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Topic
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Background
I’ve been monitoring my car the past few months and it seems like I may be running rich. Can you help me diagnose my issue? Please read and understand clearly before making suggestions. The car is a Honda Civic Hatchback 1996-2000 model and has ~93,000km on the clock (d16y4 non-vtec engine).I believe I may be running rich because:
– Fuel consumption has increased about 2-3lires per 100km (will do further testing to confirm)
– Spark plugs seems to have carbon deposits (not sure)
– Recently seen black smoke (small puff) when revved and black deposits spitting out. NOT BLUE. black from my understanding is fuel and blue is oil. I’m not exactly sure if the smoke goes away after the car is warmed up.
– Smell of strong fuel “sometimes” (I don’t think its rotten eggs like a bad head gasket is)I believe it IS NOT a head gasket issue because:
– Oil is not milky
– Coolant is clean
– No coolant or other fluids are lost or degrading quick
– Spark plug seem to have carbon deposits rather than oil on itI think my issues is within:
– The o2 sensor OR catalytic converter. Anyone know the life expectantly of these and when they should be replaced?I have tried
– Cleaning the MAP sensor
– Cleaned the throttle body
– Sealed exhaust flanges (no leaks)
– Cleaned air filter, replace oilI’m planning to do: (please advise)
1. Change o2 sensor
2. Change catalytic converter
3. Change spark plugs
Or should I do it the other way around?Dry Compression Test Results
– 180psi across all cylindersImage of spark plug and leads. Consistent across all FOUR.
Suggestions
Please provide any suggestions on what to do next? and help me understand if my diagnose of my car running rich is correct. I think it’s either one or the other but I may be wrong.
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Replies
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When did you replace the spark plugs last time. Is it just me, I think it looks fine if it was been used for a while now.
Don’t change the cat. If you’re not getting error codes, then the system thinks it’s working right, but by the look of the plugs, things are running rather rich.
You could try replacing the O2 sensor. Others have suggested that the cheaper generic O2 sensors are not very good, so maybe stick to an OEM one.
The best way to figure out if you are running rich is to hook up a scan tool and look at the fuel trim values.
Spark plugs would not cause your engine to run rich. Running rich means the engine is running with more fuel than is needed to keep the air/fuel ratio correct. Meaning, the extra fuel is outside the computer control. You need to be looking at the fuel delivery system, specifically the fuel injectors.
Many times the little pintles in the fuel injectors become gunked up and leak extra fuel into the cylinders. I would advise cleaning the fuel injectors with a tool that hooks up to an air compressor. Here is a video showing how to do it by Scott Kilmer (Kind of an eccentric guy as you will see.) Don’t get that stupid additive that goes into your gas tank, that doesn’t do squat.
In order to help diagnose the O2 sensors and the cat you need to be able to look at the live data of the O2 sensors and fuel trim values.
[quote=”rahuljones” post=83438]When did you replace the spark plugs last time. Is it just me, I think it looks fine if it was been used for a while now.[/quote]
According to the service manual from previous owner, about 20,000km ago (half of its life)
[quote=”grg8888″ post=83447]Don’t change the cat. If you’re not getting error codes, then the system thinks it’s working right, but by the look of the plugs, things are running rather rich.
[/quote]If deposits are coming out of the car, wouldn’t the cat be clogged up or be really dirty?
[quote=”grg8888″ post=83447]
You could try replacing the O2 sensor. Others have suggested that the cheaper generic O2 sensors are not very good, so maybe stick to an OEM one.
[/quote]I will do this. I’m thinking of DENSO, or NGK o2 sensor.
Should I do o2 sensor -> spark plugs -> cat?
[quote=”Xyius” post=83448]
In order to help diagnose the O2 sensors and the cat you need to be able to look at the live data of the O2 sensors and fuel trim values.[/quote]I’ve tried purchasing a OBD2 reader with a DLC adapter but it doesn’t seem to work. Can’t find a DLC reader, I’m not too sure if they are able to supply live data like an OBD2?
[quote=”Xyius” post=83448]you will see.) Don’t get that stupid additive that goes into your gas tank, that doesn’t do squat.[/quote]
I had a Pontiac with GM’s generic V6 and it had a steady miss. I took this to be a burned valve and was preparing to pull the heads. Before doing that I threw in a can of injector cleaner. The next time I checked the miss was gone and it stayed gone.
So, maybe this stuff doesn’t work all the time or maybe it doesn’t work often but I suggest it is worth a try.
Here is a picture of what it shoots out. It appears to happen when the engine is still cold and doesn’t seem to happen when it is at operating temperature and driven for awhile.
As for the smoke, it appears it doesn’t happen anymore.
Would this defiantly be a running rich issue?
One of the main products of combustion is water vapor. Until the exhaust is hot this water vapor can condense in the exhaust. My wife’s Pontiac with dual exhaust would make puddles on the garage floor in winter. Any carbon in the exhaust piping will suspend in the water. So, what you’re showing is not a sure sign of running rich.
[quote=”barneyb” post=83703]One of the main products of combustion is water vapor. Until the exhaust is hot this water vapor can condense in the exhaust. My wife’s Pontiac with dual exhaust would make puddles on the garage floor in winter. Any carbon in the exhaust piping will suspend in the water. So, what you’re showing is not a sure sign of running rich.[/quote]
If it is in Winter, it will seem reasonable. It is summer over here.
I also wrote in the initial post that:
– There is increase in fuel consumption
– I have strong fuel smell from the exhaust
– The condition of the spark plug seems like it is running rich (carbon deposits)
– And black smoke but has gone away nowWell, if you don’t want to take it to someone with a scan tool there’s four things you can do. But, before you start, first off to Ebay for a copy of the shop manual. Then test the coolant temperature sensor for correct output. Next, check that the oxygen sensor is working as it should. You need to be careful when checking a heated oxygen sensor since two of the pins in the plug need battery voltage for the heater. I once managed to get a black face from creating a short when doing this. Eric has a video on this. Third, figure a way of measuring fuel pressure. How much fuel is injected is directly related to pressure. Finally, either pull the injectors and send them off for testing or replace with new.
Start with the easy and obvious. Put new plugs in it. A weak spark can cause several issues. Start with that and go from there. After installing the plugs pour some good cleaner in the tank and then hit the highway for a couple hours of higher RPM driving. Unless the injectors are seriously clogged this method is a good and simple maintenance practice.
If its still running poorly I wouldn’t change another part until you can read the codes properly.
[quote=”JS” post=83754]Start with the easy and obvious. Put new plugs in it. A weak spark can cause several issues. Start with that and go from there.[/quote]
Yes I was thinking about doing this, but if the o2 sensor is dying- wouldn’t that mean the spark will build carbon again which means I would have to replace the spark plus twice?
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