'99 Legacy Wagon 2.2 Auto HORRIBLE ACCELERATION

[SubaruMyke]

Hi everyone,

I recently bought a '99 Legacy and it has a really bad acceleration problem.

Symptoms are:

*Barely any acceleration from a stop, I will have to push the gas pedal down really far and when I do that the car just jerks forward as if its choking. There is a major delay in acceleration and when the engine finally responds i get very little power.
*The car accelerates completely fine in highway driving and seems to be only an in town driving problem (at lower speeds).
*The problem is intermittent but frequent.
*Seems to get SLIGHTLY better when the car has been driven for 5-10 minutes, but still a noticeable problem.
*NO check engine light.
*No unusual sounds coming from the engine or trans.
*Car idles fine and engine runs smooth.

I just replaced the PCV as part of general maintenance and seafoamed through the PCV and gas tank. New air filter as well.


If you go to this link: http://www.consumerguide.com/subaru/leg ... 1995-1999/ (http://www.consumerguide.com/subaru/legacy/used/1995-1999/) and scroll down you'll see that a common problem is:

Poor transmission shift: Hesitation or poor acceleration may be due to the powertrain-control module (PCM) misinterpreting normal
engine vibrations as knock, and retarding the ignition timing requiring a replacement PCM. (1999)

Has anyone had this problem and if so, did replacing this fix it?

I am not that mechanically inclined and would like to have a good idea of what it is before I take it to Subaru and have them replace unnecessary things.

Any help is GREATLY appreciated!! Thanks

[Grimmrican]

When's the last time u changed the plugs,wires, and ignition coil?? That almost sounds like a misfire that u have. Or a MAF SENSOR problem or idle air control or fuel filter.... I'd start with a tune up

[1996Battlewagon]

Did it happen after you replaced the PCV and seafoamed it? Or did you do those things to fix the problem?

[Wiscon_Mark]

No CEL doesn't mean no codes (CEL bulb could be out too). Have you tried to have codes pulled?

[SubaruMyke]

Ok so my CEL must've been burnt out bc I took the car to advance auto and it was showing that the knock sensor needed to be replaced. So when I removed it sure enough there was a crack in the plastic which was causing the hesitation in the acceleration. I replaced the sensor and sure enough it's been great since then! Thanks for the help!

[SubaruMyke]

Scratch that the horrible problem has come back. It's hesitating and bucking just like before the sensor was replaced. The weird thing is that my old sensor was cracked so it really did need replaced. I've gotten code P0325 before replacing and after replacing. Last night I disconnected the battery for 1/2 hour and it still has the hesitation. I put the knock sensor on the same position as the old on and it's on their tight but not overly tight. I don't have a torque wrench, btw. I've already disconnected the new sensor and reconnected it to see if anything changes, but no luck. Just to be clear there is no audible knocking. Please help!! It seems everyone has had their problem fixed after replacing the knock sensor?

Also this problem is intermittent and sometimes goes away when the car is hot but not always. The problem has gone on before my seafoaming, oil change etc. but I do know the timing belt was recently replaced if that has anything to do with it? Also the car idles smoothly all the time.

[Huffer]

Did you pull any more codes? Get that CEL bulb fixed too, that's the first thing I'd do.

Then, I'd check your Throttle Position Sensor or your Cam Sensor. It sounds like mechanically the car is fine, but when you give it throttle from the pedal it's bogging.
Can you rev it freely using the throttle cable holder on top of the engine? If that works fine then the problem is on the cable slack between the pedal and the throttle holder.

[Neatfellen]

Have you checked the spark plugs and plug wires yet? I had a problem similar to that on a previous car and it was caused by a bad plug wire, replaced it and it was fine. but would check the plugs to as that should help as well.

[dplacencia]

I have seen bad front o2 sensors do crazy things and with out a check engine light. Clean the throttle body too...

[Neatfellen]

I have seen bad front o2 sensors do crazy things and with out a check engine light. Clean the throttle body too...
That's true as well, have known a lot of problems to come from O2 sensors.

[CarDoc]

All good points. Tune, TPS and front O2 sensor are common culprits. Either creating a malfunction will cause a rich condition, stumbling, loss of power and with a bad TPS, poor shift points in automatics. You may also want to check the Knock sensor again and make sure it wasn't overtightened, cracking it.

[ScaryFatKidGT]

Fuel and air filter while your at it

Couple threads away from yours viewtopic.php?f=11&t=27152 (https://sl-i.net/FORUM/viewtopic.php?f=11&t=27152)

[tnrknght]

To be honest, this sounds a lot like what was going on with my legacy wagon. If you really get on the gas from a stop itll bog down, but if you ease onto it, itll move steadily. I even used to feather it for a second before trying to move (now two cars later its almost muscle memory)

How many miles are on your motor? Turns out with mine it was the keyway on the crank for the crank pulley had notched out far enough to throw off the timing a bit. She ran rough and didn't like to jump from a standstill but if I treated her right she loved to go fast and started everyday. Currently undergoing a heart transplant to get back on the road with that one, driving my impreza in the meantime.

[Muse]

I had a similar problem, one of my plug wires had burned through. not all the way to the metal core, even, but enough to ground out on the block.
Hesitated real bad at anything but light accelerator use / 3000rpm. Go past an inch or so of pedal travel, and it would feel like the car was going to fall apart, Bluesmobile-style. Car was capable of highway speeds, and maintained them with ease, but to do 0-60 without bucking took a loooong time.