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Tailpipe black; Oil or rich fuel
Topic Started: Aug 28 2011, 09:58 PM (1,120 Views)
red92
Advanced Member
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I did a complete rebuild for a second time and the engine is smoot and strong but the tailpipe is black
and some soot is collecting on the back bumper.


I haven't replaced the oxygen sensor but it could be something else.

Suggestions?
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Memphis metro


Does your check engine light work and do you have a check engine light on now?
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Bigshane90


If I was a guessing man I'd say it's because our geos are bad about carbon buildup.
Maybe your getting moister in the exhaust and causing it to show up on your bumper.
Edited by Bigshane90, Aug 28 2011, 11:15 PM.
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red92
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No check engine light coming on but it does work
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todaugen


Have you broke in the new engine?
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96Geoman


red92
Aug 28 2011, 09:58 PM
I did a complete rebuild for a second time and the engine is smoot and strong but the tailpipe is black
and some soot is collecting on the back bumper.


I haven't replaced the oxygen sensor but it could be something else.

Suggestions?
What happened with the first rebuild?

Did something go wrong or was that a long time ago?
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Bad Bent
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Facetious Educated Donkey

Good questions. Did you install a fuse and get a code 12?
I got a code 13 yesterday and the CEL was not on. Can't get a good reading of the mV O2 sensor output on my cheap DVOM so it's time to replace a 20 year old O2 sensor just on principle. :-/

I would also look at that, the distributor/rotor, and the above questions. Might bump your timing up to 8o BTDC. Clean your engine grounds and the ground wire connections on the back of the intake manifold. You might check for errant spark around the plug/coil wires by spraying a mist of water/soap on them, briefly, an look for arcing.

EDIT: IF the ECM thinks the engine is cold it will run rich. Check the coolant hoses on the TB which should be as hot as radiator hoses and test your engine thermostat.
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Edited by Bad Bent, Sep 2 2011, 10:06 PM.
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starscream5000
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Got 70 MPG?

If its sooty, then its running rich. If you run your finger through it and it's oily... Well you'll have your answer.
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red92
Advanced Member
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The soot is dusty. It blew a headgasket on the first rebuild and overheated.

On the second rebuild I decided to leave the thermostat out since I'm in South Carolina and our days have continually been over 100 degrees.

I keep noticing talk about a meter reading.

Is there a meter that I can buy and if so where does it connect in my 90 and 92 Lsi convertibles.

I'm clueless in that department.

I think I'll pick up an o2 sensor and replace the old one. I think it's been in there for a long long time.
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Old Man


Re: Thermostat. It has been my experience that if you leave the thermostat out and drive for any extended length of time, especially in hot weather you will start over heating.

The thermostat opens when the water in the engine gets too warm. It stays open just long enough for cool water from the radiator to get in the engine, and makes the "too warm" water stay in the radiator. This gives the radiator a chance to cool the "too warm" water down.

If it just rushes through the radiator the "too warm" water will not cool down. Eventually all the water in your system will be "too warm" and the effects of no thermostat will be all too evident to you.
Edited by Old Man, Sep 8 2011, 08:14 PM.
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starscream5000
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Got 70 MPG?

The Old Man is right. Without a t-stat, the water will rush right through the radiator without having enough time to cool down. All of the coolant will eventually heat soak. The longer the trip, the worse it will be. If a t-stat isn't keeping your motor cool enough, then you probably have a blocked radiator the either needs to be cleaned out or replaced.
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red92
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The thermostat is going back in. Thanks!
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