Rough idle black smoke when engines hot

Tiny
CRISJOHN
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  • 1993 NISSAN SENTRA
  • 4 CYL
  • 2WD
  • MANUAL
1993 nissan sentra
new fuel pump, distributor assembly
rough idle, black smoke when hot?
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Monday, July 25th, 2011 AT 10:37 AM

9 Replies

Tiny
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Check plugs and leads, sounds like a chronic misfire problem, pull plugs, faulty cylinder will have a very black and sooty plug.
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Monday, July 25th, 2011 AT 1:35 PM
Tiny
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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?
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Tuesday, July 26th, 2011 AT 12:47 PM
Tiny
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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.
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Tuesday, July 26th, 2011 AT 12:51 PM
Tiny
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Thanx
Would the the two low readings cause all four plugs to have carbon build up? Thank you for rapid responce.
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Tuesday, July 26th, 2011 AT 12:55 PM
Tiny
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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.
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Tuesday, July 26th, 2011 AT 1:01 PM
Tiny
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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?
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Tuesday, July 26th, 2011 AT 1:08 PM
Tiny
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You must find where the compression is going first, that type of test will be fairly inconsequential at this stage.
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Tuesday, July 26th, 2011 AT 1:14 PM
Tiny
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Thanx
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Tuesday, July 26th, 2011 AT 1:19 PM
Tiny
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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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Tuesday, July 26th, 2011 AT 1:22 PM

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