I had my car parked since Saturday evening and figured i'd take it to work today. It's been a bit on the damp side here in NH. I started the car, it seemed to sputter a bit and have an abnormal idle. I ran both GoPoint software and Dash Command to read 3 misfire codes. This is the second time it's happened to me in the last several months. I blamed the first on from cheap fuel. The car didn't seem to run any different than normal. I cleared the codes, restarted the car, ran both apps and found no codes. This is a 2010 MCS with almost 30K. Thoughts? Just a fluke?

 

I take it the idles was erratic, could be the HPFP. Sounds like a fuel or coil problem.

 

The idle wasn't bad really. It almost huffed and puffed at first start which triggered me to scan. It ran fine too. I pulled the coils and blasted them with a shot of air in case there was any moisture in and around the plugs.

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Well this is for sure, something is going to fail eventually. It could be anything, how long does this huff and puff last? I had a lean condition a year ago with 100% power loss at 65 MPH and never received any codes. Sorry I can't be of more help to you, it's tough to diagnose a problem when they don't happen often. I'm sure it's probably something small like a sensor.

 

The noticeable difference in idle only lasted for a minute or so. The exact same thing happened twice now.

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A minute is a long time, the ECU should have given a code after that amount of time. Whatever is happening seems to be getting progressively worse as time goes on, I'd call that a good thing because then you can diagnose it easier.

 

Sounds like HPFP to me.