipe to see the inside of it yet. However, my BOV recirc pipe was clean. My oil pressure stays the same as does the temp. I don't think I'm overfull, but I'm not sure how that would cause it to smoke??

I'm wondering if the oil coating the exhaust is getting hot and burning off since there's no air passing by it while I'm not moving to cool it and it is not actually coming out of the tailpipe?? Is this possible?

User avatar
eh?
Posts: 1781
Joined: Sat Jan 24, 2004 2:26 pm

Postby eh? » Fri Sep 19, 2008 4:03 am

Most likely caused by the oil leak..

User avatar
Shocker
Posts: 2082
Joined: Sun Aug 01, 2004 2:40 pm
Car: 89 240sxHB rb26/30

Re: (eh?)

Postby Shocker » Fri Sep 19, 2008 4:22 am

eh? wrote:Most likely caused by the oil leak..
I'm not sure how an oil leak by the sandwich adapter would cause the engine to burn oil?

Matt I really hope your not running into the same issue that I had. Is there any line from your valve covers sucking vac off of your intake pipe? If theres no hoses coming from your valve covers to your intake and your PCV is blocked theres no way for oil to enter your IC pipes.

What you can do for a quick check is remove your v-band and take a peak at the rear of your turbine housing. That should give you an idea of the amount of oil being burnt and a better idea of the severity of it.

User avatar
Carl H
Posts: 6018
Joined: Mon Aug 04, 2003 4:09 am
Car: 1995 240SX SE RB30DET

Postby Carl H » Fri Sep 19, 2008 4:32 am

regardless of what atp tells you I've found that on most nissans you need to run a 1/16" restrictor on an journal bearing turbo and a 0.032" restrictor on bb/gt turbos.i had a smoking issue with my car till i fitted a restrictor...could also be bad valvestemseals...a few of mine are bad even tho i had them replaced when i rebuilt the engine.

User avatar
eh?
Posts: 1781
Joined: Sat Jan 24, 2004 2:26 pm

Re: (Shocker)

Postby eh? » Fri Sep 19, 2008 4:50 am

Shocker wrote:
I'm not sure how an oil leak by the sandwich adapter would cause the engine to burn oil?
Op doesn't know if it's actually the engine burning the oil. Op does know there is an oil leak from the fitting that's coating the underside of the car with oil. Oil+ hot exhaust pipes = smoke, but it won't always smoke because it not a big leak.

User avatar
Shocker
Posts: 2082
Joined: Sun Aug 01, 2004 2:40 pm
Car: 89 240sxHB rb26/30

Re: (eh?)

Postby Shocker » Fri Sep 19, 2008 5:41 am

eh? wrote:
Op doesn't know if it's actually the engine burning the oil. Op does know there is an oil leak from the fitting that's coating the underside of the car with oil. Oil+ hot exhaust pipes = smoke, but it won't always smoke because it not a big leak.
I suppose that is a good point if the leak is more central on the motor or towards the exhaust side. I was assuming he "saw" burning oil leaving his exhaust.

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: (Shocker)

Postby Darius » Fri Sep 19, 2008 6:41 am

Like eh? said, I can't tell if it is a general smoking of the exhaust system or coming directly out of the pipe itself. It never smokes when I am waiting for it.

The only way I can associate the catch can with it is if the hose from the valve covers to the can is getting pinched between the hood and something and pressurizing the crankcase. I had this issue once with a plugged filter on the catch can. Smoked like crazy.

I'll pull an IC hose off and see if there is any oil coming from the turbo. If there is, then I know it needs an additional restrictor.

And wouldn't valve seals constantly leak and smoke if they were bad? I just replaced the stem seals so I highly doubt those are bad.

User avatar
eh?
Posts: 1781
Joined: Sat Jan 24, 2004 2:26 pm

Postby eh? » Fri Sep 19, 2008 10:19 am

Because it's intermittent, I think it's the oil leak. But I would go ahead and pull your spark plugs and pull your o2 sensor and check for oil fouling.

User avatar
Shocker
Posts: 2082
Joined: Sun Aug 01, 2004 2:40 pm
Car: 89 240sxHB rb26/30

Re: (eh?)

Postby Shocker » Fri Sep 19, 2008 12:05 pm

eh? wrote:Because it's intermittent, I think it's the oil leak. But I would go ahead and pull your spark plugs and pull your o2 sensor and check for oil fouling.
Yup, while the plugs are out use a little magnet and scape the tops of the pistons see what kind/if any residoo comes up. Use a little light as well to take a peak. Hopefully they are nice and clean!

mott6904
Posts: 680
Joined: Tue Jan 30, 2007 2:50 pm
Car: rb20 big turbo big cams s13, 97 kouki, turbo audi a4,turbo busa

Re: (Shocker)

Postby mott6904 » Tue Sep 23, 2008 3:09 pm

Is your oil level to high? It might be a stupid question but can be overlooked very easy.

User avatar
pawpaw18_00
Posts: 66
Joined: Fri May 07, 2004 6:03 pm
Car: 91 240sx Hatch

Re: (mott6904)

Postby pawpaw18_00 » Thu Sep 25, 2008 9:42 pm

my .2 would be to powerspray or brake clean the suspected oil leak that way you have a clean area...to rule out oil burning on the exhaust...other than that i cant see why using a restrictor on the oil line to the turbo oil help? because at idle oil pressure is very low...just an idea...

aux9050
Posts: 1
Joined: Tue Jan 22, 2008 10:33 am
Car: rb25det 89 240sx coupe

Re: (Darius)

Postby aux9050 » Mon Oct 06, 2008 3:25 pm

Hey Darius did you find out anything else about the problem? I'm having the same issue, mine is coming out of the exhaust itself though and it only happens when I'm in gear comming to a stop and I switch to neutral, the longer I live the car on gear while slowing down the more smoke comes out. I'm not running a catch can either. Any help would be appreciated.

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: (aux9050)

Postby Darius » Mon Oct 06, 2008 5:12 pm

I finally saw this happen while I was outside the car. I was sitting in line for the ATM and it started to smoke so I got out and noticed that the smoke was coming from the tailpipe.

It always seems to happen when the car is idling for an extended time period like at a stop light. Then, it goes away when I start driving again. I'll get to the next stop light and it won't be smoking.

I don't know. I'm going to change my plugs to 7's, set my exhaust cam back to zero retard (at 4* now), do the idle relearn, and recalibrate my wideband O2.

Yellow4g63
Posts: 3717
Joined: Mon Jan 20, 2003 6:07 pm
Car: 95 RB20 240, 91 NX2000 VE power, 95 Stock 240sx
Contact:

Re: (Darius)

Postby Yellow4g63 » Tue Oct 07, 2008 2:41 am

Turbo oil drain problem?

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: (Yellow4g63)

Postby Darius » Tue Oct 07, 2008 3:02 am

I wouldn't think so. I have a -10AN drain line on there. That should be big enough, right?

Another thing I am considering is that when the car is sitting still, the rubber hoses I'm using for my catch can are getting hot and collapsing and causing the crankcase to pressurize and blow oil past the rings. The hoses are all a big cluster f__k until I can get them swapped out for braided this winter. It smoked in a similar fashion when I had a breather filter on the catch can and it clogged with oil residue.

User avatar
240z4u
Posts: 2071
Joined: Mon Feb 21, 2005 4:47 am
Car: 95' 240sx

Re: (Darius)

Postby 240z4u » Tue Oct 07, 2008 3:33 am

-10 is perfectly fine.

I think you found your problem. The question is, why are they collapsing so badly? I would just replace them with fresh hose for now. Maybe they are breaking down slowly.

Evan

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: (240z4u)

Postby Darius » Tue Oct 07, 2008 4:02 am

They're not reinforced hose so they kink when they bend. I'm just going to get those metal coil things that keep the hose from squashing when it's bent. It'll look janky as hell, but I don't care at this point.

User avatar
240z4u
Posts: 2071
Joined: Mon Feb 21, 2005 4:47 am
Car: 95' 240sx

Re: (Darius)

Postby 240z4u » Tue Oct 07, 2008 4:21 am

At some point function comes over form. For an example check out how nasty my engine bay looks.

Dirt = use. lol

Hope thats it!

gawdzilla
Posts: 2028
Joined: Sat Sep 18, 2004 11:51 am
Car: none

Postby gawdzilla » Tue Oct 07, 2008 4:40 am

try pinching the hoses and see what happens?

my catch can is vented to atmosphere with a 1.5" diameter breather filter. when i track the car and pull back into the pits, it always smokes at the filter. i think the filter just clogs easily or something

boostedh23a1
Posts: 281
Joined: Tue Oct 17, 2006 1:37 pm
Car: Datsun 240Z
Datsun 280Z
Location: Beaufort, SC

Re: Smoking at idle - RB25DET

Postby boostedh23a1 » Sat Jan 17, 2015 10:00 am

what did you come up with?

User avatar
chad b.
Posts: 311
Joined: Fri Nov 21, 2008 12:17 am
Car: chocolate chip kouki
Location: Mobile, AL

Re: Smoking at idle - RB25DET

Postby chad b. » Sun Jan 18, 2015 2:11 am

Dude, the original post was made 7 years ago and that car has been sold. Talk about digging up an old post!

Darius
Posts: 4820
Joined: Sun Mar 02, 2003 9:48 am
Car: RB25DET S14 - 665 WHP
Location: Chicago

Re: Smoking at idle - RB25DET

Postby Darius » Sun Jan 18, 2015 9:06 pm

hahaha yeah plus, I think I posted that the problem was a plugged filter on my catch can that caused the crankcase to pressurize. I ditched the filter and just ran an open tube down to the bottom of the car so it could drip if it needed to.

julio
Posts: 374
Joined: Fri Oct 06, 2006 1:18 pm
Car: RB26 AWD converted S14

Re: Smoking at idle - RB25DET

Postby julio » Mon Jan 19, 2015 11:05 am

My car has the same issue after coming off a high boost run and mine are VTA as well (straight vented, no reducers or anything of the sort). You can even see it during a pull on the dyno. Normally I would be worried about this, but the engine is freshly rebuilt and compression is solid across the board. I personally think the screen baffles in the valve covers do too good of a job at making sure oil doesn't get past them, causing a restriction.

I really want to install a vacuum pump someday to see the difference on a dyno. I've heard of decent gains from removing the pressurized oil mist out of the block, not to mention the issues it can cause with your seals...

RRRRB
Posts: 758
Joined: Wed Jun 01, 2011 9:31 am
Car: 98 RB powered S14
Location: WA

Re: Smoking at idle - RB25DET

Postby RRRRB » Mon Jan 19, 2015 11:53 am

I think some of it as long as it's brief is from the seals in the turbo being loaded and unloaded a little oil gets thru, I have a precision turbo and it does the same thing, I just replaced a head gasket and really looked over the engine and not a hint of oil in the exhaust ports etc.. smoke generally doesn't happen at idle from rings it's usually a stem seal or a bad turbo or poor draining..


Return to “RB20DET / RB25DET / RB26DETT Forum”