Mechanics

WILL A BAD FUEL INJECTOR CAUSE THE EXAUST TO BLOW HEAVY WHITE SMOKE AND SMELL LIKE GAS?

2000 Nissan Maxima • 230 miles

I start my car and it dont smoke real bad, but after a few minutes it gets smokier, if I step on gas it blows heavy white smoke out and leaves a puddle of gas by tail pipe.I also get a po300 code. New plugs and all coils checked also. All in all its not drivable cause theres so much smoke and gas goes down real fast.
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Michaels2000
March 10, 2012.




White smoke is a sign of a leaking head gasket. The coolant level should be going down too. Too much gas will cause black smoke and soot inside the end of the tail pipe.

Caradiodoc
Mar 10, 2012.
I just pulled all the plugs out and all are black carboned except for cylinder 6 which was clean and wet with gas the others where also dry.I checked for the antifreeze going down and no change and the exaust doesnt smell like its burning coolant.I found puddle thought it was water also till I put finger in it and smelled it, was gas : (

Tiny
Michaels2000
Mar 10, 2012.
Oh also the iol smells real gassy too.

Tiny
Michaels2000
Mar 10, 2012.
Oil lol

Tiny
Michaels2000
Mar 10, 2012.
The two observations don't really jive. Too much gas causes black smoke in the exhaust, and coolant causes white smoke.

You might try switching injector 6 with one from a different cylinder and the coil from cylinder 6 with the one from some other cylinder to see if the problem switches to one of those different cylinders. Resistance tests on coils only show if there is continuity. They don't tell if one is arcing internally from the high voltage.

Caradiodoc
Mar 10, 2012.
Ok well before the car started smoking real bad, I was getting a intermitting missfire when going down road and it would come and go for about a month. Then one day it didnt come out of it. Prior to this my cat converter was smelling real bad when I tromped on it.I also got an o2 sensor code and a cylinder 6 misfire code.I had to remove battery for a while too for winter, alternator was dead. So when I put battery back in the codes were obviously gone. But just the o2 code came back and the po300.I changed the o2 sensor that was bad and no change. Could the cat be the problem, maybe build up in it that is burning up when it warms up?This thing smokes so bad that it looks like cream coming out the back, then when you turn it off you can see smoke trickling out the tailpipe like it was liquid. Im totallt stumped.

Tiny
Michaels2000
Mar 10, 2012.
You're trying to fix the results, not the cause of the problem. A misfire, as detected by the computer, will put excessive raw fuel into the exhaust system where the catalytic converter is overwhelmed. It will overheat and smell like rotten eggs.

The oxygen sensor only reports what it sees. Changing it isn't going to solve anything. In fact, you can have an injector stuck open dumping way too much fuel, but the oxygen sensor can still read normal swings from rich to lean a couple of times per second like it's supposed to. It doesn't respond to unburned fuel, just unburned oxygen. As long as the other two cylinders on that bank are working properly, the oxygen sensor won't detect a problem.

Caradiodoc
Mar 10, 2012.
Ok that all makes sense. Then probably got a small leak in the head gasket and that is effecting the engine so the computer gets a reading that tells it to add too much fuel. That would explain why I smell gas along with the white smoke at the same time. Usually I start my car up and it dont smoke until it runs for maybe 3-5 mins. Then it gradually just gets heavier white smoke. Then if I step on it im in a smog cloud.I will have it checked for head gasket leak then. As you said if it was the fuel system it would be black smoke. Even if it was a bad coil it would still be black smoke correct?
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Tiny
Michaels2000
Mar 11, 2012.
Yup. The symptoms are contradictory. When a coil or plug misfires, the unburned mixture goes into the exhaust system. The unburned fuel should be mixed with stored oxygen in the catalytic converter, and burned so you shouldn't smell anything, ... Yet.

The oxygen sensor doesn't respond to unburned gas, just unburned oxygen. The computer is constantly varying the mixture from too rich to too lean a couple of times per second, (that's where the converter gets the oxygen to store momentarily). With that misfire, it sees that oxygen all the time and figures the average mixture is too lean, so it adds fuel to correct that. The problem is no matter how much fuel it adds, there will still always be that unburned oxygen being detected. THAT's when the converter gets overwhelmed and you smell unburned gas at the tail pipe. You smell gas, but he computer sees a lean condition and tries to add more gas. That's the contradiction.

Most V-type engines, '96 and newer have oxygen sensors on each half of the engine so a misfire in one cylinder results in fuel being added to all three or four cylinders on that side. Older engines usually had one oxygen sensor. A misfire ended up with fuel being added to all cylinders.

There's two possible explanations for why the smoke occurs well after start-up. The cylinder heads and gaskets expand when they get to normal operating temperature. It could be that's when a leak shows up. It's also possible for system pressure to cause coolant to seep into a cylinder after the engine is stopped. If it's excessive, that can cause "hydro-lock". Since liquids don't compress, that fluid can stop a moving piston and cause a no-start, (no crank) condition. If, on the other hand, a valve is open when you start cranking, the liquid can be pushed into the exhaust system where it will vaporize after the exhaust system gets hot. That will take a few minutes. Some of the coolant will spray out of the tail pipe right away as a liquid. It won't smoke until it gets hot. That liquid can collect in the muffler which takes longer to get hot enough to vaporize the coolant.

One problem with my analysis is: "i checked for the antifreeze going down and no change". With the amount of smoke you're describing, you should be losing a lot of coolant. Next, "i found puddle thought it was water also till I put finger in it and smelled it, was gas". We know something is going on with cylinder number 6 but gas won't wash it clean; coolant will. A better way to tell if gas is dripping from the tail pipe is to wait and see what happens to the puddle. Water will still be there an hour later but it can easily smell like gas if there was a little in it. Gas will evaporate in a matter of minutes and leave a stain on blacktop or concrete.

Caradiodoc
Mar 11, 2012.
Ok the stain on the ground is definatly happening. Leaves a dark stain in dirt in my drivway where I reved it up a few times noticed other day after many hours. And as far as the number 6 cyl issue probably where the leak is since all the other plugs are black with carbon probably cause of increase in fuel being added, and that #6 plug being clean cause of the coolant leak. Im gonna tear it down I guess, youre input has been very helpful. Thanks alot.

Tiny
Michaels2000
Mar 12, 2012.

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