We have a 2008 HHR with a 2.4l engine and an automatic transmission. We bought the car a couple of years ago and we never had any big issues. However, a couple of weeks ago, the automatic transmission suddenly started to act "weird". It wouldn't shift immediately and the engine would rev up. When we release the accelerator pedal, the transmission shifts immediately. The strange thing is, it only happens when the engine is cold! As soon as we have driven a couple of miles, the shifting works perfectly.
No error codes have been stored.
Did anybody ever experience a similar thing? Does anyone have an idea what the cause of the problem could be?
We really appreciate your help. Thank you in advance!

 

Check you coolant level, sometimes air in the cooling system can cause problems.
Check the TCM wiring connector for loose pins .

 

Thank you for your answer. We checked the TCM wiring connector for loose pins, everything is okay and very clean. The coolant level is a bit low. It's below the cold fill line, but the coolant is still visible in the coolant reservoir. But how could that interfere with the automatic transmission?
Thank you in advance!

 

Open up the fill cap on the filler neck on the upper radiator hose, if there is air in there, burp the coolant.

air pockets can cause the computers to get wrong temperature information. This tells them to adjust for that temperature reading and as such can change how the engine runs.

 

Oldblue is right.
Temperature is very important for automatic transmission operation. Therefore, the computer responsible for the operation of the automatic transmission takes these readings as paramount and adjusts the hydraulics according to these indicators. If the computer takes incorrect data as a basis, the automatic transmission works strangely. The cooling of the transmission fluid and engine oil takes place in the engine radiator, if there is little coolant, then the temperature data is incorrect or you have excessive heating.

 

Transmission fluid is cooled in the radiator, engine oil isn’t, except the 2.0 LNF and the early 2006 2.4 litre with the water cooled oil cooler



That’s the oil cooler , it’s water cooled

 

yes right
i wanted to write engine cooling

 

I know, lost in translation.