Bought a 1998 Subaru Outback 2.5Lt engine 5 speed manual a few days ago. Runs great when cold surges and jerks in all gears at all speeds once it is warmed up? I have replaced plugs, wires, fuel filter and upstream 02 sensor to no avail. I would appreciate any feedback I can get. Thanks.

Is you CEL on?

I'd check for Codes.

 

It may be that your neutral switch is out and the computer does not know when your trans is not in gear.

+1 to check for codes, great suggestion.

 

MUST have 4 tires all the same brand/model/size. and 'near' each other in wear.

 

the 5spds can buck/jerk with torque bind after they warm-up. Does the car feel smooth if you coast in N after it's warmed-up ?

 

if the engine is acting-up after it warms up - could be the Engine Temp Sensor (not the temp gauge on the dash) It may be bad - telling the ECU to keep 'choking' the engine with fuel after it's warmed-up.

 

I wouldn't rule out a bad knock sensor - inexpensive ebay parts seem to work well for people if their KS is cracked/bad.

Worth inspecting insdie the plug tubes for oil too.

Edited April 11, 20169 yr by 1 Lucky Texan

If this is an engine issue (which it sounds like) and no check engine light I'd be looking at mass air flow sensor first.

 

knock sensor, coil and coolant temp sensor as secondary possibilities.