QuestionQUESTION: My son has a 2009 Chevy Cobalt LS Sedan XFE, 4 cylinder, 2.2 L DOHC VVT, 5 speed manual transmission. Just last week at 56,000 miles, it had its mass air flow sensor and four spark plugs replaced to get rid of a bucking/surging movement when driving forward; also the "check engine" light was erratically coming on and off. It was believed it wasn't getting enough oxygen to the fuel. Okay, that problem is solved, but now it doesn't want to go into reverse backing up a hill. It will back up with no problem on flat ground. When forced to back up the hill (by my courageous husband), we smelled something burning under the hood when he arrived at the top of the hill. It almost seemed like it wasn't going into reverse gear, or something was blocking it. Is this just a characteristic or weakness of four cylinder,underpowered engines?
Thanks!
ANSWER: HI MARY ANN,NO THIS SHOULD NOT BE HAPPENING. THIS SOUNDS LIKE WHEN THE CAR IS IN REVERSE GOING UP HILL IT MAYBE PULLING ON A WIRING HARNESS BECAUSE OF THE TORQUE OF THE ENGINE IS SO GREAT. IT MAYBE PULLING TIGHT ON A HARNESS OF SOME SORT CAUSING THIS. IT WILL ONLY HAPPEN IN REVERSE WITH A GREAT LOAD ON IT WHICH IS TUGGING ON A HARNESS IN A DIFFERENT DIRECTION ,THAT IS WHY IT WILL NOT HAPPEN ANY OTHER TIME.. TELL ME WHEN THIS HAPPENS DOES THE CK ENG LIGHT COME ON OR FLASH ??? IF SO GET THIS CODE FOR ME BY MEANS OF A SCAN TOOL. THE SMELL COULD BE FROM THE CLUTCH BURNING OR SLIPPING BECAUSE OF THE WAY THE ENGINE IS RUNNING. NOT ON ALL FOUR CYLINDERS MAYBE !! THIS IS A GOOD QUESTION..KEEP ME UPDATED WOULD LIKE TO GET TO THE BOTTOM OF THIS,GOOD LUCK ,TOM
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QUESTION: Hi, Tom:
Thanks for your speedy reply.
Fortunately, my usual mechanic was in the area today and he came by to look at the car. No "check engine" light came on. He says the Cobalt is set at the factory for an idle at about 900 rpms. This cannot be changed. When backing the car up an incline, it needs about 1200-1300 rpms or the engine will run rough and that lowers the rpms available to it even more. So basically, you simply have to rev the engine more when doing this. The mechanic got in the car and backed it up successfully at the higher rpm range. When he used less rpms, it shuttered and acted like it was going to pop out of gear. Learn something every day! Never would have guessed there's more leverage against a car backing up than going forward in first gear up a hill! Thanks for your time, Mary Ann
AnswerHI MARY ANN, VERY POSSIBLE REVERSE GEAR IN THIS CAR IS HIGER RATIO THEN FIRST GEAR,SO IT MAY TAKE A LITTLE MORE RPM'S TO GET IT ROLLING..THAT WOULD EXPLAIN THE BURNING SMELL THAT YOU SAID THERE WAS. CLUTCH WAS OVER HEATED..OK HAVE A GOOD REST OF YOUR WEEK END..TOM
SORRY,,I WANTED TO SAY HIGHER GEAR RATIO NOT LOWER..THANKS FOR THE GOOD RATTING...TOM
