Thanks but that's the first thing I look for when I get a car! Great to have, and use it all the time. I have a Haynes copy sitting here on my computer desk. But I also agree with what you said about lasting a long time. Mine has almost 146k on it, and it's still running strong. Has one squeak/rattle from the rear end, but that's it...unlike the HHR It's in great condition, and it's never really had a problem (other than intake gasket, but that's common.) I'm not too concerned about this issue, it's just finding it I'm concerned about. It's a great car, and this is just an issue. All cars have issues, especially once they get older, and this is nothing big.

Thanks again guys for all of the input. My dad doesn't really know what might be causing it, but he hasn't had a chance to look at it really.

Dustin- Yes, it does have the 3.1 motor (great motor IMO). I will check for carbon build up, since the car never really goes on long trips or anything, it's more prone to the build up. (Trust me, this happens way too often in my truck)

As for the fuel filter, I just replaced that in the fall....so I'm sure it's not that. FYI, the filter on that luckily is on the bottom of the gas tank...much nicer than our HHRs! As for the pump, not sure... I can hear it working, so that's a good step!

No lights on, no codes...so that's no help for me. I guess the next thing I'll try is accelerating with the brake like you said to see if it's the plugs/wires...

 

Also, I saw something online about the Torque Converter Clutch (or the solenoid) going bad on these cars. Anyone heard of that? It does seem that this surging happens more at 45ish and above speeds, but it's really hard to tell. Can't really notice it in the city, but at idle it's slight, very slight...

 

Speed and load related..fuel filter...........easy money and probably needs one anyways...

 

I just don't understand though, if it's only 6 months old at the latest. I mean, I guess it doesn't hurt to try though...

 

Ooooo....thats kinda new for a filter,,but then bad gas can do strange things...I wasted a new filter by running cheap cleaner in the tank once....tough one...a lot of possibles there, but no codes..hmmm..would look at all fuel possibles as all the electronics are monitored,,they don't monitor liquid..also check your evap can or a lose vac line....

 

And that's why it makes me mad...

I have run different fuel system cleaners through the car before... Wonder if one of them could have hurt the brand new filter? Doubt it though.... Hopefully I can drive this tank of gas out, and I'll fill it up with some good fresh new gas. See how that does.

 

Throw some Hi-Test in it, & maybe a good Injection cleaner first..
Sounds like a possible gas related issue..

But hard to diagnose over the net..

 

I was going to ask but figured you had already ruled out bad gas........ Seems you haven't. Fill it with some good premium.

 

Yeah, I'm going to put some premium in from a good brand (probably Shell). Don't know if their gas is any better than Kroger, but who knows... I'm not driving very fuel efficiently either, so I can use it up a little faster... I'm going to hope that's what it is, since like I said the gas is 5-6 weeks old.

 

Is your problem a rythmic surging or a more rough run condition? If you have a rough run condition I'd suspect that fuel would be your concern rarely will poor fuel cause a rythmic surging similar to someone stepping on the gas in time with something. Like I said from your original post it sounds as though the computer is trying to compensate for unmetered air and is moving the IAC around. Unplug the IAC at a high point in the surge and see if it sticks to that idle. If so the computer is seeing a goofy reading from some sensor. If it was poor fuel or low fuel pressure you would see a rough run condition even with the IAC unplugged.