Smoke coming from under the car? Please help.

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I bought a manual Z32 N/A to restore a while back. I finally got the car running well but I have a couple problems that I can't figure out.

If me start by saying I am a beginner when it comes to cars so please let me know if you need more info for clarity.

At first, I thought my problem was oil leak related. I found and fixed a few oil leaks. Now the smell of burning oil is gone. I let the car run for about an hour to make sure oil wasn't still leaking. Everything seemed fine.... until I drove it. After driving for about 15-20 minutes, I started to notice that smoke was coming from under the car. The location were it seemed the most smoke was coming from was almost directly under were the gear shift is (sorry about the poor description, I can provide a picture if needed). Also the smoke doesn't really have a smell to it if that helps. I also noticed that it tends to smoke more quickly if driving in the city than it does on the highway. It isn't a lot of smoke, but you can see it if stopped at a light for 30 seconds or so or almost immediately after turning the car off. I wish I was knowledgeable or I could explain this better, I'm sorry. I'm happy to answer any questions you have to help me solve this problem.

performance wise, I'm not sure what to tell you. I did however notice, a small decrease in performance after the car warms up a bit, almost like a loss of power. Tell me what to look for and I'll let you know.

[t.mcginley.jr]

Is the smoke a particular color like white, blue, black, etc.?

If you see smoke coming out where the gear shift is, its probably coming from the exhaust pipes which run along either side of the transmission. The smoke is probably either coming from inside the exhaust itself, or something is dripping/leaking onto the exhaust and causing it to smoke (like oil or coolant).

Also, how many miles are on your Z?

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The smoke color is white. The car have about 210k miles on it, but about 5 months about I had the transmission replaced with one that had 34k miles on. I also replaced most of the engine as well.

Something that I did find out was that the power steering reservoir was empty and the smoke had stopped. So here is my question, is there anything in the power steering system that might be leaking in that area? Or do you think there might be another reason?

[solaire]

Look at the exhaust in the smoky area. If there's oil on it there will be a sign. If its not excessively loud its most likely a fluid leak. Especially since it stopped with fluid drain. The rack is back by that spot. It could be leaking and blowing back while driving

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I've checked for more oil leaks after cleaning up the areas and haven't found anything. So ill do as you suggested and check the rack here in a couple of hours and let you guys know what I find.

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Ok, I just checked and I definitely need a new power steering rack. But while I was looking around, I did find a very small oil leak. I believe the part is the camshaft sensor could someone verify? I had a pretty crappy picture I took since I was in a hurry to take it before it started pouring down raining, but I decided to just wait until I could upload a better picture.


This is what the oil leak appears to be coming from.



Would an oil leak actually come from this part or should I be looking somewhere else close by? Either way, I did some research on the camshaft sensor and found this:

"Symptoms
A failed camshaft position sensor will show up in a number of ways. The worst-case scenario is that there is no spark in the combustion chamber. Other symptoms related to the position sensor can include excessively long cranking time when starting cold, rough running on an intermittent basis, poor idle, stumbling or hesitation, a drop in mileage and stalling upon acceleration. These position sensor trouble symptoms may also be caused by a failure in the wiring of the sensor."

The things in bold are all things my car experiences sometimes.

[t.mcginley.jr]

Those are your Valve Timing Control (VTC) solenoids, basically used for variable valve timing, not your cam position sensor. Most of those conditions you mentioned can be cause by a bad coolant temp sensor, the wrong or old spark plugs, bad O2 sensors, dirty MAF, uncalibrated TPS sensor, etc. mostly just maintenance stuff due to age.

The VTC solenoids will eventually leak oil, however, so that may be one of your leaks. They basically just get sealed with silicone RTV on the bottom half against the head and a little bit on top against the valve cover (intake valve covers gets a rubber gasket, but still needs a drop of RTV in the corners).

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ok, I'll look into everything mentioned. I already replaced the spark plugs and bad O2 sensors. So if I am reading this right, I should just be able to seal up the VTC solenoids instead of replacing them correct?

[t.mcginley.jr]

Yes you can just reseal them with some sensor-safe RTV, they don't normally go bad. However, they won't come out without removing the valve cover, and to get the valve cover off you need to pull the upper intake plenum (which is a JOB, especially the first time you do it)

http://tech.aus300zx.com/Rear_Water_Hos ... ement.html

As for the weird running conditions, I would replace the coolant temp. sensor as my next step. They are only ~$20 and when they go bad it causes all kinds of weird problems, i.e. hard starting, poor idle and acceleration, terrible gas mileage, etc.

http://www.z1motorsports.com/product_in ... ts_id=1723

And here's a link for calibrating your TPS if you haven't done so already:

http://www.twinturbo.net/nissan/300zx/f ... ensor.html

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Thank you so much, I'll do these as soon as possible and let you know how it goes. Lucky for my I have removed the upper intake plenum twice in the in the last 3 months so I know how much of a pain it is, but at least I know I can do it. going to go pick up a coolant temp sensor during lunch and try to calibrate my TPS tomorrow since I have the day off. Wish me luck.

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I got the coolant temp sensor and it seems to have helped a bit. Still looking for a new power steering rack, no one around here seems to have any. As for the rest of this project, I think I will have to put it on hold for a couple weeks. But I'll certainly let you know how it goes once its done if you want to check back a while from now.

[solaire]

You sure that leak isnt from the valve cover over the VTC solenoid? The rubber in the v/c gasket will turn to plastic with age and heat and eventually won't seal. Looks by the pic tho that yours is pretty clean but it could be coming from the edges. My car (surprisingly) is leaking oil from the driver side looked like a VTC solenoid but it's actually coming from the plug on the back of the head.

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Yep, I'm sure, I completely replaced all the valve covers. My oil leak was really bad at first, to the point were I couldn't drive the car more than a mile or two. I bought a valve cover gasket kit from Z1motorsports and it fixed that problem. But, you could possibly be right, I may have missed something. The small drip that I saw was hardly noticeable, it would drip once every maybe 15 minutes or so and it hasn't caused any smoke. I just want to fix it because it is leaking and I don't want it to become a bigger problem. But I'll double check the valve cover and let you know what I find.

[solaire]

Does it drip with the car off? If not that's usually rear main. I replaced my oil pan lip seals and valve covers and still need to do rear main but I want to put a jwt clutch and flywheel when I do.

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I don't see any dripping when the car is off. I'll definitely add the rear main to my list of things to check. I'm hoping to be able to work on the car some more around the middle of next week.

[Schneidy95]

my Z was doing the same thing. Oil leaks out of the rear main, drips onto the heat shield around the stock down pipe, and smolders in there. (between exhaust and heat shield).

[t.mcginley.jr]

Old worn out PCV valves can also cause the RMS to leak, or leak worse if it was already leaking, due to not relieving pressure in the crankcase.

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Alright, finally got some time to work on this project again. I'm going to start working on it this weekend. I'll try to have at least the VTC solenoids done and check the MAF to see if it's dirty or not. I'll check in as soon as I can and let you know what progress I make.

[300zxstanced]

I have the same issue, I have a puff of blue smoke that once in a while makes by my shifter (smeels like oil). I have a new rear main seal, and pcv valves so im leaning towards the oil lines to the turbos, i am going to try and find it this weekend, if i can find it i will post my findings.

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Hello again everyone, I finally got the time to mess around under the hood again. I discovered that the VTC solenoid is really beat up. So I ordered a new one and it should be here by Friday! So besides my smoking problem, do you think this would solve any of the other problems I listed previously? If not that's fine, I can always make a new thread for a solution if I can't find what I'm looking for in the forums.

Thanks again everyone for your help so far, it is greatly appreciated.

[richardwait93]

@t.mcginley.jr do you know where the camshaft position sensor is on the vg30de? or does it even have one? i can't seem to find it

[evildky]

Please use Dexron type ATF in your power steering! Nissan has used this for years in power steering and many people still try using regular power steering fluid, the ATF is still a hydraulic fluid but with a higher heat range, and a bit thicker among other technical specifications. using power steering fluid will make a small leak worse and leak out faster.