Sharpie’s UEC fuel rail soak to fix rough idle, hesitation..

Posts specific to the 2.0 litre Turbo engine

Sharpie’s UEC fuel rail soak to fix rough idle, hesitation..

Postby bigBADbenny » Fri Jan 17, 2020 9:57 am

This was a tip shared by former Subaru technician Steve Siladi aka Sharpie on the lib club Facebook group, in response to a gen4 GT rough idle diagnosis post. Thanks Steve, for sharing your knowledge.
Steve says this is more relevant for pre 05 cars due to a revision.

Fuel rails and injectors UEC (Subaru OEM Upper Engine Cleaner) soak:

This is an alternative to getting new stock injectors or getting your injectors replaced.
Note, if you do choose to get your injectors cleaned or replaced, be sure to replace all of the inlet manifold gaskets, below and above the TGV’s/injector housings. (Prefl: don’t have TGVs...)

Pull fuel pump fuse.
Cycle starter to reduce fuel pressure in rails, short cranks as to not burn out starter motor.
Remove fuel rail hoses supply and return where convenient and according to FSM procedures.
Use compressed air to blow remaining fuel from fuel rails.
Fill fuel rails/lines with UEC.
Let it soak, eg overnight.
Use compressed air to blow remaining UEC from rails/lines.
Reattach hoses as per FSM procedure, replace fuel pump fuse.
Key on to acc, prime fuel rails, check for fuel leaks.
Crank engine and pray :P

Alternatively, whilst soaking the fuel rails in UEC, remove the spark plugs, pressurise the UEC in the fuel rails (get creative here, eg use compressed air, pressure bleeder etc) and crank the engine using short cycles again.
Use compressed air to blow any remnant UEC from the cylinders, replace the spark plugs and resume the rails/lines soak.

The general idea is to use UEC in the rails, lines and injectors, instead of getting your injectors cleaned or replaced.

In general, proper diagnosis includes but it not limited to basics like compression test, inlet and exhaust vacuum tests, and in the case of a modern car logging the performance of the various sensors used by the ecu.
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