My miata is going to die young
 

Finally breaking down and writing a thread about this. I've been testing, lurking, and searching for the answer to my BS problem. My 1.6 has decided to take up smoking(Blue) and I haven't had a lot of time to mess with it as it is my DD and I have numerous other projects I'm working on....

It smokes a bit when i start it, even more when revving. It smokes like five packs at once when I leave a stoplight. F-ing sucks. Can't tune the car at all right now as the O2 readings are off.
Btw, Specs are in Sig, also have Cometic head gasket, arp head studs, PNP head, new seals in head.

Here is what I have done:

Compression test = good. No huge change in between psi from cyl. to cyl.
Rebuilt my T25 with a kit from the G-pop shop
Plugged my pcv valve to test to see if I was getting alot of blow by, no luck.
Leakdown test (Cold) showed 15 on all cyls except 1 was at 20

Nothing has given me any clues.
Car has been frustrating me wayyyy too long.....:vash:

could be bad pcv, i dont think its a bad compressor seal though. How is your oil return routed? have you checked the pcv? The 02 sensor is most likely fouled with oil.

O2 has black soot on it, not wet with oil. Pcv has been pulled off the intake side, taped the intake manifold hole and it still smokes. B6t pcv anyways... Oil return is routed to the oil pan. Also leaking a bit of oil from the turbo....still investigating that, trying to see if it is from the oil feed, return or turbo itself....

Could be your intake or exhaust valve stem seals. Easiest way to check for that is to pull the intake and exhaust manifolds and have a look at the stems of the valves. If you see leaking (or a really 'wet' port), you have your answer.

Do you have a restrictor in the oil feed for the turbo?

compression and leakdown test.

you plugged your pcv valve? Is your other crankcase port on the exhaust side plugged as well?
if you plugged all your crankcase vents you will easily smoke as build up to much pressure inside the crankcase.

The other side has a breather on it. I only plugged the pcv to test.

Compression and leakdown has been done and numbers are good.

I don't have a restrictor in the oil feed. I think it doesn't need it because it is a t25 journal bearing turbo from a sr20det. I could be wrong though.

Valve stem seals have been replaced 5k ago, but I will check to see if they are leaking down to the top of the valves in a couple of days.

I don't know either, but when you mentioned leaking oil from the turbo it reminded me of my 'after 3 years needing a restrictor' moment:

https://www.miataturbo.net/diy-turbo-discussion-14/turbo-ruined-56181/

well if your turbo is leaking then it could be you burning off the residue as it hits your exhaust on the outside.

Spent some time clocking my turbo the other day as the drain wasn't straight down. Didn't seem to be make a difference. Im going to work on it more soon, just have to get my brothers P.O.S. civic out of my garage first.....

going through the same thing, with a few differences. mine smokes after overrun, as soon as i give it some gas. does not smoke (at least significantly) in the morning or on acceleration. probably a different cause, but my approach (in case it may help):

1. change the valve stem seals (mine are 21 years old :giggle:)
2. take of DP and WG and turbo and look at the turbine wheel. If lots of soot and oily and not generally clean, perhaps the rear turbo seal is leaking. Not entirely sure if oil will show there even if the rear seal is leaking, not sure if oil burns immediately due to high temps or not. but plan or running the car till it smokes, then shut if off and then look at the turbine wheel (Thanks Faeflora for the suggestion).

If all is ok, then it is only one other thing: the oil rings. But since these require opening the engine, I would like to look at them last.

There could be other things, but in your case (and mine) probably ruled out: insufficient draining along the turbo oil return line, too much oil pressure fed into the turbo (in which case a restrictor would be indicated), high blow by, etc.

Unfortunately, I don't think good compression AND good leak down helps at all in narrowing it down (I got 160 psi on all 4 and 1-3% leakdown on all 4). Meaning, if all checks out ok (your case and mine), then what? is it the valve seals? is it the oil rings? is the turbo fed too much oil? too much blowby? partially blocked oil return line? you can't tell them apart.

good luck and post updates.

This is most likely intake valve stem seals. You are sucking oil through them when you generate high vacuum. When you give it gas, the oil is there ready to burn.

Doesn't sound like OPs problem though.

I hope you are right. Will change the soon enough. Why don't i get any smoke in the morning?

UPDATE!

Ordered some supertech valve stem seals and installing them this weekend. Is there a way to check if it is the valve stem seals that are leaking vs. the valve guides themself (In the contact between the head and the guide, not the valve and the guide; or does that not generally happen?) Btw, if this works, I'll probably be so happy I'd punch a baby!