When you floor it the auto trans downshift must like every auto trans ever made, if you floor it it will wind up then launch when it downshifts, if you let off the gas before it launches it may just wind up and not downshift, which means no launch, or very little acceleration. My truck is the same way, when the lockdown is hooked up it will downshift when I floor it, my 1992 and 1998 blazers, 1998 malibu, 1979 silverado, my mom's 2014 malibu, sisters 2014 spark, sister in laws 2014 equinox, etc. All do the same. Same thing with grandpas dodge ram, caravan, and grandmas kia. The purpose of an auto trans is to automatically shift when needed. I'm not trying to be a jerk, and I'm sorry if my explaination looks that way, hopefully this cures your confusion.

 

That seems to explain the poor MPG. That's a lot of "flooring" & "launching", mine rarely needs it except getting on the Interstate, but then I'm getting old.

 

I do not launch it often, nor floor it, though it seems to need more throttle than it used to. Again, my driving habits have not changed, yet the gas mileage has. If my habits had changed I would already know why it gets bad gas mileage.

 

OK. I was just going by what you posted.

"If my habits had changed I would already know why it gets bad gas mileage."

Didn't you say that you rarely drive it anymore?

 

Yes, as of this last week, I do not drive it often. However this problem has been ongoing for months now.

 

Bad Mileage! I've been searching the forum for insight into my problem and maybe here is the place to start. Haven't seen a thread discussing my situation.

I have an '09 HHR ST with 103K. Had the 100K servicing done last May, and this car has all the paperwork going back to new. I've had it 9 months. I've made several trips from the Bay Area down to San Diego and also to Sacramento, always kept my oil changed, always watched the MPG. I'm the kind of driver who coasts up to lights and accelerates easy with an eye on the tach. Up until July, the care gave me 22+ in town and an easy 34 on the highway. Then the mileage started to tank, just a little at first but then worse and worse. Not sure of freeway mileage at the moment, but I'm down to 17.8 city.

The weird thing is, I can't hear or feel anything wrong with the car at all. RPMs are right where they should be, acceleration and idle are normal. No roughness or hesitation, anything that would suggest clogged injectors or a bad fuel pump. No check engine light. The car drives great, just as it always has, except for the mileage problem. Can anyone point me in the right direction?

PS My mechanic suggests that one of the front bearings is binding and needs replace. I can't feel or hear a thing that would indicate that. Is is likely? Ol' Sparky wants another $350 just to look at it, and that's not really in the budget right now.

 

"one of the front bearings is binding and needs replace" - I gather you refer to the front wheel bearings - I would think you would feel it while driving - but sounds unlikely that is the problem, but it's easy to check: feel the hub/center of the wheel (compare the left and right sides) after a good run on the highway - if it's hot, then you likely do have a problem.

Or, raise the tire off the ground and rotate it feeling for vibration or noise. $350 to just LOOK at the bearings is pretty outrageous if that is what was meant. I'd do it for $50!!

 

The other test for bad bearings is to grasp the tire top & bottom and push/pull. If you can feel ANY movement it was bad a long time ago.

Usually they make a lot of roaring noise.

 

I'm pretty sure it isn't a bearing! So no one has any idea why my mileage would tank without any other symptoms? I have checked for leaky fuel lines. One think I have noticed is that it's a little sluggish when I punch it a little - something I almost never do. Seems like it used to have a little more response, but it's not enough to alert me to trouble. I've had a couple people take a look at it, and so far everyone is stumped.

 

Heck. I'm still trying to figure out what a HHR ST is. (post 26)

As a wild guess. Maybe have the catalytic converter checked. Could be early signs of failure/clogging and not "breathing" well out the exhaust.