Hello everyone,
I have a 2010 Sebring with a fresh 10,000 mile 2.7. It's a fresh long block that a dealer installed after a rotating assembly issue killed the original engine. The car has a slight misfire at idle but doesn't have an issue when anything above idle. The check engine light is on and the code is the p30030 random misfire. It never shows the cylinder that is misfiring. I've swapped coils around and no change. If I clear the code and do not let the car idle, the check engine light never comes on. After a few minutes at idle, it's back. I appreciate any advice you all can give.

Thanks,
Smitty

 

need a good scanner that can get into the misfire data to actually see which ones are missing then you can narrow down the issue better

 

Thanks for the advice. I found the issue. It was a weak coil on cylinder 1. It was an intermittent issue. I bought a new coil for that cylinder and the miss seems to have gone away. I will keep you updated.

 

Welp no luck. Misfire is back. I bought a ht301 foxwell scanner and can see the misfire counter for all cylinders. All are good except 1 and 5. Rear bank on the ends. Cylinder 1 has a new coil and plug because I unplugged the old coil and there was no change so I replaced it and the plug to be safe. The old plug looked okay. A little tan but not black like unburnt fuel. Any suggestions?

 

Move coil 1 and 5 to a different location see if the miss follows

 

It doesnt follow the coil on either cylinder.

 

I noticed in the live data the timing was all over the place at idle but is solid on anything over idle rpm. Manifold vacuum was 6.5 at idle and steady

 

so injector issue or internal engine issue

 

I did run a jumper wire on the esd relay to provide constant power to the injectors. I read somewhere to attempt that. There was no change there either. The engine is so fresh and there isn't any metal in the oil. It runs so well above idle and never misses a beat on the highway. No lack of power or anything. Just a very strange issue. Would you recommend trying a new map sensor? If it was an internal engine issue would it go away at 1000 rpm?

 

a single cylinder misfire would not be cause by a sensor that tells the engine the manifold pressure that goes to all the cylinders. DO a compression test on the cylinder effected see if they are the same as the others around it.