I have a 2013 Hyundai Elantra with automatic transmission. Recently the car loses power when trying to accelerate (flooring it does nothing) and has stalled a few times. The tachometer gets stuck @ 0 while driving regardless of speed and acceleration. And nothing happens when I try to manually downshift.
But it doesn’t always happen. Sometimes it works just fine and the tachometer pops back to life. When I brought it to my mechanic he couldn’t observe the problem and no error codes came up.
Any insight as to what the problem might be or what I should tell the mechanic to look for would be greatly appreciated.
When the tach is working correctly, does the engine always run well? If so, might be some subtle problem with the sensor that sources the rpm signal for the tach, usually the crank position sensor. If powertrain computer doesn’t get a good signal from that sensor, it won’t be able to set the proper parameters for the engine to run correctly. Is check engine light on? Has anyone checked for stored diagnostic codes?
For the ignition switch idea above, as a test remove all the other keys from key-ring, and just drive with the single key in the ignition. Sometimes dangling keys cause a worn ignition switch to misbehave.
Yes, the engine runs normally when the tachometer works.
I keep all others keys on a separate key ring, so extra keys are probably not it. But I do notice that it seems to occur when I first start the engine. Tachometer gets stuck a zero and engine sputters.
That’s an important clue. Make sure to mention it to your shop. I’m guessing crank or cam position sensor, wiring & connectors between those sensors and computer, or faulty computer.
Could also be caused by failing battery or battery discharging overnight b/c of some unknown drain current path. After you start engine, battery voltage increases to alternator voltage. Ask your shop to measure the battery voltage before the first start of the day, then immediately after starting engine. Should be about 12.6 volts, then 13.5-15.5 volts.