I have two hhr, my 2011 2.4l. I am an Uber driver and have driven over 66k miles last year. I use it exclusively for Uber. That average speed is around 37 mph. I change the oil monthly. I had run e-85 file for a month, then decided the mileage was not worth the saving. I started to notice the engine running rough with the normal engine codes for missing on cylinder two. And turns off traction control. OK I have tried as much as possible.
Have reaserched here and everywhere. I have conflicting reads of testing. I have done compression test. 3 of the cylinders are the same 160, cylinder 2 is at 90. But it builds up fast like the other three. But stops at 90. So now I have done a leak down test. All four are exactly the same. Input at 100 and leak down about 90.
I think in tolerance. No sounds and no bubbles in the radiator.
I thought I had a blown head gasket. Not so sure. Can you loose compression from an injector? I have listened to them with a stethoscope and sounds the same on each. No water in oil and no oil in the radiator. I cannot drive this car until I repair it. Oh I'm at 240K on the odometer. And I noticed hearing loud valve chatter in the morning and goes away quickly. I don't hear that on my wife's 2006 HHR 2.4LT. Thanks for any help.

 

Could be timing chain!

 

You mean the chatter might be timing chain, right?

Those test results are indeed puzzling. I cannot think of any reason why you would have such low compression in #2 and not be verified by the leakdown test.

90 PSI is very low compression and, if correct, the reason for the misfire.

10% leakage is not good, but not completely unexpected with high miles like you have. Just to verify, you were using a full 100 PSI for your leakdown? Not with a cheap(like harbor freight) tester that only allows you to put about 12 PSI in?

EDIT: Here is a link for https://www.chevyhhr.net/forums/how-...-engine-56053/

My post #6 has a video and tips on how to make the Harbor Freight tool useable.

 

As for the injector, it's not a direct injection engine, so no!
I suggested the timing chain, but it could be a VVT solenoid, altering the valve closure.
It could also be a lot of things, if it were mine, I'd have torn it down by now!
But I can't do that over the internet, so we could keep guessing and pondering!
Please let us know what the out come is, to assist others should their issues be similar.

 

I never did get a clear answer(in my other thread) to my question of 'is VVT active during cranking'. DrLoch said that "The VVT sprockets are spring loaded to a straight up center position, the VVT solenoids direct oil pressure to the sprockets to vary the valve timing one way or another from the straight up mechanical setting. "

Since they need oil pressure, I would guess that VVT is not active during cranking. Someone please correct me if I'm wrong.

 

Fascinating system, I would conclude no oil pressure, no VVT.
Would the spring loading , advance or retard the cams?
I'm going to have to research that!
And so if no VVT during start up , why would only one cylinder have low compression?
I'm thinking an intake valve has an issue

 

But an issue with a valve would certainly show itself with the leakdown test. I'm still thinking cheap leakdown tester. With 10% leakage, there should certainly be audible evidence of the leakage. Unless it's only putting 12 PSI in, then it would be much harder to hear it leaking out, and it may not be enough pressure to cause it to leak much.

Just have to wait for Scorangehhr to answer that question.

 

There is a remote possibility that an injector seal or cup has failed.

They have a ceramic cup that has an O-ring seated in the head then the injector has an O-ring seated in the cup.

 

The injectors are in the head porting into the intake runner, prior to the intake valves.

 

I made a leakdown tester as per Eric the car guy on YouTube. I defiantly had 100psi. Input. I was holding off terring it down further as I have already started it. I am not sure what to do next. It did not start this issue until I had run E-85 gas for a month, which for me is about 9000 miles or more.