93 Legacy engine hesitation when hot

elandissubaruelandissubaru Member Posts: 2
edited September 2014 in Subaru
My 93 legacy sedan LSi started to randomly hesitate at cruising speeds (not during acceleration or idle) last week. The engine will just drop RPMs for less than a second, then come back again. The problem is definitely worse after the car warms all the way up.

So far I have:
put in new spark plugs and wires,
changed the fuel filter,
changed the air filter,
cleaned the Mass Flow Sensor,
and changed the PCV valve

I am still having the problem. Any ideas on what to look at next? O2 sensor?



  • ateixeiraateixeira Member Posts: 72,587
    Spark or fuel, so you seem to be doing the right things.

    How old is that ignition coil? I replaced mine and it fixed a hesitation issues on a 98 Forester.
  • dlanningdlanning Member Posts: 8
    i found on my 93 subaru wagon lsi the gas cap was not venting so i replaced it and it work fine
  • elandissubaruelandissubaru Member Posts: 2
    Thanks for the thoughts..

    I don't know how old the coil is, but I checked the resistance across it, and it still matches the specs..

    Interesting about the gas cap - I kind of like the cap that is on there.. I'll have to see what is involved in replacing it - I'm assuming there are just a few screws..

    After doing those changes, it has still been hesitating very randomly - sometimes not for days. I ran a 'fuel injector cleaner' in two tanks of gas recently, and I haven't had any hesitations in the past week. I know that stuff is supposed to be a joke, but is it possible the injectors are just fouled and the in-tank cleaners are working a little?

  • ateixeiraateixeira Member Posts: 72,587
    Usually you get a check-engine light if there is a leak in the evaporative emissions systems, though.
  • dlanningdlanning Member Posts: 8
    ok i have aquestion for you do you leave the car running for long time at idle ? and then latter when start it and you go to drive it then starts sputering and is slugish and you have to turn off the engine and let it rest for 1 to 2 miuntes and then restart it and all is great. i have had experinced this before thih my subaru as well it now has 300,000 miles on it. so just for curisty have you checked the voltage fro the alt? and checked the smog hose that on the driver side valve cover that leads up to the pcv valve ? some times they get cloged up and need to be poced out with a screwdriver and then washed out with break cleaner .
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