Mysterious performance issue. Legacy 2.0r 165bhp 05 plate
 

Hi I've just registered here for some tech advice on my Legacy 2.0r 165bhp.

I've owned it 3 years or so and its covered 98k miles. It's a 2005 plate.

A fault with the car has developed where it's 'hunting'. This is manifesting as general lack of power across the rev range in all gears and the engine is noticeably holding back when I put my foot down.

I have had the following work done so far :-

replacement maf sensor

check of ground wiring which is good

vacuum checks which showed as fine

No fault codes showed up when a diagnostic was done ( although this wasn't at a Subaru dealer ).

It is about to get a fuel injection system check looking for a non electrical issue and also HT lead function check.

Has anyone had any experience with an issue like this and if so how it was resolved?

Many thanks in advance for any help http://www.uklegacy.com/forums/uploa...ault_smile.png

Change the fuel pump filter..........

https://cimg1.ibsrv.net/gimg/www.sco...9305840685.png

thanks I'll do that next. 👍

mysterious performance issue
 

Hi, I have got a 55 plate Impreza wagon with EJ20 engine, no turbo. I assume your Legacy has got no turbo? I think I may have a solution - this works for me.
The issue I have from time to time is very specifically a massive hesitation at about 2500 rpm in all gears. I have had the car for 9 years and have done 100,000 miles in it and it has done this from time to time until I found the following solution somewhere: Apparently it is linked to the knock sensor. If you accidentally put crap petrol in this becomes upset and to prevent 'pinking' it severely retards the ignition timing just when you could do with it not doing so. The ECU needs re training with the following procedure:1) Turn off the lights, aircon, stereo or any system in the car that draws extra current on top of the engine.
2) Disconnect the battery for 30 mins.
3) Reconnect the battery.
4) Before you start the car for the first time, turn the key to the ON position but do NOT turn the engine over. Wait 10-15 seconds so the electronic throttle body or IACV has time to go to the factory programmed home position.
5) After waiting, start the car and let it idle without any load, lights, A/C etc.
6) Every 20 seconds or so the idle will be adjusted up and down as the ECU tries to adjust it towards a stoichiometric fuel / air mix.
7) Leave the engine running for a full 10 mins but DO NOT TOUCH THE ACCELERATOR during this time or turn on anything that will cause extra electrical current draw.
8) Turn off the engine, and leave the key in the OFF position for at least 20 sec.
9) As per step (4) turn the key back to the ON position for 10-15 sec without actually starting the engine.
10) Start the engine and leave to idle for a further 5 minutes without touching the accelerator and without turning on other systems in the car.
11) Turn off the engine again and wait at least 20 sec before restarting.
12) Take the car for a test drive as the ECU should now be fully retrained.

Honestly I have done this several times over the years and it always works. Follow it meticulously. I try to avoid supermarket petrol now, and never go to my local Morrisons for petrol as this seemed to upset the car every time. If you leave it the car will eventually come right again once you have had a few fills of 'good' petrol. For some reason this is apparently only common to EJ20 engines with no turbo.
Good luck!

thanks man I will definitely try that!
..oh and yes it is indeed a non turbo engine.

You can't reset the ECU on Newage cars by pulling the battery. Only works on Classics.

Symptoms sound more like Maf than IACV but worth cleaning both.

maf has been replaced ( with expensive part not cheap one ) and throttle body etc. cleaned.. see my op. above.
Thanks for the reply though anyway :)

unfortunately I don't have a solution for you, but I have the same problem, if I reset the ECU memory, either by disconnecting the battery, or more usually using freessm, it runs great for a while, but gradually gets worse, until I reset again.

You've mentioned HT leads but also check spark plugs, air filter and PCV valve.

How did you get on with @Don Clark solution?

Would a faulty crank and cam sensor cause your issues too?

I've spent all day trying to get fuel pump parts as per Don's suggestion but cant find any without going to Subaru and waiting over 4 weeks for a Japanese import.. which is very frustrating.
To be honest the retaining clips on the fuel pump housing are broken so I need to buy some parts at the very least ( I've started a separate thread on this in fact ).
The fuel pump could easily cost over £600 just for that part alone dammit! :))

I've had a diagnostic done so I would've thought faulty sensors would show?