That’s correct, the 2009 Cobalt engine was a 2.2 with VVT but not flex fuel capability. All parts physically fit but the computer will not be happy with a 2.2 in place of the 2.4.

 

2009 HHR 2.2L Flex fuel : engine failed
Donor Engine 2009 cobalt 2.2L non-flex fuel

Local salvage yard said it was a compatible fit. I did the swap myself in my drive way. I kept the cobalt engine complete as i received it. Upon 1st start I got the vvt solenoid codes so I swapped them over from the old HHR engine and all was good for a few weeks. Then I started getting an occasional p0172 and or p0171... I then chased that by searching for vacuum leaks evap issues, fuel pressure issues... to no avail, Never changed any parts for I never found an issue. I then found my Fuel Alcohol % to be 80% so I was convinced that was my problem. I purchased a vxdiag tool to use the tech2win diagnostics to reset the Fuel Composition back to 0%. I still was getting the occasional 171. I am now convinced that all of that was just the symptoms to the real problem of having the incorrect Injectors for the HHR Flex fuel ECM... Luckily I still have the old fuel rail and injectors and will be purchasing a new o-ring and seal kit to go with the swap... i will let you know what happens.

 

Have a look to double check the exhaust manifold for cracks


You will have to remove the heat shield

Thank you for clarifying 2.2 to 2.2 both 2009, they will be compatible except the flex fuel

 

That looks familiar... for when I swapped the engine my HHR had that same exact crack... the new to me cobalt manifold did not... so I swapped it then. :)
More history I did this swap in april of 2022 last year. I have since put 15,000 miles on it just the way it is. I know I should fix the issues sooner but hey I am a busy person... but now my tags are coming up for renewal in April of 2023 so this is my motivation for getting rid of the engine light. lol
I am still at work... but the more I think about it and how easy is should be to swap the injectors I may just do it tonight...

 

Remember to release pressure from the fuel line.

 

I pointed out the wrong injector problem back in #18 almost a year ago (and repeated in #27.) You need to use not just the HHR injectors correct for your year but anything else that might be required for the FlexFuel designation, but I don't know what that is. Anything the fuel touches needs to be corrosion resistant including immune to galvanic corrosion, because E85 is not just much more corrosive than E10, it's much more conductive. The FlexFuels got a highly modified fuel pump module and a bunch of other measures to protect the systems from attack by ethanol.

I woldn't be surprised if the O2 sensors are different too.

Also, again, it's completely plausible that the phasers are different, because E85 can utilize much more aggressive cam advance, but if they are wrong, the ecm would be complaining pretty quickly with P0016/17 I would think. Maybe it's easy for someone to check those part numbers.

 

The flex fuel injectors should be all that’s required, the VVT phasers are same part number, fuel pump is way back in the fuel tank , so that’s fine, the O2 sensors are in the exhaust pipe and shouldn’t have been changed.
knock sensor camshaft position sensors and crankshaft position sensors are same also, it was easy to check!

 

Yep I read through everything and was very excited when I saw the confirmation from you all in this thread for I have been trying do diagnose this issue for while now. I just completed the swap of reinstalling my old HHR injectors along with new orings and seats. Lubed them up with some vasaline and reinstalled. I cleared the p0171 and fuel trims and fired it up and let it run for about 30 minutes in the driveway. I commute 45 miles one way so in the morning I will report once I get to work if any engine light comes on. While in the driveway I had up the Tech2win Misfire graph and it was clean! Which tells me this was the fix. For before the Misfire Graph would be littered with hits approximately 15-20 per 5-10 minutes scattered across each cylinder with most on cylinder 4 for what ever reason, which I noted incase I have and additional problem with cylinder 4...
I also hoped on Rockauto and checked all part numbers of the MAF/MAS/VVT/CAM/Crank sensors and more... all looked the same except for the injectors and rail. (HHR rail is rectangle and the Cobalt is round), I swapped the rail back too. So now the HHR has the HHR injectors and rail.
I also dug up the Junk yard receipt and found out that I lied earlier about the cobalt engine... It is actually a 2010 and I will list the VIN of the cobalt and my HHR in case anyone wishes to compare something.
HHR host chassis 2009 2.2L vin: 3GNCA33BX9S543930
Cobalt donor engine 2010 2.2L vin: 1G1AH1F54A7121279
Thank everyone!

 

The Cobalt in 2010 was not Flex Fuel either, I found several articles about converting to E85 and the main thing was to change the injectors, so I believe you’re gonna be just fine

 

Success!
I think my HHR ECM is much happier now! Everything makes sense now. After engine swap in April of last year the ECM actually did a very good job trying to compensate for cobalt injectors... It was throwing the trims as high as it could and thought it had 80%-90% alcohol in the tank because of the high trim percentages... I was not getting a engine light all the time and when I did it was p0172(Rich Condition). It was only like every 2-3 fill-ups I would get a light and then it would go out for a fill up or 2 and then come back. Drive ability was pretty good to be honest. I had to really pay attention to feel the slight missfire that could be easily mistaken for bounces in the road. Where it showed more was when at low speeds in a parking lot I have a 5-speed manual and it would lug quicker than it should as if it had less torque than is should. Then the cold hit St. Louis area over Christmas break and that is what pushed me to fix this problem. During the cold the starts in the morning were very hard... as if it was flooding itself and then once it started it would dial the trims back and drove fine. But still very annoying. I then purchased a vxdiag to use the Tech2Win program to do a Fuel Composition Reset for I was certain at the time this was my problem for I was getting a Rich Condition and the Alcohol was 80-90% meaning the ECM was dumping too much fuel through the injectors. So after the Fuel Composition Reset I immediately started to get p0171 (Lean Condition). Which now makes sense for the Trims take a while to compensate over time. And if I were to continue driving it I am sure eventually the trims would have caught up and I would have started getting the p0172 for the Rich condition again. But thankfully with your alls help I was able to locate the real problem of the injector difference from the cobalt and the HHR. This was a journey with a nice happy ending and I hope this info will help someone else too.
I would be happy to field any questions if you all have any.