Car ran fine as I left the house yesterday but after about 1km got a CEL light flashing and shortly thereafter came a serious reduction in power. Turned around and got it home

Picked up an OBD reader and it shows misfires on cylinders 1,3,5 and 6

Guess its not a good idea to try and drive it to the indy so need to flatbed tomorrow morning

I am thinking coils. My indy told me before my last tech inspection that one was looking suspect but unlikely all 4 went at the same time?

 

I'd be more inclined to suspect fuel.
Car in your sig? 2006?

 

Did you leave the car outside or wash it recently? How fresh is the gas?

Marginal coils can be sent over the edge from moisture from a damp/cold night, rain, wash water, or stale gasoline.

There can be other explanations for the misfires too other than coils but with one being suspect the odds are coils is it.

Get the car flat bedded to the shop and let the pro diagnosis and correct the issue.

 

How old is your battery?
And is your alternator charging strong?


Start with those 2 cheap/easy solutions.
I had this exact problem less than a month ago. A new battery fixed everything. (And cost much less than new coils.)

 

Yes its the 2006 C4S

The battery is at least 3 years old (ie I haven't changed it since I bought it) but could be the original. Would the battery really cause this?? No idea on the alternator but have not had any charging issues

The gas is no more than a week old and it was dry and clear (had the top down!!)

 

I got the same CEL codes, I looked it up online and everyone pointed me towards a new battery.
If you don't have enough electric juice, you get misfires.
A new battery solved the problem for me, and it was a simple fix. (Cheap too)


BTW - your battery should be dated. It will tell you when it was made. Most batteries are good for about 5 years. Cheap batteries can go in a couple years.

 

Well I guess I don't have much to lose by changing the battery. Do I then need to clear the codes before starting it?

 

The code will clear itself soon after battery install if that was the problem.
Or you can clear it once the battery is in, if the CEL never returns, success has been achieved.

This can be tested by attaching jumper cables to another (Running) car and seeing if the open loop mode disappears after a few minutes. But I hate jumper cables, they can cause problems of their own

 

Put a new battery in and still got the CEL and car is running rough

Now only have a misfire code on cylinder 6. Is that the one on the drivers side farthest to the rear? that's the one the indy said was going

 

Well 5 out of 6 aint bad.
So how old was the battery?

The next cheapest solution to check is new spark plugs, and make sure the wires running to the coils are good.


BTW - sometimes this does take a while to sort itself out and the CEL goes away. But if your mechanic mentioned a bad coil, then it may be time to grab some new coils. I am glad the battery helped, but sorry it didn't cure the problem.

 

there wasn't a date on it anywhere - I suspect I now have 2 fully functioning batteries.

rather than guess and continue to spend money am taking it to my indy tomorrow. its not running any better than it was yesterday when this happened

 

Your battery should have markings on the top, as well as a sticker on the side.
The sticker comes off easy, but to remove the top info requires some serious scrubbing. (Like a dealership detailing the engine with a steamer)

Anyway, a battery only has about 5 years of good use. So a new one was not a bad purchase.


Good luck, and keep us updated

 

First disconnect maf sensor and try to see with car runs well at idle with no misfires. Do not exceed 3500 rpm.
It is odd to see all cylinders misfirng at once on both banks.

 

Can't recall where I came across this so take it with a grain of salt until I can find my sources but a misfiring cylinder can affect adjacent cylinders.

Regardless if #6 is causing grief at the other cylinders, the #6 coil is causing grief at least at the #6 cylinder. If all the coils are original and have some miles/time on them I'd be tempted to replace all 6 of them. You can spend a lot more money and time doing them all separately vs. just doing them all at once.

 

This "new-battery-for-misfire" deal is rather bizarre. I'm trying to picture how an older battery that will still start the car just fine can cause a load on the charging system so severe that there's not enough voltage left to supply the coils properly...