Car one cylinder misfire

[DC Concours]

There are many of you that know engines far more than I ever will. I have a question for you guys...can driving a car that is misfiring on one cylinder damage the cylinder or the engine? The car is 25 years old, inline 6 and I suspect just needs fuel lines cleaned and Spark plugs replaced. I just won't have time to get to it till next week. Plugs last changed 10 yrs ago. But only driven about 30k since.

P0304 code. Twice cleared. Twice back.

[MrPepsi]

I believe it can cause issue with excess fuel in the cylinder. I think a mechanic would tell you not to drive it. I am not a mechanic though. Depends on how much you value the vehicle I guess.

[MrPepsi]

https://www.yourmechanic.com/article/is-it-safe-to-drive-with-a-misfiring-cylinder
Your Mechanic says no.

[m in sc]

you need to determine the cause. if its a port injected  motor, might be a bad injector. If it has coil on plug coils, might be a coil. could be a wire. but the days of plugs and 'clearing fuel lines' on anything fuel injected are pretty much over as a cure. I mean, its possible but rare and extremely unlikely.. if its smoking or the oil looks milky can be a head gasket.  could be a broken ring in the cyl. all sorts of causes are possible, but you need to get a legit mechanic to look at it. Not Meineke or AutoZone.  good luck w it.

what make of car and how many miles?

[DC Concours]

Thank you Mr. Pepsi. I like pepsi over coke as well. I read your link and he says not to drive!

Gentlemen, I wish you guys lived closer to me.

M in SC, the car is an old hand me down Mercedes inline 6. The obd2 is showing p0304. A misfire in cyl 4. Last time it happened, a long time ago, it was worn plugs. She did fill up at a new station and the rough idle and loss of power began soon afterwards. It may just be a coincidence. The plugs are oem copper and they are due for a change.

For now, assume it is just an old worn spark plug #4, is it going to cause damage driving highway miles for a week? The car idles bad, and has weak takeoff acceleration. But just fine at hwy speeds.

[Strawboss]

Washed my engine once and water collected in one of the plug wells and that plug did not spark hence the cylinder did not fire, ruined the catalytic converter by plugging it up with exhaust goop. It ran kinda ok after I replaced the plugs, but it did not pass the emissions check as the converter was junk. Don't drive it.

[m in sc]

interesting, im familiar with them. yeah might be water in the tank. def not good, try to thow a bottle of HEET in the gas tank, it will take care of any potential water and -maybe- the plug will clean off.  Id def get it sorted sooner than later. misfire can still be a coilpack or wire. however, whenever that plug gets pulled, take a good look at it. might be oil fouling again due to a head gasket issue. could be **** in the tank got stirred up and clogged that injector. 

[DC Concours]

Thanks guys. I'll update you on what I find. I was able to finally procure some copper OEM plugs. f8dc4 plugs are hard to come by locally.

[DC Concours]

Oh man. I shed a bunch of tears when I saw this. I opened the cover and my heart sank.

Immediately I see all this carbon dust (little grittier than soot) piled up around the coil, above cyl #4. Damn. These coils are expensive.

There was a pile of carbon inside the plug hole too. Damn! And the plug connector attached to coil was covered in carbon too. After I vacuumed it out and grabbed the plug.....The plug was loose!!! Damn. Damn. And the plug was broken too. DAMN. The plug's top terminal was melted to a slant and the copper core was loose sliding back and forth inside the plug! F@#K.

What the hell happened here?

See the pics here.

https://www.dropbox.com/sh/2x8sooydron1ega/AAC7PbUbb4JUnrJRqf8nmGZNa?dl=0

[zarticus]

You can buy coil over plug coils on Amazon for a fraction of what auto dealer or part stores charge. I changed all 4 coils on my wifes ford escape last week. part stores wanted $89 each for their cheapest, I bought 4 on Amazon for $28 for all 4. under 10 minutes to switch out and the car is running like new ! 

[Boomer]

See the pics here.
https://www.dropbox.com/sh/2x8sooydron1ega/AAC7PbUbb4JUnrJRqf8nmGZNa?dl=0

Dunno what file format you saved them as but I couldn't view them.
The most common cause of what you describe is that the plug cap/coil is not seated correctly onto the spark plug.
That is why they are almost always bolted down these days.
Not being correctly seated leads to a second gap between the cap and the plug.
The arc there eats away at the top of the plug and generates massive localised heat in that area which cooks plastics and rubber seals turning them to carbon dust. The misfire starts when the arc has eaten away enough of the plug so the gap gets too big to easily arc across.

[DC Concours]

Thanks for the explanation boomer.

The file format is straight from my iPhone— heic. It can take minute to render on your browser. It's proprietor APPL format. You should be able to see the images if you open the link in the newest Google Chrome or Firefox browser. Please let me know if it still doesn’t work I’d like for you guys to see the pictures. It looks awful.

[Boomer]

Work PC was blocking them. I can see them from my home PC.

Does not look like arc damage to me.
Looks like the cap/coil did not seal and dirt and water got in there.
The top of the spark plug is at a weird angle so that may have caused the poor seal by twisting the adapter.
I would clean all of the dirt out and replace all 6 sparkplugs.
That dirty rubber part just pulls off of the coil pack. It's just a different type of spark plug cap.
Each coil fires 2 plugs simultaneously, the one underneath it and the one that has a plug lead and cap.

[m in sc]

consider yourself lucky, that's an easy repair in the grand scheme of things. glad you found it. 

[DC Concours]

Thanks. I know these coils would be expensive but I searched online and found them for about 60 bucks  each. Nowhere close to your killer deal. I didn't know they still made them after 2 decades. I'm happy. In plan on changing out the plugs sticks coils and wires. I think that'll cost me some coin but the car is still a great city car.

You can buy coil over plug coils on Amazon for a fraction of what auto dealer or part stores charge. I changed all 4 coils on my wifes ford escape last week. part stores wanted $89 each for their cheapest, I bought 4 on Amazon for $28 for all 4. under 10 minutes to switch out and the car is running like new !

[DC Concours]

The top of the Plug that you see slightly bent is actually broken. It looks like a lot of heat was applied to the joint and it cracked.

I replaced all 6 plugs And cleaned up the sticks especially the dirty one. after I cleaned everything up things didn’t look too bad. It was 29° outside when I did this so I was in no shape to investigate any further. Normally I would have replaced that one coil but the coil looked clean didn’t have any burns on it. I plugged everything back and I’ve driven about 100mi. It seems to be running smoothly. Thus far.

Work PC was blocking them. I can see them from my home PC.

Does not look like arc damage to me.
Looks like the cap/coil did not seal and dirt and water got in there.
The top of the spark plug is at a weird angle so that may have caused the poor seal by twisting the adapter.
I would clean all of the dirt out and replace all 6 sparkplugs.
That dirty rubber part just pulls off of the coil pack. It's just a different type of spark plug cap.
Each coil fires 2 plugs simultaneously, the one underneath it and the one that has a plug lead and cap.

[DC Concours]

That’s true. Any repair under the valve cover would cost more than what the car is worth at this point. I’m surprised how the plug got loose under so much pressure. I guess I need to re-torque these plugs every couple of years.

consider yourself lucky, that's an easy repair in the grand scheme of things. glad you found it.