I recently purchased an HHR and I like everything about the car but it has a small hic-up. Once the car has warmed up and you are going down the road at a steady pace (30 to 40) mph it likes to jump from 1,500 rpm to 2000 rpm. Sometimes more than other times. It is very annoying because you feel like you are slighly taking off and then backing out without moving the gas pedal. I figured maybe it was bad gas so I ran several tanks of fuel through it and a couple times added fuel injection cleaners. I have cleaned the mass air flow sensor, gave it a tune up, changed the map sensor and may I say no check engine light all this time. I even serviced the transmission at the Chevy dealership. Two days ago the car decided to stop acting up which I was releaved. Then that second day I got out of work and when I started the car the check engine light came on. I drove to my friends house and on the way it was acting up again. He hooked up a code reader which come to find out it was the gas cap was loose. He cleared the code and no more check engine light. However it is still acting up with that flexuating throtle. I'm trying to give the car a chance and the Chevy dealer was no help and my mechanic can't figure it out either. Everything is fixable right? Not this car. Can anyone help with this one before I trade it off for a foreign vehicle. Thanks for reading my post.

 

Welcome to the site, you mentioned cleaning the MAF sensor, but don’t mention cleaning the throttle body. If you haven’t cleaned it , use throttle body spray cleaner and don’t move the throttle butterfly plate. Simply remove the four bolts and gently left it up a bit and turn it till you can spray the engine side.
In light of your statement the codes where cleared , disconnect the Negative cable at the battery while you clean the throttle, then after your done cleaning and reinstalling the throttle reconnect the negative cable , this will reset the computers and should resolve your surging

 

I will buy some throtle cleaner tomorrow. My mechanic said he sprayed it but he didn't mention anything about taking it out and spraying the back side. Thanks for the tip. I will keep you updated.

 

This is the speed where the transmission can't decide which gear to be in, isn't it oldblue?

 

Why threaten us? We don't care what car you have.

You recently purchased the car, your mechanic doesn't know how to fix it so you are ready to call it quits? Did you actually take the car to any mechanic? Or just talk to them?

My first thought is 30-40 MPH is right about where the transmission is trying to decide between third gear and over drive. Could be normal. I don't know because you are expecting the car to idle while driving.

Does it do the same thing when you drive in "I" instead of "D"?

 

Yes that surge when doing 40 mph is a similar problem. It could also be a vacuum leak , but that would thro a code.

 

From what I googled to learn more about the 4T45E trans, it has a PWM (pulse width modulation ) TCC (torque converter control) valve/solenoid.
Lock up is gradual thru the speed range and not just say 50 mph.
There is no off/on lock up like older units.
Could there be a problem with it not controlling pressure to the torque converter clutch ? As in it being worn/bad ?
There have been people having to replace the shift solenoids that seem to be more common., so why not the TCC soleniod ?

 

Yep, that's what we are trying to narrow down. Another "should throw a code".

 

Yes Don I agree.
No codes makes it rough to diagnose.

 

My 07 had that 40 mph problem, it didn’t throw a code. I had the TCM reflashed , problem solved. Now the program is for 2008 and up, and I see OP has a 2010
These 4T45E automatic transmissions are very sensitive to fluid level, both low or high can cause problems.
But let’s see if the throttle body is the culprit first.