2006 Chevrolet Epica Smoke coming from exhaust pipe

Tiny
AB_ARCEO
  • MEMBER
  • 2006 CHEVROLET EPICA
  • 2.0L
  • 4 CYL
  • FWD
  • MANUAL
  • 378 MILES
After doing all types of repairs; overhauling (changed piston and ring) and replacement of defective 2nd oxygen sensor, heavy smoke stopped. My km/liter consumption has improved from 7.5 km/L to 9.25 km/L. The problem is when rev at 3,000 or more, visible black smoke is coming from the exhaust pipe. Have it scanned but no problem detected. What are the possible reasons? I don't know what to do with my car.
Thanks

P.S. My car is about 378,000 KM
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Tuesday, November 11th, 2014 AT 11:13 AM

7 Replies

Tiny
JOHNNYT73
  • EXPERT
Did you replace the valve seals when doing your overhaul?
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Tuesday, November 11th, 2014 AT 11:55 AM
Tiny
AB_ARCEO
  • MEMBER
About the valve seals, yes they were replaced during overhauling.
History:
Before the car has been scheduled for ovehauling, these are the signs:
1. When rev at higher acceleration, black smoke is coming from the exhaust and significant reduced in engine oil.
2. During idle, white-blue smoke was also there.
Right after overhauling and break-in at idle speed, no black smoke has been observed. But when accelerated, heavy cloud black smoke is there to the point that excess gas also mixed with engine oil leading to the busted spark plugs (heavily carbonized). Replaced the exhaust O2 sensor and the spark plugs. Heavy smoke has gone. What remains is little black smoke coming out from the tail pipe when highly accelerated, but no signs of failure detected from scanner.
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Wednesday, November 12th, 2014 AT 2:59 AM
Tiny
JOHNNYT73
  • EXPERT
When you plug in your scan tool. Scroll around and look at all your temperature values such as engine coolant temp sensor (ECT), intake air temp sensor (IAT), and ambient air temp sensor to make sure everything reads correctly.
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Wednesday, November 12th, 2014 AT 4:53 AM
Tiny
AB_ARCEO
  • MEMBER
Thank you sir.
I will do it as soon as I can and will inform you back.
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Wednesday, November 12th, 2014 AT 10:04 PM
Tiny
JOHNNYT73
  • EXPERT
Just checking in on your progress. Any luck with the issue?
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Sunday, November 16th, 2014 AT 12:36 PM
Tiny
AB_ARCEO
  • MEMBER
Sorry for the late reply.

Yes Sir, the coolant temperature sensor is at fault. Replaced it immediately and the slight black smoke coming from the tail pipe during high rev has tremendously gone.

Thank you very much, :)
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Monday, November 17th, 2014 AT 3:33 AM
Tiny
JOHNNYT73
  • EXPERT
Great! That's really what I was shooting for, but I wanted to make sure they were all in good working order. Happy to help!
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Monday, November 17th, 2014 AT 4:12 AM

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