Hey all, I'm original owner on a 2011 HHR 2.2L (non turbo) automatic. I've had 120K trouble free, hard driving miles. Lately I get a rough idle on a hot start, and it lasts 30 sec or so and clears up. No codes and no other symptoms. I popped a scanner on and saw #4 was showing up to 40 misfires so I swapped in a new coil there, but still have the problem. I can't find anything on a search. I was going to check fuel pressure, see if maybe #4 injector is leaking down, but its just a wild guess. What do you think?

 

You may need new spark plugs. The Ecotecs like the AC Delcos.
Spark plugs:
2.2L/2.4L - AC Delco part number 41-103 (iridium)

to the forums!!

 

Hey, thanks. I've got about 15K on the plugs, haven't pulled to check them.

 

You could try swapping the plug from the misfiring cylinder with one from another cylinder, see if the misfire moves.

 

Sounds good man. I'm gonna pop out the plugs to read them. I'm wondering if I've got a leaky valve guide, dripping a little oil into the cylinder on a hot soak. I tried to get away with the quick fix. I know alot of guys have complained about the valves, and I really put this little motor through its paces, so just a guess.

 

Misfires cause CEL (code), since they will kill a cat real fast. Those misfires are probably phantoms. Maybe your scanner thinks you have 6 or 8 cylinders.

Do you check your coolant level regularly?

Fuel pressure would be a good place to look.

 

Welcome to the site, have you cleaned your MAF sensor and the throttle body? Also check the wiring connections and ground wires!

 

It's been a while but I fixed my problem, and I found it kind of by accident. First off, the scanned misfires were phantoms, I realized a significant amount of misfires should trip the check engine light. Scanning another car with no symptoms showed a similar reading. So last week, my belt started making noise, and a few days ago it shredded. While changing the belt and tensioner, I noticed some dark oil on the frame rail, it was directly under the tensioner access hole, under the engine mount. The oil looks like WD-40 or PB Blaster. I dried it up and it came right back when I started it up. (I had no idea the HHR used a hydraulic mount, but there it was.) So a new mount took care of the leak which may have helped the belt to fail, and now the car is smooth as can be. So if you come across a rough idle, check for an oil leak at your engine mount. I flipped the old mount upside down for the picture.

 

Thanks for the follow up, it will help others in time of need.

 

Great news, and information for future reference!