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Black smoke and gas smell
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ilyes
New User
Oct 17, 2022, 3:55 PM
Post #1 of 10
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Black smoke and gas smell
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I have a Fiat Punto mk2 from 2004 that has a petroleum engine 1.2L 60HP.
I have had an intermittent ignition coil problem where the car would start shaking when idle and when the engine is hot (when the fans start) for a brief moment and stops when I accelerate. The problem went unfixed for a month or two.
Last week I changed the faulty ignition coil and changed the spark plugs at the same time.
The same night I started smelling petroleum inside the car and from the tailpipe. I suspected loose sparks plugs so I removed them and found them fouled with carbon, I cleaned them, checked the gap again, put them back and made sure they are perfectly tight. But the problem remained.
The next day, the car started producing black smoke but not very visible. When the engine is idle, it is smalls puffs of black smoke that happen at regular intervals (maybe every half a second or a second) and in between the exhaust is clear. When I accelerate, there is a big puff of smoke and then the smoke stops completely until the car idles again or until I decelerate a lot and accelerate again.
When the car produces small puffs of black smoke, the engine "sputters" (is that the right word ?) at the same rate and then it seems like it wants to accelerate or stabilize and then it starts "sputtering" again but there are no loud noises or any alarming ones.
I also noticed that the acceleration is not as smooth, the car is hard to accelerate, and sometimes, when idle, the rpm goes high and stays high until I press the gas pedal and than remove my foot (while being in neutral). Most of the time, the rpm returns to normal but rarely it won't until I turn off and on the engine or until I drive for some distance.
The car also threw a bad O2 sensor error code and although I had it changed 9 months ago, I went ahead and changed it again. When I removed the old one, it was fouled with a lot of carbon.
After changing the O2 sensor, the smoke stopped for 2 days but the fuel smell remained. Now the black smoke is back again and there are no error codes at all.
There is also a strong gas smell in the oil dip.
Is it possible that the new spark plugs are faulty ? It also came to my mind that I haven't changed the oil for 14 000 kilometers. Could this be the issue ? Honestly, I have no clue where to go from here, all I know is I have a rich fuel mixture and it could be anything but without codes it is so hard to diagnose. I'm even thinking the catalytic converter since the car has a mileage of about 200 000 kilometers.
Any help would be appreciated.
(This post was edited by ilyes on Oct 17, 2022, 3:55 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 17, 2022, 4:12 PM
Post #2 of 10
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Re: Black smoke and gas smell
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This car isn't sold to the US where site is doesn't matter. If that much odor and black it has uncontrolled fuel trying to burn fully and isn't obviously.
1st - check oil level for being too full and too thin diluted with "petrol" could be that and cause the symptoms.
This is dangerous of course and very damaging to converters.
So it needs help now no waiting code readings again it's dumping too much fuel clearly a list of reasons possible from faulty fuel injection or carb if it is long gone sold to the US.
Fire the big danger if this obvious don't let this stay another day you are wrecking this car's engine (likely) and more emissions parts.
Back to engine oil being too full it would splash inside and be too thin to lubricate engine.
Get on this even if you need pro help it can't stay this way up to not be driven till found and fixed also test out this engine if too full reading for oil check for damage low compression if so would be wearing itself out fast,
Tom
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 17, 2022, 10:00 PM
Post #4 of 10
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Re: Black smoke and gas smell
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ilyes: You said you checked plugs so seeing ONE fouled, others not is your clue - if so, which one?
Pay attention plugs tell a story.
By the way - cleaning plugs is out of date but can help for the moment and work - heat - not brushing them.
Vacuum leaks - anywhere can be hose or gaskets fools the engine it is under load when it isn't dumps too much fuel. There are a several reasons so need to know codes to help not tell you what is wrong rather where to look next.
Since you found an O2 sensor carboned up it should be warning you with a blinking engine light it's harming this thing. Hope you have time to avoid very dangerous and costly fixes unburned fuel if only in exhaust you'd smell but also makes a converter red hot till it kills it doubt this car can heat shield that much to interior of car??
Already suggested get right on this, you have the warnings from here don't get hurt over it scares me time flyting by this is near a 20 year old car things happen that might be small deals at first now has to be damaging the engine and or converter lost already they cost a fortune alone AFTER the fix don't wreck it again,
Tom
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ilyes
New User
Oct 18, 2022, 2:22 AM
Post #5 of 10
(3884 views)
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Re: Black smoke and gas smell
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Thank you for you help.
All four plugs were fouled. Not just one.I cleaned them because they are only 1 week old.
The fact that all four were fouled made me think toward either a fuel problem (fuel pressure regulator, fuel injectors) or an air problem (o2 sensors, map sensor) or a failed catalytic converter.
But the options are so many and I don't know how to go forward.
Today, I tried unplugging the HT leads one by one while the engine is running doubting one of the new spark plugs could be bad out of the box, but what I found seems weird to me : the engine keeps running at the same pace with just 3 plugs no matter which one I unplug. Isn't it supposed to shake a lot when I remove one of the cables ? That what used to happen in another car of mine.
Regarding vacuum leaks, I thought it was the opposite way, that there would be too much undetected air and not enough fuel therefore causing a lean mixture ? Did I have the wrong information ?
I'm keeping the car in the garage, just drive it to run tests, no more.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 18, 2022, 3:05 AM
Post #6 of 10
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Re: Black smoke and gas smell
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Re cleaning plugs: You didn't say how you did that. Use heat - just a good running engine is self cleaning them all the time. If a wire brush you make them easier to grab debris.
Lots of guessing till more it known I still want the oil checked or can give this up for lost cause soon!
IDK what sensors are ruling this show of dumping fuel low vacuum here would think it wants more another place less to be just right all the time - any temp of engine so it's adjusting all the time.
Back to plugs. 1 week old they'd clean with propane torch some other issues a toaster oven! Wet with fuel plugs misfire many don't dry out by air dry enough.
This is likely ONE issue making lots more troubles so much extra fuel not surprised it runs OK for a while with one canceled.
Said when you came we are US based this problem is universal IMO is an engine dumping extra fuel - barely matters what it is that has to stop,
Tom
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 18, 2022, 4:21 AM
Post #7 of 10
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Re: Black smoke and gas smell
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NEVER brush a spark plug. That leaves a metal coating that give spark a path to ground that prevents it from firing.
0/2 sensors and Catalytic converters do not cause problems. They get damaged as the result of problems.
You have excess fuel getting to the cylinders and you have to find out why.
If it has a vacuum fuel regulator the internal diaphragm can rupture and it will suck fuel into the vacuum line. If the fuel pressure is too high it will also cause a rich mixture
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ilyes
New User
Oct 18, 2022, 4:43 AM
Post #8 of 10
(3865 views)
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Re: Black smoke and gas smell
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I just changed the oil, the oil filter and the air filter (1 hour ago)
The car responds quite better to acceleration but there is still petroleum smell and black smoke from the exhaust.
The smell comes definitely from the exhaust tailpipe and there is also the same smell under the car but it could be the exhaust fumes coming forward because of the wind but no matter how hard I stick my nose, there is NO fuel smell under the hood.
The car doesn't have a vacuum regulator. The car electric sensors and regulators as far as I know are the fuel pressure regulator (part of the fuel pump system, NOT on the fuel rail, it has a returnless system apparently), a MAP sensor, two O2 sensors, an ICV, a throttle position sensor, a crank position sensor, a coolant temperature sensor, a speedometer sensor and an oil pressure switch.
Regarding the spark plugs, the deposits were quite easy to remove since they were quite hot when I removed them, I just used a dry clean rag and all the soot was gone.
The reason I came to the forum is because I already wasted a lot of money with electricians trying to diagnose the problem with just error codes and being clueless if there aren't any anymore. I changed an O2 sensor which I was sure was good but they insisted on not doing anything else until I change it. Now they say the engine must have overheated and that I didn't notice which is ridiculous and their reasoning is that if it was an electric device problem, there should be a check engine light or an error code !!
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Tom Greenleaf
Ultimate Carjunky
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Oct 18, 2022, 4:52 AM
Post #9 of 10
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Re: Black smoke and gas smell
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For the second changing oil was good. Now to find out WHY it's over fueling.
Said there's a list of reasons is why there are pro mechanics to help you out there this type web site format is not like being there in person - can't compete with that if you don't stubble on the real reason an engine in whole is in the risk!
Tom
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 18, 2022, 4:53 AM
Post #10 of 10
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Re: Black smoke and gas smell
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As you were told in the beginning we don't have that car here in the US so we have no specific info on the car. You were asked twice to test the fuel pressure but you have not done that. We have reached the limit of the help we can give you and it's time for you to take it to a competent shop, not the one you were dealing with.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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