Partial throttle cut out

[destey]

1997 Subaru legacy GT with 2.5. Motor has 210,000 miles and was rebuilt a few years ago for the headgasket. I bought the car last december with the issue present and got a deal because it ran the way it does. So I've never had the car when it was running good.

 

This is continued from a thread a few months ago. This problem rarely triggers a CEL. The cutout happens maybe 30-40 times on my 45minute drive to work, and the CEL comes on once a week (and never during the cutout, always when the car is running fine, a minute or two later). The missfire has read "missfire" and "cat efficiency below threshold" both don't tell me very much because they're just symptoms not the cause

 

The cutout only happens at low throttle, like 0-30%. If I push the accelerator down, the engine pops back to life. The car idles fine, but shifting is hard because when I go to release the clutch and push the gas, it does the cutout almost every time.

 

The car has plenty of power and runs fine when the issue is not happening.

 

The cutout feels like the key is turned off, a complete loss of power. When it comes back on, there's a thud (from the drivetrain I think).

 

I've done the following

 

upstream and downstream o2 sensors

MAF sensor

TPS sensor

IAC valve

fuel filter

spark plugs

spark plug wires

coil

igniter

 

I've also put new terminals (cut the wire, sanded off corrosion, soldered on new terminals) at all the ground locations I could find - left and right strut towers, by the battery, near the IAC valve on the manifold. I cleaned off the positive and negative terminals on the battery and the cables.

 

Nothing has made any difference in the slightest. I'm still on my theory that there's a bad ground somewhere. Does anyone know any other locations for grounds?

[Suba9792]

did you use OEM plug wires? this random EJ25d miss fire seems to be common. Vacuum leak?

[destey]

everything oem.

[destey]

Bump. Anyone have any ideas? Some days are better than other, today was really bad. It would cut out at anything less than 1/3rd throttle. It acts just like the key is turned off, as I turned the key off while driving down the road and its the same symptom.

 

It also was idling at 2500rpms when I put it in neutral. Funny thing is when I come to a stop, the idle comes down to normal.

[destey]

Anyone think this could be my EGR valve? I've noticed the valve never moves when I rev the engine by rotating the throttle body. I can slide the egr valve up and down without sticking but it doesn't seem to move by itself I see there's a solenoid of some sort connected that looks pretty rusted, could this be bad? Is there a way I can check this system or disable it?

 

thanks!

[destey]

Still having the problem. Finally got codes read (drove a long ways to an autozone).

 

Cylinder missfires in 1, 2, 3, 4

o2 sensor upstream

o2 sensor downstream

EGR

 

Is what the guy wrote down. I'm thinking the downstream and missfires are caused by the upstream and the EGR.

 

But I've put in 2 new OEM o2 sensors. So it must be the wiring to the computer, right? Or the computer itself? Does anyone know what wires going into the computer are the O2 sensors? I was going to run my own wiring and bypass all the OEM subuaru wiring.

 

I'll pick up a EGR solenoid at a junkyard and throw it in there. Or would pulling the electrical connector factor that out of the equation?

 

thanks in advance!!