We have had our 2007 HHR since 7/5/2009. It's a great car that we love and maintain. Lately it will start, then buck and cough, and usually stall. Then it will start and run fine. Occasionally it will start rough, cough and sputter and then smooth into an idle.Once it starts and idles it will run fine and start every time on that trip. Since the battery in it was original,yep, 13 years on the original battery!, I thought that would be a starting point. I bought a new battery and installed it. (who thought it would be a good idea to put it there?). It started right up and I thought that was the end of it. Then today it happened again. I got my OBD2 reader and there are no codes. Where should I look next?

 

Do the simple things first such as clean the maf sensor and check the air filter. If issue still persists, check for vac leaks and fuel pressure at idle

 

OK, will do. Thank you.

 

And clean the throttle body.

 

Thank you. I replaced the air filter, bought the CDC kit and cleaned the MAF sensor and the throttle body. The TB was really dirty.. I put everything back together, made sure it was all dry, started the car and the same rough start. Does the car need to reset itself? Or do I need to go to the next thing on the list? If so, what's next?

 

check your spark plugs on their condition and gap range. then if they are in spec and aren't the issue go check fuel pressure at idle and see whats it's registering. I don't know much of these motors yet but from past experiences from other vehicles, that aren't direct injection(DI), idle is normally 50-55psi at idle. does the car run rough only at idle or do you feel the car bucking when driving at any speed?

 

It just starts real rough, coughs and sputters. Sometimes stalls and I need to restart it. Other times it coughs then evens out to an idle. Once it is running, it runs fine. I've never had an issue once we go, then stop and restart. It's always the first start of the day. The car is garaged and it's been warm, so cold isn't an issue.

 

First off the iridium plugs are not to be gapped, just inspect them, or simply replace the spark plugs, especially if they are original and over 100,000 miles. The wicks break off easily so that’s why you do not gap them .
AC Delco 41-103 is the part number, don’t think you’re gonna save a buck and get any other plugs, these Ecotec engines where designed for these plugs.
if you check the fuel pressure, you disconnect the fuel line at the fuel rail, use a 3/8 fuel line tool , connect the fuel pressure gauge and turn on the ignition to run , because the fuel line is disconnected, you do not start the HHR , and fuel pressure should hold at 55 to 60 psi for a few minutes.
remember to remove the fuel pump fuse while the engine is idling , then wait till it runs out of fuel prior to disconnecting the fuel line.

have you heard any rattling in the passenger side of the engine at start up? Could be the timing chain is getting loose. But that should thro a code.

 

No I haven't heard any rattling. The car has 122,000 miles on it. We have taken really good care of it. I replaced the spark plugs at 65,000. I did use Bosch plugs. What bugs me is that once it starts and we are on our way, it runs fine. If we stop at a store, it starts right up and runs fine when we leave. Wouldn't bad plugs or poor fuel pressure also make it run bad all the time?

 

I misspoke. I replaced the spark plugs at 47,000 miles and then again at 105,000 miles. I did use the Bosch 4482 4 prong plugs.