P0301 - Cylinder 1 misfire 2011 HHR 2.2 Ecotech

Engine was replaced in August 2020 with 2.2 ecotech from an 09 Cobalt LS. So I don't know if I should get help here or go to the Cobalt section so I'll start here.

Car ran fine after the engine was replaced. I blew the first engine at 126,000 miles. It had the timing chain issue. Anyway it ran fine but I was getting a P0446 code and was having issues putting gas into it. That comes back to either the purge or vent valves. I have not replaced those yet.

Right before Thanksgiving 2020 it had a small leak somewhere in the exhaust because I could hear it. While driving it the pipe broke open right before the flange where it connects to the exhaust manifold. It didn't fall off, just opened the hole larger. I had to replace that entire pipe with the cat and resonator as all one piece. When that broke open it threw the P0301 code and a P1174 code and the P0446 code went away.

So far I have replaced the cat, the spark plugs, the mass air flow sensor, and the fuel injectors. I only have code P0301 now and you can feel the misfire while driving it. We checked the fuel pressure last night and it was around 60 psi while running but 0 psi with key on engine off.

I am at a loss as to what else to do. All suggestions are appreciated.

Thanks,
Jessica

Spark, fuel, timing, and compression are all necessary.

Did the spark plug from cylinder 1 show any unusual condition?

The coil for that plug can also be tested, but it's probably just as easy to move the coil from an adjacent cylinder and see if the problem moves.

The injector would be the next suspect, but without a bi-directional scan tool a power balance test can be a little cumbersome.

Then there is compression, which can be checked with a compression or cylinder leakage tester.

I didn't notice any difference between the plugs. I will look again though. We did move the coil from 1 to 2 then swapped 1 with 3. Neither swap changed the code. We replaced all four injectors because the shop said that was the issue but it didn't solve anything. We are going to get a compression gauge this weekend and see what we get.
I will post my results.
Thanks,
Jessica

I'm sorry that I haven't updated. I'm lost as to what to do.

So we have replaced the following with no changes:
Spark plugs
Fuel injectors
Fuel Injector Insulators
Fuel Injector Wire Harness
Mass Air Flow Sensor
Coil Packs
Catalytic Converter
O2 Sensors
Throttle Body
Fuses and Relays

The engine still shakes and gas mileage is horrible, about 13.5 MPG. When starting it after it's been sitting or when really cold it acts like it's not getting gas. I have to pump the pedal to get it to start.

We did the compression test on the cylinders and they were all between 155 and 160 psi on initial crank and maxed at 210 psi when key was held till they maxed. We weren't all too sure how to perform that test but performed the exact same steps on each cylinder so I think they are all good.

We did a smoke test and that showed us the leak at the fuel injector insulator so that's why we replaced those but it didn't make a difference.

Now one thing someone mentioned on another forum was the possibility that the computer could be the issue as my original engine was an LE8 and the "new" engine is an LAP. The LE8 is the flex-fuel version of the LAP. While I have NEVER run E85 could that still be an issue? Does anyone know how to determine if it is the computer?

Thanks,
Jessica