[Thoey]

The facts:

Rebuilt the ej25d in my 96 outback, starts and runs fine, vacuum is steady at 16 inhg, new o2, new maf, new ckp, fpr is not leaking, runs smooth as silk all the way up to 2500 rpm then falls flat on its face with no power at all. No codes set

The parameters:

Above 2500rpm timing is at 40 degrees btdc and stays there, o2 is reading very rich at .9v, below 2500 it still seems rich but will switch like its suppose to.

Extra:

I reset the ecu after installing new maf and seemed to run better, then got worse, then went back to the same.

Ideas:

Car also has map sensor but seems to be working ok (no strange values that dont make sense)
Plugs and wires (reused the old ones that didnt look bad)
Injectors not atomizing fuel (stock injectors)
Timing (since vacuum is good and it runs smooth under 2500 i dont think this is likely)
Knock sensor (least likely since timing is at 40 btdc)

Any ideas? Anyone else have this problem?

 

[Thoey]

Also thinking it could be the ecu since resetting it seemed to have an effect

 

[1 Lucky Texan]

kinda points to a sensor issue if it runs better immediately after an ecu reset. The reset forces the car to run with parameters from a factory default, then , it begins using sensor data to alter the a:f and maybe other changes. ECUs are extremely robust so, unless the car has been thru a flood or reverse polarity jump start, I wouldn't suspect the ECU yet.

 

[Thoey]

Feel like its a sensor also but the only ones i havent replaced is the map and the cam sensors and i dont think the cam sensor would be causing this since timing seems good. Since it flips like a switch from fine to no power something is comanding the injectors open too long, that could be the map but ive never seen an n/a car that has both a maf and map so i have no idea what the map is for, also ive checked for plugged exhaust

 

[rasterman]

Exhaust restriction?

 

[1 Lucky Texan]

maybe check for timing off 1 or 2 teeth. they can run sometimes.

 

[Thoey]

Yea ill have to double check timing next i guess, after that ill have yo get a used map and see if that changes anything, and if im really backed into a corner ill have to get a piggy back and tune it myself haha ill post updates but keep posting your ideas

 

[Thoey]

Update:
New map sensor installed
No change

New plugs wires and coil
On test drive seems to have better power intermittently over 2500
Got back from test drive and #1 misfire code pending
Go for another test drive same thing intermittent power
Get back from second test drive and number 1 is now missing constantly at idle, dont feel it under load

Getting really frustrated, installing all new ignition components causes a misfire? Wtf

 

[dmac3]

What was the reason for the rebuild. Did it happen to throw a timing belt? Eat a valve? I only ask because my brother had a 69 VW with a horizontally opposed engine that broke a timing belt and ate a valve or two.

He went through the whole process of a rebuild, but had the identical problem as you are mentioning. Ran fine at lower RPM but no power above a certain RPM.

It turns out that one of the crank journals where the piston rod connects was slightly bent from true due to the force of the valve on the piston during the failure. Took a while to diagnose this problem.

If you didn't break a timing belt or drop a valve, then disregard this comment.