Q. I just bought a 1996 Hyundai Elantra with 40K miles on it (4 cylinder automatic, fuel injection, abs brakes, a/c and cruise control). When driving and maintaining a steady speed, the engine will sometimes speed up and slow down for no reason. Occasionally, when driven late at night, the engine will stop or backfire violently, and the car will resume driving as if nothing had
happened. There is no engine light, and it happens only when my foot is on the gas.
The TPS was just repaired, and the car drove beautifully until later that night. My friend has a driveway which is a quarter mile long, and is unpaved with rocks and potholes. After I had driven it on that the problem came back again. Thinking back, I realized that the night after I had driven on it for the first time the problem began. Could this be throwing my TPS off? Or is possible it wasn't the TPS in the first place?
Also, if this problem can occur this easily, would adjusting the TPS be a DIY job? And if so how would I go about it?
Thanks for taking time out of your day to answer my question.
Neil
A. That is a very weird problem. The Throttle Position Sensor (TPS) is not so sensitive that driving on a bumpy road will throw it off. In fact, there is nothing in a car that will be thrown off by a bumpy road.
I'm at somewhat of a loss to try and explain what is happening. I guess the best starting place is to check all the connectors and make sure they are clean and tight. A loose connection will cause problems when you hit a bump or pothole. It will happen so quick that the computer will not store a code.
One other thing that comes to mind is a Crank Angle Sensor (CAS) going bad. They can be affected by bumps and thumps. You can try tapping on it after the car has run a while and see if the symptoms manifest themselves.
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