Monday Mar 12 2012
Car’s stalling could be due to a few different items
By: Tom and Ray Magliozzi
Click and Clack column
Dear Tom and Ray, My daughter lives in Anchorage, Alaska. She is a Wisconsin transplant who still believes her father (me) can help with anything. I need your help to maintain this myth. Here is the issue with her 2001 Subaru Forester: The engine starts right up in the cold (she parks it outside all winter). But when she goes back inside and leaves it running to warm it up, it turns itself off. Upon her return to the car, within a maximum of 10 minutes, she finds that the engine has turned itself off but the lights and radio are still on. She has a brand-new battery. Can you help me maintain my mythic status? — John TOM: Only if it wasn’t you who advised her to move to Alaska in the first place, John. If you sent her out there, she may never listen to you again. RAY: The car is starting fine so there’s nothing wrong with its cold-start operation. The problem occurs when the car is transitioning from cold-start to normal run conditions. TOM: That suggests that a sensor is bad and is telling the computer — erroneously — that the car is warmed up before it really is. RAY: So here’s your first mythic act, John: Ask her, “How long has the Check Engine light been on, sweetheart?” TOM: When she says, “Oh my God, Daddy, you’re psychic!” then you can say, “And how long has that no-good boyfriend been living in that apartment I’m paying for?” RAY: If the Check Engine light is on, her next move would be to take it to a shop and have it scanned. A mechanic will hook a computer up to the car’s diagnostic test port and read the stored error code. TOM: If I had to take a wild guess — which is all I do — I’d guess it’s going to be a bad coolant temperature sensor. RAY: The coolant temp sensor, as its name implies, tells the computer whether the engine is warm or cold by measuring the temperature of the engine’s coolant. If the coolant temp sensor is faulty and tells the computer that the car is all warmed up when it’s really not, the computer might then reduce the amount of fuel going into the cylinders, which could cause a cold engine to stall. TOM: Other possibilities include a bad oxygen sensor, which on an older car can cause the same problem as a bad coolant temp sensor. Or a vacuum leak, which is letting in too much air. That is the equivalent of “not enough fuel.” RAY: It should be something like that, John. Suggest those as places to start and you might come off looking like a genius. And if none of that works, you might be able to buy a few more months of this myth charade by angrily blaming it on us. We wish you luck, buddy.