I have a 95 Impreza with a 1.8L. For quite a while it's started hard when it's warmed up just short of operating temp. Cold starts are fine and, if it comes up to temp and I shut it off for a very short while no trouble. If it warms up part way or if it begins to cool down it 'sometimes' won't fire. Lately it's even not wanting to start on hot days (90+F). It turns over great but won't fire. I can ALWAYS pop start the car and it runs fine once started. Sometimes opening the air filter cover helps it fire up. Since this began I've replaced the air filter, plugs, wires, coolant temp sensor, MAF sensor, PCV valve, a fuel injector and fuel injection pressure regulator.

 

Where should I look next? I really need this car running. At 150K it should have lots of miles left but I'm running out of money and ideas.

Coolant temperature sensor, located on the coolant cross over pipe beneath the intake manifold.

 

May need replacing (they're cheap - use Subaru Genuine) or may just need cleaning.

 

Emily