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Rough Idle, Check Engine Light, Gas Smell

13K views 14 replies 5 participants last post by  Zenzak 
#1 ·
Hello,

First thread for me and this is unfortunately to talk about an issue with my car.

Since yesterday evening, I have the Check engine light that came on my dashboard.

The car is shaking when idling, it smells gasoline a lot around the car and I can hear a knocking sound coming from the engine.

I only did 1 mile since it happened to go to autozone get the defect code checked, the guy showed me : Misfire Cylinder 4 (P304 if I remember well)

He told me it was either my spark plug or my coil, since I changed all 8 spark plugs a few months ago (no more than 4-5000 miles ago), I went ahead and bought a new coil but after replacing it, it still does exactly the same.

I plan on bringing my car to the garage tomorrow but if anyone has an idea, I will take it.

Here is a video, the knocking sound is very obvious at the end of the video :



Thank you for your help !
 
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#2 ·
Did you pull the #4 plug to check it?
 
#3 ·
I was not able to do it, I don't have the right socket for this, I will buy the socket tomorrow and try to do it before bringing it to the garage.

Just to give some more info, I am a bit overdue on my oil change (3300 miles), I was planning to do it before the end of the month (I drive 500 to 600 miles a month) and I am currently a bit low on fuel (about 1/8th of the tank).
 
#6 ·
Coulb be but since there is a very obvious gas smell around the car when the engine is on I think gas is still being injected in the engine.

I try to not drive the car at all in order to not break/melt my catalytic converter brick.

The gas smell suggests that there's an ignition misfire causing the engine to run excessively rich.
Check the plugs. At least one of them may have been contaminated by overenthusiastic use of nickel anti-seize compound.
I will do this during my lunch break, I will buy a new plug and replace the cylinder 4 spark plug.

The knocking noise that can be heard in the video I posted isn't alarming for you ?
 
#5 ·
The gas smell suggests that there's an ignition misfire causing the engine to run excessively rich.
Check the plugs. At least one of them may have been contaminated by overenthusiastic use of nickel anti-seize compound.
 
#9 ·
OK, so I changed the spark plug and I did not change anything, I was disappointed and ready to bring it to the garage but I decided to change both the coil and the plug to be sure and the car is now working fine.

The knocking noise is not here anymore but I still have the check engine light, is is supposed to come off by itself ?

I just unplugged my battery to make it come off and I will see if it comes back.

thank you for your help guys !
 
#13 ·
OK, so I changed the spark plug and I did not change anything, I was disappointed and ready to bring it to the garage but I decided to change both the coil and the plug to be sure and the car is now working fine.
I'm glad you've got it sorted out but what confounded me is that according to your original post, you'd already changed the coil so I can only assume that the first new coil was a dud.
 
#10 ·
Good to hear! The CEL will clear itself after a few on/off cycles or you can have Autozone clear it for you. Although I do think disconnecting the battery for 30 min+ will reset it too, but the computer will have to go through the "relearn" procedure, so the car may seem like its not acting the same until it relearns your driving habits.
 
#11 ·
The light will go off the second the battery is disconnected. It won't run any noticeably different while it "re-learns." If there is still a problem present the light will come back on either immediately after starting the car or after X amount of miles.


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