Stagea Missfire & Black Smoke Help!

[StageaBen]

I own an automatic 1999 dayz edition stagea it has the rb25det neo motor which I think makes it a second generation rb25det.

Starting from the beginning

The car developed a hesitation under boost

(The boost had been increased by the previous owner via a bleed valve but wasonly running around 10psi)

I had already been advised that although the level of boost should be ok a bleed valve alone with a standard ecu is likely to cause problems.

I turned the bleed valve off completely which brought the boost down to about 5-6psi and seemed to fix the problem.

After about a week the problem came back so i started to ask around and see what might be wrong.

I spoke a mechanic an auto electrician and a turbo diesel mechanic and they ALL told be it would be my coils.

The problem started to get worse and when hesitating the car would blow thick black smoke. So bad that it would dirty the whole back of may wagon.

Then my engine light came on and wouldn't go away.

So even though my coils looked perfect to me i replaced them all with new genuine ones from nissan. I also replaced the plugs with new ones from nissan for my model stagea.

I did the ecu reset (batery/brake light method)

Engine light went away but problems didn't

After about a week the engine light was back again so I hit the forums and found out how to bring up the fault codes.

The computer told me I had a faulty hot air sensor(sensor in your exhaust just after the turbo). I replaced that with a brand new nissan sensor.

Engine light is happy now but i'm still sad.

I thought it could be the air flow sensor so i pulled it out and cleaned it with break cleaner but it didn't change anything.

Thats where i am up to now.

I can drive around fine as long as i stay below 0.2 bar!!!

So if the turbo spools at all I start blowing smoke and my power drops to the point where the car stutters and slows till the boost drops.

coincidently it also seems to happen if i go over about 2500rpm which is about when i start to make boost.

Any advise you guys could give would be a huge help.

I can't afford to just keep putting brand new parts in my car.

Edited February 19, 2010 by StageaBen

[nicr4wks]

Boost leak? could be a clamp come loose, split joiner, joiner popping off, etc.

[Duncan]

yeah I agree....might have been other issues before but what you are describing now sounds like a big boost leak. Check your hoses for splits because that would explain why it has been getting worse over time

[mad082]

+1 for boost leak. and a big one by the sounds of it.

[scotty nm35]

Do a search for the airflow meter dry solder joint issue, could be the pins loose in the afm board. If you can borrow a known good airflow meter and test it, that will rule it out as the issue.

The ecu is seeing more airflow than is getting into the engine so its running rich, could be the pipes but a leak that big should make quite a racket.

[StageaBen]

Thanks for all the help guys

I've looked/listened for leeks at idle but non are obvious.

I do have a vacume guage fitted so if i new what vacume my car is supposed to have at idle i could test it that way.

I pulled apart my air flow sensor and re soldered the all the "problem" spots but it didn't make any difference.

I tried reving the car in park and it revs happily to 4-5k(no point thrashing it) which it wont do under load as it generates boost well before then.

This leads me to agree that its prob a boost leek.

So i guess now i'll have a look around the forums and see if i can find a good way to test for boost leek.