ROUGH IDLE BLACK SMOKE WHEN ENGINES HOT

1993 Nissan Sentra

Tiny

CRisJOhn

July, 25, 2011 AT 10:37 AM

1993 nissan sentra
new fuel pump, distributor assembly
rough idle, black smoke when hot?

FOUND 740 RELATED QUESTIONS

Black Smoke Coming From Exhaust

65 ANSWERS
100 IMAGES

Smoking

32 ANSWERS
48 IMAGES

9 Answers

Tiny

mhpautos

July, 25, 2011 AT 1:35 PM

Check plugs and leads, sounds like a chronic misfire problem, pull plugs, faulty cylinder will have a very black and sooty plug.

Tiny

CRisJOhn

July, 26, 2011 AT 12:47 PM

Thank You for your responce.
New plugs, cap, rotor, wires, and fuel pump. Checked Mass Air Flow Sensor good. Recleaned plugs. Did Two Compression tests first one when Cold (1to4) 145psi. Did second when hot 1 and 4 was 85psi, then 2and3 was 115psi. Is this good or bad?

Tiny

mhpautos

July, 26, 2011 AT 12:51 PM

Do a wet test on the low cylinder, just a small squirt of oil to seal the rings, if the comp comes up it will be rings if not valves, do the test hot as well.

Tiny

CRisJOhn

July, 26, 2011 AT 12:55 PM

Thanx
Would the the two low readings cause all four plugs to have carbon build up? Thank you for rapid responce.

Tiny

mhpautos

July, 26, 2011 AT 1:01 PM

Normally not, but with 2 low comps we need to establish the cause of this, a problem with an inlet valve may impact on other cylinders. If you can do or get a leak down test done, this will isolate the main problem, such as which valve is leaking or if a ring problem.

Tiny

CRisJOhn

July, 26, 2011 AT 1:08 PM

Removed the fuel rail (with injectors connected) Turned on vehicle with out cranking over to check for any stuck opened injectors, was test good or bad?

Tiny

mhpautos

July, 26, 2011 AT 1:14 PM

You must find where the compression is going first, that type of test will be fairly inconsequential at this stage.

Tiny

CRisJOhn

July, 26, 2011 AT 1:19 PM

Thanx

Tiny

mhpautos

July, 26, 2011 AT 1:22 PM

It's near midnight here in Australia, so I am signing off soon, let me know how you get on. If you need more help re post here.

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