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.

I would test your throttle position sensor. Since you use lower amounts of throttle most of the time, the electronic guts wear out faster on the low throttle input bands (where you are having a misfire). All they are is a potentiometer that changes resistance of signal voltage to tell the ECU what percent throttle demand there is.

 

The TPS governs alot of things like timing advance. If you punch the throttle, the timing advances and the injects extra fuel for more power/acceleration. However, the throttle plate also has to be open to let in air to allow that to happen. What I think is happening is your engine is hitting a short-to-100% throttle inside of your TPS so the engine thinks you are punching the gas, richening the mixture, not letting in enough air causing the smoke/misfire.

 

http://www.justanswer.com/subaru/39j64-want-know-check-tps-sensor-subaru-99.html

Got my car back today running significantly better (for now at least, problem is/was intermittent) mechanic checked fuel pressure all within spec, compression tested cylinders within spec albeit slightly different across the 4 bores (car is nearly 20 years old so not surprising). Checked and recalibrated TPS which he said was slightly off, replaced fuel filter and advised me to steer clear of Shell 98 and stick with BP Ultimate 98 (AU market names) fuel. He also regapped spark plugs to 1 mm or just under to try and reduce spark time thus increasing number or sparks per second to burn more fuel as it is a town driven car, not a racing machine.

 

Seems like much of the problem lies in basic tuning neglect over the years rather than specific failure of any one part considering new o2 sensor also improved problem but did not rid of it completely.

 

Whilst car is 100% better than it was it still doesn't run perfectly but mechanic reckons that is fuel quality related and possibly the slowing down in response time from the fuel injector relay under the dash which controls fuel injector solenoid operation and speed.

 

Proverbial food for thought.

some things that helped me if you havn't checked it yet is egr valve

 

[ame=http://www.youtube.com/watch?v=hkkhwBe8HDQ]How to change or clean your EGR valve-98 Subaru Legacy - YouTube[/ame]

 

a you tube video showing cleaning it. The EGR solinoid will be gummed up too. Also those thin vacuum lines could be clogged. I cleaned mine and have about 50% better off idle response. 100% would be to replace it. but 50% was free in the cleaning.

Today I swapped out the plug wires with OEM Denso units. Also changed out the PCV valve (because it was cheap). No difference at all. It still bogs down very badly when accelerating. It is Sunday tomorrow so I have a little time in the afternoon to try some things. I am going to try testing the fuel pressure while driving. I will update as I find things.

Got my car back today running significantly better (for now at least, problem is/was intermittent) mechanic checked fuel pressure all within spec, compression tested cylinders within spec albeit slightly different across the 4 bores (car is nearly 20 years old so not surprising). Checked and recalibrated TPS which he said was slightly off, replaced fuel filter and advised me to steer clear of Shell 98 and stick with BP Ultimate 98 (AU market names) fuel. He also regapped spark plugs to 1 mm or just under to try and reduce spark time thus increasing number or sparks per second to burn more fuel as it is a town driven car, not a racing machine.

 

Seems like much of the problem lies in basic tuning neglect over the years rather than specific failure of any one part considering new o2 sensor also improved problem but did not rid of it completely.

 

Whilst car is 100% better than it was it still doesn't run perfectly but mechanic reckons that is fuel quality related and possibly the slowing down in response time from the fuel injector relay under the dash which controls fuel injector solenoid operation and speed.

 

Proverbial food for thought.

 

Reset ECU and mechanics tune up has made car run perfectly. Make sure you gap the plugs and do the fuel filter.

Okay, an update here. I checked my fuel pressure while driving the car up and down the road. It maintained a steady 38-42 psi even while bogging down terribly. It also kept that same fuel pressure while accelerating at full throttle (which the car still does well). I am sure that finally rules out the possibility of fuel pressure problems.

 

My next try will to be replacing the front o2 sensor with a factory item (as suggested). If anybody has any ideas I am sure listening. This little thing is getting annoying and expensive.

Hello mrclownprince, I looked all over for my egr valve on my Subaru engine. Then it hit me. I have a 2.2 L engine. There is no egr valve on a 2.2. At least not that I can find. The video you show is for a 2.5 L engine. I can't use this info on my 99 legacy L but I am going to clean the EGR on my 2003 Legacy L which has a 2.5L.

Thanks.

have you done a compression test to see what that is?

 

checked your timing?

Update...I was looking at some of the other posts and there was one that dealt with this same problem. He talked about the green ecu test mode connectors under the dash and how they were connected. They are not supposed to be left connected (apparently).

 

I looked under my dash to check my ecu test connectors and found they were not connected. But I did find something a little frightening. One of the previous owners must have installed some kind of aftermarket electronics and used all manner of wiring splices to install it. I have wires spliced into other wires and wires just cut and hanging bare. I don't have time to work on this anymore tonight...this will be a weekend project. Wish me luck...

I checked my fuel pressure and found that I had 38-42 psi at idle and when I pinched down the return line the pressure spiked up to almost 70 psi. I took it out for a ride and ran the fuel pressure guage out from under the hood so I could view it while driving. The car acted up as always...but the fuel pressure remained at near 40 psi. I am sure I can rule out any kind of fuel pressure issues.

 

I also replaced the plugs and wires with Subaru items with no luck.

 

I talked to another shadetree mechanic about this problem. He suggested that I may have a problem with the torque converter locking up too soon. If the torque converter (tc) locks up at a low rpm it would cause the engine to bog down. It would also answer the question as to why the car accelerates hard when under full throttle (the tc would unlock).

 

Is there a way to run the trans with the lock up portion of the tc permanently unlocked?