I have a 97 Subru legacy sedan and a couple of months ago the enjine light came on and I took it to 2 mechanics who said the throtle sensor and knok sensor were causing the problem. The 1st guy said don’t worry about it won’t hurt the engine of cours he didn’t tell me about the Knock sensor one. The 2nd guy said that it needed to be fixed becasue it was messing with my idoling which is true sometimes I notice it runs a little high cause the rpm goes up and down except when I am driving steady then its ok. My question is do I need to fix it and does it make me use more gas and what the heck is it? Should I take it to the dealer to have them fix it? Thanks, Cindy
Take it to a reliable independent mechanic and let him/her fix it.
The throttle position sensor tells the engine’s computer how hard you’re stepping on the throttle by measuring the position of the throttle plate. That’s one of the signals that the computer uses to determine how much gas the engine needs, and thus how long to keep the injectors open during each “pulse” (squirt) of fuel. If that’s sending an incorrect signal the symptoms can be exactly what you’re describing with your idle.
The knock sensor is a doohicky mounted on your engine’s head that senses the shock waves of preignition (which we hear as “pinging” or in extreme cases “knocking”). It backs the ignition timing off a bit to prevent the pinging. Knocking would be a much more severe condition and backing off the time would be unlikely to help. You should get this corrected also, as that shock wave stresses the parts from the piston on down and can even burn a hole in a piston.