Hello hhr owners, I have been having problems with my hhr and need a path to start. My car has been shifting hard, my tc light comes on, and it idles bad with a bad smell, I took it it to have the codes read. They told me it was cylinder 3 miss fire, so I changed the spark plugs and replaced the ignition coil. Now I am still having the same problem, no change in problems, any suggestions? please help.

 

I moved this thread and renamed it.

First the hard shifting and TC light are probably caused by the P0303 code.

What sort of bad smell? Anti-freeze?

Does water pour out of your tailpipe? Are you losing coolant?

I am aiming at a blown head gasket with these questions. Coolant leaking into a cylinder will cause a misfire, and kill a catalytic converter.

Did you vote for my dad for mayor 20 years ago? Your screen name suggests a connection to the Marine Military Academy.

 

Posting up what year, engine size and mileage would also help.

A different guess. Is the smell like gas ? Could have a bad injector causing a rich cylinder condition on #3. What did the old plugs look like ? Especially the #3 one.
If it's a rich condition, and you continue to drive it, you will eventually damage the catalytic converter.

In short. Without a little more detailed info, we're just blindly guessing.

P.S. Welcome to the site.

 

That may also manifest as a "sulfur" odor.