black smoke from exaust

[yaman]

Here is the scenerio:
* 1990 jetta 1800cc fuel injection.
* Cold started, engine runs smooth before heat up
* Once temperature rise to normal, engine runs erratic and black smoke come out from exaust
* Replaced spark plugs, distributor cap, spark plug wires - no gain
* Opened air intake console(test run without air filter)- no gain
* Black carbon soot found in spark plugs and from exaust pipe

What will the possible causes? Hope someone will answer.
Thanks in advance.

 

[Willcan]

Clean your engine,lots of carbon inside.

 

[yaman]

Eh......I doubt, this happened all a sudden, the vehicle was running fine a day ago.
Sounds like the carbon was caused by rich gasoline mixture during explosion.
I pulled each spark wire out when the engine is running and they all had good spark

 

[月下独酌]

hoho, one of those sensors is out.

 

[yaman]

that make sense! hard to find which one.

 

[yaman]

I hope is not the computer module.... That costs a lot of pain (deep pocket)

 

[月下独酌]

no
not ECU
has to be sensor
either the one at intake or the one at exhaust
hoho
deep pockets means u have lots of money, btw

 

[月下独酌]

woah, 1800CC fuel injectors?
r u nuts, that's way too big...
or do you mean 1800CC engine.?

 

[yaman]

1800cc fuel injection engine, not injector
BTW I don't have deep pocket, but it will be very painful for the cost of the computer module

 

[qwer]

Oxygen Sensor

 

[yaman]

May be.......
What do you think? 黑哥.

 

[yaman]

The rev is around 800rpm, but not stable.
When I accelerate, it has a tendency of stalling,than rev go up.
I test run on the road, it give black smoke and no power. Also has tendency of stalling when pedal the gas.
I have a feeling of bad grounding.
Tomorrow I concentrate on ground wires.
It is hard to work outside with this cold windy condition.

 

[yaman]

I don't think so.

 

[功夫]

Easy stuffs :smokin:

 

[yaman]

Find the freaking problem. Use multi tester and find one ground wire lost continuty. Remove the nut that hold the eyelette and found wire metal part separated, but the crimp still holding firmly with the wire insulation. Solder back and recrimp the wire. Test run ok.Big relief! Now I can keep the money nice and warm in my wallet.
Thanks a lot for people who provide me those valuable information.