Hi Everyone,

 

This is my first EVER post on a Forum.  I hope it is in the correct place.  I have a 1999 Subaru Legacy L 2.2 with Hesitation and Low Power issues until 3000rpm.  So let me give the story and ask for advice.  Unfortunately, it has been to multiple mechanics and I have worked a lot on this car.....Even been to a Subaru Dealer.....

 

New Parts:

 

Knock Sensor

Front O2 Sensor

Mass air flow Sensor - OEM from Salvage Yard

Fuel Filter

Fuel Injectors

Throttle Position Sensor

Timing Belt is new and Covers have been pulled by Subaru dealer to check

New ECU

Vacuum appears to be fine and that according to 2 different mechanics and one of my friends who came over to look

 

If I reset the ECU and then drive the car it runs perfectly for around 15 minutes.  Then begins losing power at low rpms,  Once the revs reach 3000 rpm or so it is like someone flipped a switch.  I welcome inputs as I have thrown parts and money at this car until I am losing hope.

 

 

I was prepared to ask about plugs and plug wires about halfway thru reading. But now, I think live data may be the best way to proceed - seems A:F ratios could still be off since it begins running poorly aAFTER running well following an ECU reset.

 

though exceedingly unlikely - I wouldn't rule out the knock sensor - maybe you got a bad one or it was installed with too much torque or the cable routed over a 'bump' in the casting.(I have read that is an issue on some models)

I will check the Knock Sensor but even the old "looks" ok.  No cracks that I can see.....

 

I agree with Air / Fuel ratios but no idea how to check and am real tired of simply throwing parts at the car.  I can say that I feel I have reached the point of no return,  tool late to scrap the car. 

 

BTW, the ECU does not throw ANY codes.....

there can be 'pending' codes.

 

if you have a smartphone, an inexpensive ELM327 BT adapter and a downloaded app can be used to get more data.

 

also, any association with temperature or moisture/rain?

 

any wrecks or work done just before the problem started?

check your spark plug wires. I had a car that was doing the same thing. when i went in to do the head gaskets the spark plug wires were shredded. also check the compression on the engine. and fuel pressure

Thanks All,

 

Inputs are welcome.  Cause I have run out of ideas

 

Spark Plug wires are brand new.  Forgot to mention that....

 

I have an XiTech XR-90 OBD II Scan Tool.  No codes are in there....

 

Does not seem to matter dry/wet cold/hot.....Reset ECU and it runs fine for 15 minutes.