I've been getting a CEL and ran the codes. 14 came back relating to random misfires on all four cylinders. Sort of odd since I'm not seeing any noticeable performance problems. It's a 2008 MCS with 35k miles.

Anyway, I changed all four spark plugs and did a Seafoam treatment...still getting the CEL. Went to Autozone and cleared the code. CEL came up the next time I started up the car. 100 miles later the CEL is still and the car accelerates just like it should.

Any idea what's going on? It's driving me nuts...

 

Are these the codes?

P0300 - Cylinder Misfire, Several Cylinders
P0300 - Combustion miss, multiple cylinders: Fuel injection deactivation
P0300 - Combustion miss, multiple cylinders: Increased exhaust emissions
P0300 - Combustion miss, multiple cylinders: Increased exhaust emissions after start sequence
P0301 - Cylinder 1 Misfire Detected
P0301 - Combustion miss, cylinder 1: Fuel injection deactivation
P0301 - Combustion miss, cylinder 1: Increased exhaust emissions
P0301 - Combustion miss, cylinder 1: Increased exhaust emissions after start sequence
P0302 - Cylinder 2 Misfire Detected
P0302 - Combustion miss, cylinder 2: Fuel injection deactivation
P0302 - Combustion miss, cylinder 2: Increased exhaust emissions
P0302 - Combustion miss, cylinder 2: Increased exhaust emissions after start sequence
P0303 - Cylinder 3 Misfire Detected
P0303 - Combustion miss, cylinder 3: Fuel injection deactivation
P0303 - Combustion miss, cylinder 3: Increased exhaust emissions
P0303 - Combustion miss, cylinder 3: Increased exhaust emissions after start sequence
P0304 - Cylinder 4 Misfire Detected
P0304 - Combustion miss, cylinder 4: Fuel injection deactivation
P0304 - Combustion miss, cylinder 4: Increased exhaust emissions

 

yup! exactly!

 

time to inspect those intake runners for carbon build up. heres something you can try, when you start your car for the first time of the day (vehicle has been sitting cold for @ least 2-3 hours) as soon as it starts let the idle set and then go WOT and look into your rear view mirror (or find a friend to watch your exhaust). if you see a ton of soot and black/grey smoke coming from your exhaust system on the first 3-5 hard WOT accelerations (Snap WOT) then you have a large amount of carbon deposit on the backside of your intake valves that is causing your combustion misfires.

 

Carbon buildup.

 

Did anyone here say..........CARBON?

 

Also, check compression/leakdown. Could be an issue with exhaust valves not seating.

 

probably carbon. has happened to me many times in three years. i'm still a bit mad about it. i've saved all of my gasoline receipts this time, so when it happens again in a couple months, i can cut off their "only use brand name premium" speech. that's all i've ever used, and now i can prove it. they make a killing off carbon cleanings, i'm sure, so there's not much motivation to fix the design flaw.

 

Ive been having the same problem, all the same codes come up... It only started AFTER i got the carbon cleaning. Those same codes popped last Wednesday morning as well as this Wednesday morning.

COuld it be that my timing chain has skipped a tooth? When I got the Carbon cleaning done, I had taken my car in to check the chain and tensioner. One of the plastic guide rails on was replaced, and the tensioner was to still fine. Could it be possible my mechanic WOULDN'T check the time chain length when he checked the tensioner?

 

Also spark plugs were replaced 2 weeks ago

 

This Would Be My Fix. 1) Seafoam 2)Another Seafoam Product In Aerosol Form, Forgot The Name. 3) Italian Tuneup

The Italian TunE Up Means Drive Your CAr For Fifteen Minutes Highway In 2Nd Or 3Rd Gear AT rev Limiter.

Done This For Myself And Usually Gets Rid Of Most Carbon Throughout EnGinr. Did I Plenty Of Times On Kther Peoples Cars Mini Or Not