The problem started 4 months ago with it misfire code which progressively got worse and finally on a cold night it felt like I lost a cylinder . So I decided to start digging in and find problem. I switched out the spark plugs swapped coils and willl swap injectors.
Reasons for a p0303 spark plugs, coils ,fuel injectors, valve's either bent stuck loose or oil deposits on the intake side of the valve those would be the easiest of the problems to solve. Worst case would be a blown head gasket or some other intake manifold seal
The car is a 2009 HHR ss with 185000 kilometers and has been pretty much mechanically trouble-free since ownership other than a few sensors and rusted fuel line.
https://m.youtube.com/watch?v=nOjVH2tdgrI
Intake . Then injector rail
https://youtu.be/WBOA1yrd42k
https://youtu.be/yF0Kc0m_ldg
https://youtu.be/iEOYHUfUVJM

The next video to come will show how badly oiled the intakes are

 

Have you done a cylinder leak down test yet? https://www.chevyhhr.net/forums/how-...-engine-56053/

You may have bad gunk built up on the intake valves, if so, a good shell blasting would clean it up.

 

This might help.....

https://www.chevyhhr.net/forums/how-...lves-ss-56184/

 

Check your PM
There is a link to a pdf of all the specs you will need.

 

I was pretty far gone nothing that a deposit cleaning would solve. It was going to be my next step before the engine went really bad. Thanks for the link 2 all the info to get started

 

I took the valve cover off and there were no broken parts so the next thing I will try is taking off the intake to see how bad the deposits are and see if I can locate a valve that is not doing well. Secondly to do an ohm test on the fuel injectors I'm hoping it is a and injector and we can put this thing back together. The videos are not very good but I will get better at them. 9

 

And the investigation begins. Just a note, When you replace the injector seals you need the tool to install and resize them after you install on the injector. Also, the newer ones are compatible with E-85 whereas the factory ones were not.

It has been found that an injector seal leak will cause the same symptom.

 

If you need injectors....

https://www.chevyhhr.net/forums/clas...w-price-57307/

 

The next few videos will show the injectors and the intake valve covered with oil so I believe they the valves are not sealing properly as I added a quart of oil before it began the project and that oil ran down the valve and onto the injector. What part of the injector needs to be replaced the blue rubber ring or the metal bushing.

 

Really having a hard time visualizing this. You haven't linked any videos.

Not understanding how oil is traveling from the filler cap to the valve, and then to the injector. The business end of the injector is inside the combustion chamber, have you pulled the head off?