Question2002 hyundai elantra is occasionally stalling at red lights and sometimes the check engine light flashes on and it jerks while i am on the expressway. I have taken it to 3 mechanics and they can't find a problem. There are no codes coming up. It only has 66,000 miles on it. I just bought it in January and wanted a reliable car. Please help.
AnswerNormally, any time the check engine lamp comes on, there should be some diagnostic trouble codes stored. The only exception to this is that the lamp turns on so you'll know it's working when the ignition is on and the engine isn't running. So if you've checked for diagnostic trouble codes and there are none, I'd primarily suspect an electrical issue-- anything that will cause a momentary lack of power to the engine control module (ECM). Since you don't mention the oil, brake, or battery lamps, I'm presuming that in at least some of the cases, the root cause isn't mechanical.
First, check the battery to be sure it's securely held in place and that the positive terminal doesn't contact any part of the vehicle. If this occurs, it will short the electrical system to the point where there's no voltage, and more importantly, it can cause a fire.
Otherwise, if that's okay, I'd start with checking the ECM relay and the power and ground circuits for the ECM. To check the power and ground circuits, you'll need a schematic, which you can view at www.hmaservice.com after registering for a free account. Schematics are in the ETM (Electrical Troubleshooting Manual) section.
