My car has been idling rough lately, it was very noticable at one point and the check engine light came on. I went to the dealer and ofcourse by that time the light was off, but they were able to grab the code from the ECU and it stated there was a mis-fire, but they cannot figure out why. My car has about 7800 miles and it still idles rough, but not as rough as when the light was on. I had the oil change and I always put SUPER gas in my car.

Anyone experience this and if so what was the cause and solution? Thanks!

 

More than likely, you may have a bad coil or a plug that is gone.

 

I appreciate your input but if this was the case then the Check Engine Light would be constantly on correct?
I would think so because this means that one of the cylinder is not getting a spark.

 

Bad coil is one that doesnt work 100% of the time, not necessarily dead. It could be that or a Bad Plug

 

Not if it's intermittent.

You also don't say if you have any mods or not.
If not it could also be an air or vac leak in either valve cover or intake track after the MAF.

A misfire isn't a cylinder that doesn't fire per se but one that fires at the wrong time, Usually related to a lean condition or bad fuel.

 

The only engine mod I have is a Franken WAI.
Let me know what you all think!

 

Check all the hose clamps. Sounds like you have a leak, letting air in beyond the MAF. This will cause rough idle and missfire because of poor fuel/air ratio. Since your only mod involves the intake, this is your best bet.

 

I understand and appreciate all of your input, however the intake has been on my car for about 8 months now without any problems.

 

Could've come loose over time though?

 

When I put a breather filter on my car this is exactly what happened to me. The codes were for random and cylinder specific misfires, the codes were thrown at idle. It's my bet that some how your hose going to the valve cover from the Frank is thier blocked, crimped or clogged in the Frank tube. At idle the ECU expects a "leak" after the MAF, this would be air going from the Frank/Stock unit into the valve cover. So it leans the mixture some, only all the air is going through the TB. Hence a lean condition causing a misfire.

 

Thank you I will have to check this today.