99 Legacy Won't Accelerate

Hello Everyone,
My first time here. Let me see if I can do this right.

I have a 99 Legacy L with a fairly serious problem with acceleration. Maybe somebody has had the same problem and can help. It has the 2.2 engine with auto trans. 147K miles and is in overall great condition. The problem is that when I take off from a stop the car will bog down so badly it becomes actually dangerous to drive. It will accelerate like crazy if I floor the accelerator but anything part-throttle causes this problem.

I have no check-engine-lights lit up. I have also scanned the computer for codes and have found nothing. I have tried to be intelligent about changing parts to cure the problem... changing only the parts that made the most sense. Here is what I have replaced. The Throttle Position Sensor (and properly calibrated it afterwards), plugs (double platinum Denso), knock sensor (torqued to 15 ft-lbs), the coil, plug wires, air filter, both oxygen sensors.

I have cleaned the Mass Airflow sensor with the proper spray cleaner from NAPA with no luck. I should add that I had no improvement at all when changing any of these listed parts. The problem remained identical.

The only error code I have had was about 4 months ago and it referred to the EVAP system. I cleared the code and it stayed away. I have inspected and cleaned the electrical connectors for the engine and have checked the fuel pressure (34-36 at idle and 38-40 when revving the engine. When I plug the fuel pressure return line my pressure spikes up to 68-70 psi). I have run two cans of Seafoam through the gas tank with no change.

The engine will rev with no problems at idle and will also rev like crazy if I am driving and floor the accelerator. It is just this part-throttle driveability thing that has me stumped. It also idles in park with no problems. It also makes no difference if the engine is hot or cold. On rare occasion it will actually drive normally...but this is rare.

Any ideas?

Thanks,
Bob

Sounds like you have a failing front o2 sensor, bad ignition wire, failing coilpack or a cam or crank sensor that is going. The latter two would more likely than not throw a CEL and cause issues unloaded. The front o2 sensor, did you replace it with a subaru one? Or aftermarket?

aging knock sensor.?

He said he replaced it, and torqued it correctly.

Both of the O2 sensors were replaced with aftermarket items. Do you know of a way to check the operation of the o2 sensor without actual replacement? What would happen if I simply unplugged it for testing purposes?

I have swapped the coil pack and plug wires from a good working Subaru with no change at all. Both subarus worked the same after swapping over the parts.

1055 and Johnegg...thanks for the superfast response.

Bob

Ok. Is the front o2 a cut and splice? Or a pre wired? Im thinking your issue lies with that. In 99 they used an 'afr sensor' as opposed to a standard o2. Make sure you have the rifht ine in

Hello 1055,
I checked my front O2 sensor today and it appears to be the correct one. It has not been spliced in. I am going to try swapping in another front O2 sensor from a good working Subaru to test it. I will post again when I have more info. It might be a couple days.
Bob

They are very finicky in that year range. On my 99 ej22 i went four different aftermarket sensors before i went oem by vin to get the right sensor. Cost me more frustration than money.. true PITA.

Heres another question.. are your valve cover seals leaking around the spark plug tubes?

Hello again 1055, I just changed the plugs and there was no oil leaking down around the plugs at all. My camshaft seals and oil separator are leaking some but that is all. My plan was to pull the engine next spring and install a new Fel-Pro seal kit in it.

1055, when your front O2 sensor was causing problems what were the symptoms? Were they anything like mine?

Bob

Stuttering under half load, popping out the exhaust, terrible gas mileage and no code at first.

I have been away for a few days to get caught up on other projects but finally got back to the Subaru today. I tried cleaning the ground wires (4 of them) that are bolted into the top of the strut towers. There are two per strut tower. While I did this I disconnected the negative on the battery. I left the battery disconnected for about an hour. When I took it out for a ride it drove perfectly. I was very happy until I took it out for a ride again two hours later and it was right back to doing its super-slow acceleration thing again. I did notice that it blew heavier smoke out the exhaust when it was accelerating slowly. I am suspecting that it is shutting down a couple cylinders when acting up. I am ordering some new plug wires tonight and try that. I had tried plug wires before off of a Subaru that was working great. Maybe I just need a new set. We'll see.

Fuel issues maybe? My car is doing a similar thing but it wouldn't show up revving without a load if its the start of a fuel pump going or otherwise. I'll let you know how I go my car is booked in to the workshop today to get looked at, I don't have the time, energy or enough diagnostic tools to chase this horrendous ghostly problemo.

pqkillerAU,
Thanks for your input. I have a fuel pressure tester and I might have to hook it back up and (somehow) position the pressure guage so I can watch it while I am driving the car. I might have to remove the hood to make that happen. That will have to wait until the weekend. My new plug wires will be here Thursday. I will try those first just to rule them out.
I am very interested in finding out what fixes your Subaru. Thanks again.

Easiest way is to run it up on the cowl and under a wiper blade, thats how i do it at least.