Smoke On Overrun

[waxer52]

Smokey, Misfire (valve stem seals maybe)

I have a rebuilt rb30 bottom end with new rings and bearings. New standard head gasket and an rb25det head.

I have got a misfire from idle and it struggles as you accelerate gently (wideband reads lean as expected due to misfire).

My crankcase breather is just venting to air at the moment with very little smoke at idle, but if I kink this pipe I get excessive smoke from the exhaust on deceleration. It still smokes a bit a idle from the exhaust.

The smoke is more white than anything, but has a slight smell of oil.

I have done the usual search and come to the conclusion its the valve stem seals.

Am I right?

Can bad valve stem seals cause a misfire?

P.s. I have wasted spark running perfectly, fuel pressure and injectors are ok, afm is ok.

[SECURITY]

connect your crankcase breather asap to see if it stops it THEN see if you still have a problem THEN we can start ruling things out. common sense would tell you to connect anything thats supposed to be connected to see if its causing the problem, and i dont mean blocking it off... connect it as standard.

its happened before - dysfunctional PCV has caused an oil problem on other cars including my own. start from there.

Edited December 10, 2009 by SECURITY

[waxer52]

Thanks

I read about what happened when you had your pcv bolcked off.

[waxer52]

Fixed it, replaced my pcv system and no more smoke.

The only other problem is the misfire I cannot find. Its not consistent it just comes and goes every couple of seconds.

Any help with this problem appreciated.

[SECURITY]

need more info. RPM it happens at? spark plugs and gap are you running?

either way it could be coil packs, spark plugs or CAS. re-gap plugs with a .8mm gap if you havent already.

[gotRICE?]

SECURITY saved my life with the same situation!

Stock RB25, catch can setup with blocked PCV, would smoke just after start up when i took off from lights, and came to a stop.

Reconnected PCV, never seen another whiff

Defiantly never blocking the PCV again.

[waxer52]

Im running msd coils in wasted spark mode. Cas has been replaced. Plugs at 0.8.

Misfire happens from startup most of the way up the rev range have not taken the revs over 4000rpm as mototr has only been built and not mapped yet.

[gotRICE?]

What ECU? Not having it mapped cant be helping?

How much boost? I would have thought with a strong spark youd be better off running 1.1 gap.

What about AFM? Tried a friends? Clean it? Plug connected ok?

[waxer52]

Afm has been cleaned, new plugs tried with different gaps.

Pfc with datalogit and wideband and no boost yet. Next step I think is to get a z32 and see what happens.

[SECURITY]

what about your ignitor pack?

[waxer52]

I have tested it but i have not changed it with another one. I will try that first to see if it works.