Thread: black smoke and misfiring

hi all,

i have a 93 sentra se-r that's always had a problem with passing smog but i always managed to get it passed (barely!). it overheated on the freeway one day and i had the engine and radiator replaced with another sr20de from an infiniti G20. it was running fine after that, but then refused to pass its next smog and many parts were swapped to test. it sat for a while since i got fed up.

so one day semi-recently i started up after it was sitting for a few months and was misfiring badly with plumes of blue smoke coming out. the plugs were drenched in oil and had varying levels of black dust on them. got some new plugs and compression checked out ok (180 across the board). after running a while and replacing the MAF from a DET engine, the blue smoke slowly went away but running rich and now has black smoke. new #3 plug at first was only black on one half, but after a while got black all around. #1 plug also was black quickly, the other two took time to catch up. it consistently misfires still both at idle and while accelerating. seems better above 4k rpm but maybe it's just harder to tell. otherwise power seems ok. sounds like a diesel truck right now at idle and at lower rpms.

anyone know what's going on???

fyi, it's got bolt-on headers, a cone intake, and a larger exhaust.

any advice / help is appreciated!

maybe one of your injectors is stuck open?

btw here's a video of the black smoke:

http://img607.imageshack.us/img607/2959/2u6t.mp4

and pics...

plug #1


plug #2


plug #3


plug #4

Sounds like injector issues to me... Or some type of fuel delivery problem.

Check the orings on the fuel rail, remove the fuel rail from the manifold and prime it, if it doesn't leak then o rings are fine. Injectors could be stuck at that point.

Also check your distributor cap and rotor, if they are worn you are not getting a strong spark, thus the plugs would foul up like that.

I'll check that out. do you think it could be the MAF as well (since it's not exactly the same -- pulled from a DET). btw the ecu is original. it wasn't replaced when the engine was replaced.

also fyi those plugs had maybe 2 miles on them, 3 miles tops. it's hard to tell from those pics but even though #3 is completely black, two of the other three are varying levels of gray, and the other one came out pretty clean.

You're using a DET MAF? Yes, that could be the problem...
Either way, yes the MAF could potentially cause this. Although all plugs should look the same if the MAF were at fault.

You need to put the correct DE maf on there, and you also need to check your O rings on your fuel injectors like Vadim said, especially if the misfire goes away at higher RPMs. If you find that you do have a leaky O ring, just get OEM ones from Gspec.

my car was breaking up pretty bad between like 1500 and about 3000....my issue was a dirty maf....cleaned it and good to go

+1 on everything. sounds much more likely than the injector itself.

de maf != det maf?