I have a 2003 350z Touring Manual with 70,000 Miles on it.





Had it for about 2 years now and runs beautiful. Beside of the resent issues. A few months ago I noticed an increase usage in oil consumption, until one day I had a check engine light which was a random cylinder misfire. So I pulled my spark plugs and found this.





At this point I brought it to a tuning shop, and had a compression and leak down test done, which turned out good cylinder 4 had a 3% pressure loss. We also changed around the coils and got the injectors cleaned. But to no avail it was still consuming and fouling cylinder 4. Still drives like a charm though. The car was also smoking a bit blue on start up after sitting for awhile.

So at this point we were thinking it was in the valve stems. we changed basically all the seals and valve stems, except for the head gasket. Also note coolant levels were perfect. When the shop was inspecting the heads they found my chain tensioners were broken.





The valve seals were mildly worn but they were expecting it to be much worse. After all that was done the car no longer smoked as near as much.
A few weeks later i pulled the spark plug in cylinder 4 to inspect it and it looked like this.





Looked better but not as good as my other spark plugs.

A month or 2 goes by and i start to notice my oil consumption is increasing very rapidly. when i start my car after it has been siting for awhile it will some times burn blue smoke mildly. I pulled cylinder 4 spark plug again and it looked much worse then before, I forgot to take a picture of it, but it looked like things were growing off of it. Its burning about 1 liter per 800 Km. Right now i switched my oil from Mobile 1 5/30 to Amsoil 10/40 to see if will make any difference. We are kinda pussled on what the issue could be. Is it possible for it to be leaking oil at the piston even though I have perfect compression. Some people I have talked to say it can, and some say it cant. Thanks for the help Guys

The car still runs beautifully though, and at this point I think ill just have to live with the oil consumption until i can afford to have it rebuilt.

 

That is a huge problem with Z's made from 2003-2005 I fixed my problem took off the Valve covers used some washers with some heat silicone problem fixed saved over 800.00 bucks didn't have to buy new covers. That only thing I will say Is I had to take car into nissan to get it into the re learn process. cost my total 250.00 with taking into nissan

 

I had the valve covers replaced. Are you saying its still possible for them to be leaking, or is that just a way to fix it without replacing them.

 

Wierd to say the least. 3 percent wouldnt normally be a cause for alarm. When I see the white plug and you say the oil was minimized until recently I think that cylinder is running lean for whatever reason. Cracked piston or rings would turn up in a compression test. you can try the old check compression and then put a cap of oil and check it again. If it goes up usually lets you know of a ring problem.

With all the info you have this is one of the wierdest stories I've heard.

 

Worn oil control rings.

 

can you explain "check compression and then put a cap of oil and check it again" Little confused sorry.

 

Thats what im thinking, but my tuner is puzzled on it.

 

Unfortunately, compression test doesn't tell you anything about oil rings, so yes, it's possible to have good compression test and still oil consumption around pistons.

 

Check the compression. Lets say its 185, just for an easy number. Then take the tool out. Take a quart of oil and put a capfull of oil into the combustion chamber. Check the compression again. If it raises by a significant amount it usually points to a piston ring problem. The oil creates a temporary seal and will raise the compression a bit. If it doesn't raise and the compression number is low the only thing left is a valve problem.

 

Would it be worth trying this even though my compression is 3% loss.

 

I dug the spark plug out of the garbage when I changed my oil recently this is what it looked like.

 

I was puzzled why my z consumed oil and i called a buddy up that has some experience with them and he had told me that oil consumption in 03-05 was quite common if your driving in the higher rpm's. also i thought white plugs ment you were burning coolant or an extremly lean burn???? i know this dosent really answeryour question but i have had all the tests done to mine with jackshit coming up wrong i burn a quart every 1500 miles...

 

Ya they do burn oil Normally. But mine is going through 3 Quarts in 1500 Miles, and the spark plug is covered in oil.

 

Did you ever find out what the problem was?

 

Im going to resurrect this thread.

I have not found the problem yet, I am now using about a liter a week (300-400 Miles)

A recent thing I have noticed, my check engine light came on which is expected every 3000 miles telling me my spark plug is corroded to hell. But after changing it I noticed a few days later on the freeway my check engine light flashed then turned off. This has happened 3 times in the past 2 weeks. The code is p0300 Random Misfire. So my conclusion before was bad oil ring in cylinder 4 causing my spark plug in cylinder 4 to corrode. But If I Just changed the spark plug, why did i get the code and why is it Random not just cylinder 4 misfire.

Another thing i thought of, if I am burning oil in cylinder 4 why do i get A ton of blue smoke out of both sides of my exhaust. I mean like a 15 foot trail when i start my car. Shouldn't it just be smoke from one side. My exhaust is stock so I don't think there is any link between the two sides any opinions on this?

Should i check the PVC valve and valve covers my self to see if they were done properly?

Thanks for all the help Guys.

 

Just thinking the exhaust probably mixes in the cat back. Would it be a good idea to take the cat back off and see if blue smoke only comes from one side?

 

Do you have true duals exhaust all the way from cats or stock exhaust which is 2 cats merged via y pipe which goes to a single resonator and then do your single inlet exhaust with dual tips. You will see the same thing in both tips since it is merged via y-pipe. Sounds like you could have solved your issue with a short block and specifically piston rings.


Stock on the left

 

For some reason i was thinking the stock exhaust was a true duel exhaust, my mistake. Right now I'm doing some research on what i should do. Right now the plan is


-Z1 Motorsports Stage 2 short block (stock compression)
-Z1 Motorsports Heads with HR Head gasket (Cant decide if i should just use my stock heads.)
-Cosworth Intake Plenum
-Air intake
-PPE Long tube headers
-Exhaust (either Nismo or Motordyne ShockWave TDX2)
-Osiris Tune.
-Rev up oil pump and water pump
-Clutch and flywheel
-cd009 Transmission
(Turbo kit in the future + supporting mods)

My power goals right now is 280 Whp and Capable of doing a turbo kit plus supporting mods for 500 whp

Any input on the build would be appreciated.

 

Stick with stock plenum for now and save your money. You will not see any gains if you are not going turbo right away. You can do headers but they really don't help much and would give you a benefit down the road.

Only things that I would do for sure is,

Plenum Spacer
New Shortblock with HR head gasket and rev up oil pump
New CD009
Clutch/Flywheel
Full exhaust replacing cats and all.

 

Traded in Zed for a newer 2008 350z. Could not find out why it was burning so much oil without talking the engine apart. https://my350z.com/forum/2003-2009-n...2008-350z.html