I have a 2010 9c1 impala with a 3.9 engine. My son was driving the car several days ago and the car was running great. He was driving about 50 mph with the cruise control on when he lightly braked and slowed to around 20 mph. When he tried to accelerate the car started missing and is throwing a p0300 random misfire code. I replaced all the spark plugs, plug wires, changed the coil pack and tested the fuel injectors and still have the p0300 code and the engine is running really ruff. The car has a fairly loud ticking noise that I am not sure if it is coming from the engine or the exhaust by the firewall. I was thinking maybe a clogged catalytic converter but the car has pretty strong exhaust coming from the tail pipe. The engine is jumping around and missing badly. It is not hard to start though, after sitting overnight it will start right up the next day but runs very badly. We are not driving the car as it is extremely close to being undrivable. When the trouble started my son drove it about 1.5 miles to a friends house and I had it towed home from there. I can not understand what happened, the car has always ran great. Its like someone flipped a switch. The p0300 code is the only code the car has. If I erase the code it comes back almost immediately . Whatever happened gave no sign or warning before it happened. Any help would be appreciated.

 

You friendly with your neighbors, or have a locking gas cap?

 

`I was wondering the same thing. No locking gas cap. I sold the guy across the street a 2009 impala for $1500. that he knew needed work. The guy has a bunch of crack heads hanging around his house. My son drove the car 12 miles before the trouble started. Would it take that long for something to get from the tank to the engine?

 

What I think, based on your post, is something in the gas tank that's being (pushed from the pump) to blocking off the fuel to the rail

 

I am going in the morning to oreilly auto parts and get their fuel pressure test kit (loaner tool) and see if that could be the problem. Anyone know what the fuel pressure should be? I really don't think my neighbors would mess with my cars but there could be something obstructing the line or maybe the fuel pump or regulator could be bad. When I tested the injectors I was getting fuel to them ,but don't know if the pressure is right. Thanks

 

When you changed the coil pack, did you know which of the 3 coil packs was bad? Are the other 2 coil packs firing ok? When the pack was changed was there any change in how it was running? If there was no change, then one or both of the other coil packs may be suspect.

 

I also have a 2007 impala with a 3.9. I swapped coil packs with it because I knew the 07 coil pack was good. Did not cure the problem with the 2010. The 2007 runs great with coil pack from the 2010 though, so the coils are not my problem.

 

I had a problem with my 2001 Impala and 3.8L where it was only running on 4 cylinders. With the engine off, I carefully put in adapters so I could see if a pair of cylinders was firing from a certain coil one coil at a time. I found the center and upper coil was firing and the bottom one was not. I swapped the center coil with the bottom coil and the bottom coil still did not fire. A new ignition module that the three coils plug into restored normal operation. One thing to note is that with the old module, it would run fine on clod startup, but would loose fire from the bottom coil after about 10 minutes of driving.

 

Trying to post a video of engine running but when I try and upload it says invalid file.

 

I pulled the rear valve cover today and found small pieces of metal or aluminum on top of the head. The rocker arms had very little play so I do not think the problem is a collapsed lifter. Anyone know what these pieces of metal could be?