90 Honda Accord smoking

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  #1  
Old 01-02-03, 08:16 AM
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90 Honda Accord smoking

I have a 90 Accord with about 135,000 miles on it. It runs very well and other then the jerky transmission shifts there are no problems with it. However, lately it has been starting to smoke fairly "hard" starting about 5 seconds after the car starts, and lasting about 1 minute or so. The smoke is kind of black/gray in color. I though it was oil, but it doesn't really smell like burned oil, it smell more like unburned gas. But I could be wrong. I haven't noticed any change in the way the car runs, or any drop in mileage. The car loses no antifreeze. Oil is another story as the oil pan gasket leaks, and there is no easy way for me to tell if the lost oil is burned, or it just "drips down". Any idea what the most likely cause is?
 
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  #2  
Old 01-02-03, 09:03 AM
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Usually oil burning is blue smoke, black smoke is usually over rich condition. Does it do it when engine is warm and turn off and then started, or does only smoke when the engine is completely cold? Might check make sure the air filter is not getting clogged.

Good Luck
Online2
 
  #3  
Old 01-02-03, 09:14 AM
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I only notice it when the engine is cold.
 
  #4  
Old 01-02-03, 10:47 AM
Joe_F
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When was the last time it was tuned up and gone through? Any trouble codes stored in the computer?

Start with "The Basics" below.
 
  #5  
Old 01-02-03, 11:41 AM
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Hi Joe,

The spark plugs along with the wires were changed about about 1 year ago. The car passed emmisions less then 3 months ago, and no value was even close to borderline. The car always "spew" black smoke when floored, but nothing significant. I'll take the plugs out this weekend and see if they are "fouled". It has Bosh platinums right now.
 
  #6  
Old 01-02-03, 05:22 PM
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Hello-
What you are experiencing is an open loop condition created by your oxygen sensor. At cold temperatures, your oxygen sensor reads the exhaust output and tells the ECU (computer) to use a more "rich" misture of air and fuel until the car is warmed up. In this case, your Oxygen sensor is telling it to use too much fuel and not enough air--thus the grey/black/white smoke. I doubt it's oil unless it's blue. You also said that it's black if you "floor" it.

My guess is that your oxygen sensor is bad and needs to be replaced; especially with that kind of mileage on your car. You can pick one up at Autozone or Pepboys for under $75. I would also invest the $40 in gaskets to repair the leaking oil pan gaskets.

Good luck!
Curt B. Shumaker
 
  #7  
Old 01-03-03, 01:09 AM
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RUN MODE
The run mode has two conditions called Open Loop and Closed Loop. When the engine is first started and engine speed is above 400 RPM, the system is in Open Loop operation. In Open Loop the PCM ignores the signal from the Heated Oxygen Sensor (HO2S), and calculates the air/fuel ratio based on inputs from the TP, ECT and Mass Air Flow (MAF) sensors.


Pull the error codes from the computer first. Black smoke is a rich mixture. Fuel delivery problem or weak spark. Oxygen sensor only comes into play after the engine warms up and the system goes closed loop.
 
  #8  
Old 01-03-03, 07:52 AM
Joe_F
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Thumbs up

I'm with Stevo. The O2 sensor has nothing to do with it until things are in closed loop. An O2 sensor SHOULD be changed as a maintenance item, as you will pick up some MPG by doing so and changing a lazy sensor.

The problem is elsewhere---you've gotten good advice from Stevo here. Start with the simple stuff first and go in order so as to not miss something simple.
 
  #9  
Old 01-03-03, 08:50 AM
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The computer has no error codes stored. The car runs great, and it will only put out dark smoke when the RPMs go above 4000 (even when revved in park). But it's always done this. The smoke that comes out right now is lighter in color (gray to dark gray), and it stops by itself after about 2 minutes. No more smoke after that. Since the car is running fine, and has no misses I'm hesistant to believe a tune-up will solve the problem. I'm more inclined to believe that worn valve seats/guides are the problem. If that's so should I have the heads re-done (if so, who can do this? I'll pull the head out myself), or should I just replace it with a "junkyard" head? If I do that I might as well replace the timing belt also (it's my mother's car, and my parents don't believe that a timing belt that will break can ruin the head (we'll see... )
 
  #10  
Old 01-03-03, 10:10 AM
Joe_F
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On older GMs, black smoke on demand like that would be a purge valve or MAP sensor type issue.

Both can be checked. Before dumping any green into changing parts and swapping heads, read up in Autolibrary.org below about the various sensors and how to check thm.
 
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