I have a 2000 Subaru Impreza it has 130,000 miles on it. Problems started a few months back and I have tried several things to fix it to no avail. It hesatates when starting off then gets a surge of power once over 2500 rpm in every gear. It has a very bad jerking and bucking. The first thing I tried was to replace the fuel filter, then plugs. I then got codes and it said the accerator positon sensor was bad, along with downstream O2 sensor. I have replaced both of these still not better. I had the codes read again and now it says the idle sensor is bad? My question is would this cause the problems I'm having?

 

Yes. The TPS sensor is probably not bad. It probably just needs to be adjusted. Often people will try to adjust the idle speed by turning the throttle stop screw on the throttle body, and that just causes problems because the ECU sets the idle speed.

 

Possible the IAC is bad, the style used on that engine isn't the most reliable, but check the TPS adjustment first.

 

Downstream O2 sensor could be bad depending on the code.

Can you post the actual P0xxx numbers?

how long since the timing belt was changed? could it have slipped a tooth?

Edited August 17, 201411 yr by 1 Lucky Texan