I picked up a 2001 Subaru legacy sedan, automatic today.  It has hard start, warm or cold, harder at cold, significant engine hesitation, backfires, and huge loss of power.  Barely made it the 30 miles back to my favorite shop.  No check engine at start, but code for front o2 sensor once I arrives and not long after I was on the road.  Car recently has had a new exhaust from engine to the back muffler.  All new o2 and converters.  

At idle seems to run decent, when I work the throttle at the engine, it rev's, but misses if I give it too much gas.  My gut is telling me fuel is the problem, but looking for ideas I might have missed.

 

I was thinking fouled plugs maybe, bad fuel filter, bad fuel pump, bad o2 sensor out of box or ????????

 

Anybody else experience this?

 

 

 

seems like previous owner was chasing a problem too.

does use of starting fluid make starting better or worse - that could point one direction or another. Is there oil on the sprk plug boots? have you confirmed cam/crank timing?

I’d be checking the cam belt alignment. Sounds like the cams could be out a few teeth... 

Cheers 

Bennie

thanks, those are excellent things to check today.  I will let you know.

Update.....  Looks to be the fuel pump.   Have one in a car we are about to junk and will swap that and see.

 

check for the cap o-ring problem on the pump.

was the fuel pump for sure.  Runs like a champ now.

 

Thanks for all of the good ideas!