My cars had a habit of lightly smoking at idle. However lately it's gotten worse.
When i'd stop the car, a giant cloud of oil smoke would come out of the car for a few seconds, then it'd fade away. I replaced the PCV, they were bad, the springs didn't keep them closed. So the new PCV seem to help. didn't smoke much at all the next few days. Now it's seems back with a vengance. It smokes evenly thru both tailpipes as well. And yes, theres oil in the plenum. And no oil on the turbo outlet pipes to the plenum

It does not smoke under boost or acceleration. only during high vaccuum. At least not that i can tell. I only see the big cloud when i stop the car or slow down.

I'm going to bypass the PCV today and see what happens.

What else could be wrong?



Edited 1 time(s). Last edit was 2009:07:03:08:44:12.

turbos are starting to leak. if you get no smoke under boost/accel then it is likely your turbo seals on the exhaust side. drop one of your downpipes if you can and see if there is any oil inside the exhaust housing of the turbo.

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I have Lived and Learned to LOVE... MY Z

zazupilot: you are luminar - slayer of Z's
1991zed: "i have a dual hks exhaust that gives me a good 30hp"
Ballistic: "A lime green Lambo with black wheels: The car of choice for the efeminate guy with the tramp stamp who wants to be a bada$$. Just say no to pillowbiting."
Ballistic: "Be sure to tell someone at your job that he's an idiot. Then stay away. Idiots self-destruct at any given moment."
YOU + ARE = YOU'RE. THEY + ARE = THEY'RE YOU ILLITERATE BASTARDS

I know most here don't think it makes a difference, but the weight oil you use can cause a problem. Since its summer, and hot, try changing to a heavier weight lubricant. If you have a mechanical problem, changing to a heavier viscosity probably won't help, but it won't hurt anything either. I use 20W50 Racing or Synthetic year round in everything I own and none of them smoke. Yes everything.

1993 Nissan 300 TT 86K
1990 Nissan 300 NA 28K (8K racing)
90/96 Nissan 300 GT-2 2K
2006 Honda Civic 31K
1988 Golf cart ??
2000 Ford Van 5.4 143K
4 stroke Lawn mower, edger, tiller. All over ten years old.
5 speed Nissan transmissions.

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Old guy

@Luminar
why would both my turbos start to leak at the same time?

Regardless, i suppose i could try taking off the downpipe

Valve stem seals.

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*-- Just some stuffy advice from a crabby old fart who's too set in his ways. --*

I capped of the PCVs with some plugs, and it sure didn't stop smoking. Almost seemed like it was worse. The smoke smells quite strongly of oil.

@JT240Z
How could i check the stem seals?

It’s hard to verify for sure. It's just very symptomatic of high vacuum oil consumption.

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*-- Just some stuffy advice from a crabby old fart who's too set in his ways. --*

Is it common to have it smoking on both sides? I guess they are in similar situations and would tend to wear about the same over both sides of the engine.

You have thin oil sucking by somewhere. Could be valves, rings, turbo seals, or PVC. An oil change to 20W50 could be your mechanic in a bottle. You have nothing to loose except the smoke.

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Old guy

I did buy some 15w50 last week to try. Perhaps i should just get some 20w50 instead.
It does seem to get worse the hotter it is outside.

I swear by the Mobil 1 15W-50 as the daily 100 degree temps here in Austin are tough and I certainly like to run the A/C. When it's over 100,at idle or very low speeds the temp guage will start to creep up over half way where it normally sits otherwise. It's worth a try to see if there's any improvement.

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'I'm not a guru but I've had my Z for 9 years'
1992 Charcoal Pearl 2+2 converted to TT by Ramey & Silvertwin: JWT Intake/ECU, HKS Exhaust, Hi-flow Cats,Underdrive Pulley, RPS Flywheel w/RPS Street Clutch, Aluminum Driveshaft, Silvertwin Shifter, Front/Rear Strut Tower Braces

20w50 in synthetic should help to reduce some of the smoke "visibility" as well. Synthetic tends to burn less but not a total cure either. Royal Purple makes 20w50 syn and so does Amsoil (don't think anyone else does?)...

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+++ John's NJ Ride +++
'91 2+2 96k miles, Chromed OEM Wheels, Chrome Plenum, JSPEC Clear Corners, Toyo Proxes 4's, U/D Pulley, Custom Mod'd Control Pods - White LED Lighting with Blue LED Indicators

I put some valvoline max life 20w50 in. drove it 30 miles. Didn't seem to change.
Sometimes when i'd slow or stop i can hear a small backfire and i get a surge of smoke.


Guess i'm going to have to try valve seals :(

did you forget to try dropping a downpipe just to be sure? you realize that valve seals requires removal of the head. it CAN be done wiht the head attached to the block, but you're going to hate life and wish that you pulled the heads.

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I have Lived and Learned to LOVE... MY Z

zazupilot: you are luminar - slayer of Z's
1991zed: "i have a dual hks exhaust that gives me a good 30hp"
Ballistic: "A lime green Lambo with black wheels: The car of choice for the efeminate guy with the tramp stamp who wants to be a bada$$. Just say no to pillowbiting."
Ballistic: "Be sure to tell someone at your job that he's an idiot. Then stay away. Idiots self-destruct at any given moment."
YOU + ARE = YOU'RE. THEY + ARE = THEY'RE YOU ILLITERATE BASTARDS

@ Luminar
Yeah, i suppose i did forget.
What exactly am i going to be looking for? there's going to be traces of oil everywhere i'd imagine since all this oil smoke is puking out.

well if its smoking as bad as you say, the turbines should atleast look wet or sort of glossy i guess. look for signs of baked oil. you're going to need a bright flashlight so you can see behind the turbine blades. also you can try a hand vaccume pump and open the wastegate for more visibility.

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I have Lived and Learned to LOVE... MY Z

zazupilot: you are luminar - slayer of Z's
1991zed: "i have a dual hks exhaust that gives me a good 30hp"
Ballistic: "A lime green Lambo with black wheels: The car of choice for the efeminate guy with the tramp stamp who wants to be a bada$$. Just say no to pillowbiting."
Ballistic: "Be sure to tell someone at your job that he's an idiot. Then stay away. Idiots self-destruct at any given moment."
YOU + ARE = YOU'RE. THEY + ARE = THEY'RE YOU ILLITERATE BASTARDS

Had a friend who replaced his smoking 200+K motor with a new crate motor from GM. After the new motor warmed up it smoked too! GM gave him a replacement, and when that one warmed up it SMOKED. He found his exhaust system was full of oil from the origional smoking motor and when warmed sufficiently, it smoked. He laughs about it now, but it did take over three weeks to resolve. FYI

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Old guy

thats why you should pull a downpipe =]

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I have Lived and Learned to LOVE... MY Z

zazupilot: you are luminar - slayer of Z's
1991zed: "i have a dual hks exhaust that gives me a good 30hp"
Ballistic: "A lime green Lambo with black wheels: The car of choice for the efeminate guy with the tramp stamp who wants to be a bada$$. Just say no to pillowbiting."
Ballistic: "Be sure to tell someone at your job that he's an idiot. Then stay away. Idiots self-destruct at any given moment."
YOU + ARE = YOU'RE. THEY + ARE = THEY'RE YOU ILLITERATE BASTARDS

Well i know the smoking isn't happening because of residual oil in the exhaust. I am getting WAY too much smoke for that. and it only smokes under high vaccum situations. I'm definately sucking/dumping oil from somewhere.

I will however yank one off in a bit and see about taking some pictures.

Wouldn't my plugs be rather fouled if i'm sucking in oil from the valve stems seals?

not necessarily. my turbo intake seals were blown on my stock turbos and i could kill a high volume of mosquitos for miles if i coasted to a stop and left it in gear, or just cruising smoked pretty bad too. my plugs still looked great though.

it doesnt take much burnt oil to make a terrible amount of smoke. best thing to do is to pull your intake pipes off the turbos (the charge pipe leading up to the intercooler) and inspect for oil. also looking at the turbine as you are about to do. this will verify that your turbos are not shot.

also while you have the downpipes off, you should check for any shaft play.

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I have Lived and Learned to LOVE... MY Z

zazupilot: you are luminar - slayer of Z's
1991zed: "i have a dual hks exhaust that gives me a good 30hp"
Ballistic: "A lime green Lambo with black wheels: The car of choice for the efeminate guy with the tramp stamp who wants to be a bada$$. Just say no to pillowbiting."
Ballistic: "Be sure to tell someone at your job that he's an idiot. Then stay away. Idiots self-destruct at any given moment."
YOU + ARE = YOU'RE. THEY + ARE = THEY'RE YOU ILLITERATE BASTARDS