Need Help Diagnosing Sluggish RX Heritage 99 EJ251

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Need Help Diagnosing Sluggish RX Heritage 99 EJ251

Postby Tristan » Sun Apr 08, 2018 4:01 pm

Hey guys. So recently I bought a 99 Subaru Liberty RX 2.5 (first Subaru that I've owned, 3rd card).

Initially it was sluggish and hesitant when I put my foot down, and still had the crap battery dealer put in (it was for 2k so not expecting much) so put in a new one which had its own problems (had to put new battery terminals ends, the part that goes over the posts of the battery, and extend positive cable as it was too short).

Started to run like a champ and since I didn't know when last had an oil change, I did just that. Owners manual states to use either 5 w 30 or 10 w 40 (used 10 w 40), and still ran really nice but went back to sluggish and hesitant. Happened to have had half a tank or so left, decided to fill up. Since filling it isn't hesitant any more (its UL91 rather than UL95 cause most of the time I'm broke AF).
BTW car is an Auto (I can drive Manual, just needed a car that works and handles nicely to get work)

Edit: Got a sound recording of what the does and what I mean by hesitant/sluggish.

I'm thinking it's an fuel issue (injectors, Fuel pump, Fuel filter).

Any ideas as to what the issue may be, as I already have a laundry list of things to fix.
Thanks in advance.

List to fix;
Windscreen chips (Just need a new windscreen but that $400)
Fuel Filter
Fuel Pump
Possibly Automatic Transmission filter
Last edited by Tristan on Mon Oct 08, 2018 1:51 pm, edited 2 times in total.
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Re: Need Help Diagnosing Sluggish RX Heritage 99 EJ251

Postby ahrexwagon » Mon Apr 23, 2018 9:14 pm

Try the following;

-Knock sensor is the cheapest starting point at only like $20and super easy to swap out
-throttle body and/or throttle cable, can be gummed up/sticky which will affect idle and possibly rev response
-spark plugs/leads
-check over any vacuum hoses that may have come loose/cracked
-injectors may be blocked/clogged
-fuel filter
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Re: Need Help Diagnosing Sluggish RX Heritage 99 EJ251

Postby Rodger125 » Tue Apr 24, 2018 11:27 pm

Don't rule out the fuel pressure regulator....
Replaced mine... Made a massive difference....
But mine was the 2000 model 2.5i rx and unfortunately the only regulator available was a genuine one... Cheapest I could find was $238... But worth it.
My mechanic tested the problem by measuring the fuel pressure after running... Leave it overnight and read again..
If the pressure has dropped or takes time to build.. It is probably the regulator.... And you will not get full power as your injectors don't get full pressure...
(it can be a leaking injector overnight leaking into a cylinder... But I think you would get a puff of grey smoke in the morning)...
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Re: Need Help Diagnosing Sluggish RX Heritage 99 EJ251

Postby bigBADbenny » Wed Apr 25, 2018 8:10 am

Air fuel fire.
Air: pressure test the inlet tract post maf, use 1psi intitially and smoke or bubbles to spot leaks.
Clean the maf indirectly with crc maf cleaner aerosol, be gentle! Subaru upper engine cleaner/seafoam.
Clean throttle body/plate, and ICV.
Fuel: Subaru injector cleaner, new pump & fuel filter, possibly fpr too.
Fire: check leads, coil packs, pull spark plugs: read the business end to see if lean/rich/good, electrode condition and gap.
Replace if out of spec or worn and recheck after 200klm.

Maybe flush n refill the auto too...

That’s scraping the surface diagnostically, but those are the basics :)
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