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**NEED HELP**97 Legacy Violent Shaking Under Acceleration


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52 replies to this topic

#1 dzld231

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Posted 22 July 2011 - 09:44 PM

Well, I recently got a 1997 Subaru Legacy L sedan from my brother, it has a problem with the AWD. Here's a video that explains and demonstrates everything. Please, any help is much appreciated!



#2 Fairtax4me

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Posted 22 July 2011 - 10:30 PM

Auto or manual trans?

Kinda sounds like a misfire. Typical misfiring under load due to old plugs and wires.
Might be worth it to just replace those anyway if they haven't been changed recently. Get the other tune-up stuff too, air filter, fuel filter, PCV valve.

Probably have some loose heat shields too. That's the rattle sound.


Drivetrain related, heavy vibration such as that is consistent with a failed U joint, carrier bearing, or CV joint, or poor quality replacement half-axle. Drivetrain issues do not tend to be intermittent in nature (there one minute, gone the next). Axle or driveshaft problems will generally be present under load of some sort, (accel/deceleration), or at certain speeds when driving. This lends credence to an engine condition as the source of your problem.

#3 grossgary

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Posted 23 July 2011 - 06:37 AM

i can't watch the video due to connection speeds.

violent shaking under acceleration has always been cv axle related (particularly the inner joint) in my experience but there are other causes.

aftermarket cv axles are particularly prone to this and are one step above scrap yard junk. look at axles and see if they look old, torn boots, or recently replaced with an entire aftermarket axle.

and +1 on ignition - plugs and wires can make the car nearly undrivable, the engine in that car is not very forgiving with plugs and wires. it is best to stay with NGK plugs and Subaru wires. let us know what kind of plugs/wires are in it.

#4 heartless

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Posted 23 July 2011 - 06:59 AM

Clue number one - Check engine light is on - GET THE CODES READ!!!! :rolleyes:

Sorry, but the CEL will NOT come on for no reason - if it is on, there is a reason for it -
find out that reason and fix the problem - duh.

most of the large chain auto parts places can usually read the codes for you for free
(places like advance auto, autozone, etc)

Edited by heartless, 23 July 2011 - 07:03 AM.


#5 dzld231

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Posted 23 July 2011 - 04:55 PM

My brother told me that the CEL is on for 3 things,
1. Torque convertor lockout failure
2. Bad oil pressure sending unit *Fixed
3. (cant remember, fail.)

The front driver side has a new cv axle.

Tune up and coolant flush/exchange will be done soon.

*Ill get the codes read tonight so I know for sure.

#6 heartless

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Posted 23 July 2011 - 06:36 PM

*Ill get the codes read tonight so I know for sure.


Good idea.

#7 dzld231

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Posted 23 July 2011 - 08:24 PM

CEL CODES.

P 0136 - O2 censor circuit, bank 1, censor 2

P 0325 - Knock censor circuit (When I start my car I hear a knocking sound for literally about a second. Doesnt happen everytime I start it but about 80% of the time.)

P 0400 - EGR Flow (I have no EGR system, this I already knew)

P 0740 - Torque convertor clutch solenoid circuit open

Any ideas?

#8 Fairtax4me

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Posted 24 July 2011 - 01:04 AM

Read this thread concerning the P0325
http://www.ultimates...ad.php?t=120610

Oxygen sensor is a typical replacement item after 100k miles. Could be a dead sensor, or it could be related to the problem.

I'm not 100% sure on the EGR valve, which years had it and which didn't. There was a year that all engines got EGR valves. Before that automatics had it and manuals for the most part didn't. If yours doesn't have EGR, but you have a code for it, then you might have an engine swapped car. Very common for people to swap a dead 2.5 out for a 2.2, so it's not inconceivable. Pic of an EGR valve just incase you don;t know what to look for. http://memimage.card...00015_large.jpg Back side of the intake manifold on the drivers side. Easy to spot.

The P0740 code can have a few causes. Several sensors, wire harness problem, could even just be related to a running issue. It won't typically cause any problems though. Worry about the other stuff first. The knock sensor problem is a big one on these and could very well be the cause of your shaking/vibration.

#9 dzld231

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Posted 24 July 2011 - 01:09 AM

Thanks bud, I'll take a look when I'm on a computer, I'm just on my phone right now. And it's 2AM and I have to work at 10, so I'm gonna go to sleep. Thanks again. Anymore opinions and/or advice is greatly appreciated!

#10 heartless

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Posted 24 July 2011 - 07:12 AM

both O2 and knock sensor can cause serious running issues like you are experiencing.

fairtax has pointed you to an excellent article on the knock sensor.
too bad there isnt one as good about the O2 sensor... :rolleyes:

General rule of thumb is to start with the smallest number code and work your way up.
In this case, replace both O2 and knock sensors and see how it goes.

#11 johnceggleston

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Posted 24 July 2011 - 07:20 AM

P 0136 - O2 censor circuit, bank 1, censor 2

this is either a bad rear o2 sensor or a bad connection / wire. it is a circuit problem. check the wiring at the sensor, clean the cennoector. it that does not help buy a cheap replacement. (cheap is ok for the rear sensor, not the front sensor.)

P 0325 - Knock censor circuit

this is probably the sensor, replace it. $56 at autozone. the old one will have cracks in it, i bet. DO NOT over torque it during install.

P 0400 - EGR Flow (I have no EGR system, this I already knew)

i just fixed this code on my 95 lego, it has egr. my fuel filler neck had a rust hole in it. replaced it and now no p0400. is this even possible??

P 0740 - Torque convertor clutch solenoid circuit open

like the o2 sensor, this is a circuit problem. it could be a bad solenoid or wire or connector. or it could be a side effect of another problem.

Edited by johnceggleston, 24 July 2011 - 07:22 AM.


#12 dzld231

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Posted 24 July 2011 - 07:51 AM

Can anyone tell me where this o2 sensor might be at? And how much does it cost for one? Also how much will the knock sensor run me?

Another problem I'm having is an oil leak... Its happening up high somewhere because it's dripping down and burning on the exhaust. Is there any common spot I could check first where this happens often on this vehicle? I got my oil changed 2 days ago and was kinda embarassed when smoked billowed out of the hood into the guys face haha.

#13 dzld231

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Posted 24 July 2011 - 07:55 AM

Didn't notice there was a second page with another reply, thanks for that. I have no EGR valve/solenoid, the guy my brother bought it from removed it. I have no idea why. When my brother bought a new car two weeks ago he bought a 95 legacy lsi sedan and he showed me what the EGR was and went and looked at mine and there is nothing there.

#14 johnceggleston

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Posted 24 July 2011 - 11:04 AM

I have no EGR valve/solenoid, the guy my brother bought it from removed it.


well that explains the p0400 trouble code. ignore that for now. and move on to the others.

#15 heartless

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Posted 24 July 2011 - 02:21 PM

this is either a bad rear o2 sensor or a bad connection / wire. it is a circuit problem. check the wiring at the sensor, clean the cennoector. it that does not help buy a cheap replacement. (cheap is ok for the rear sensor, not the front sensor.)


oh yeah, i frequently forget that the later cars have more than one O2 sensor... :rolleyes: mine only has one, and if it goes south, causes all sorts of running problems.

#16 grossgary

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Posted 24 July 2011 - 02:21 PM

i'd clear them all and see which ones come back first. address in that order, except ignoring EGR codes, those don't cause issues. i and many others are driving around with EGR removed on ours and codes with no issues, so that's not the problem if it was done right.

knock sensor causes the most drivability issues in my experience out of the codes you're showing.

#17 dzld231

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Posted 24 July 2011 - 06:07 PM

Just out of curiosity, why do people remove the EGR system?

#18 Fairtax4me

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Posted 24 July 2011 - 11:04 PM

I can only assume it was removed because it was causing problems. Whether it failed or was just plugged up and causing a running issue is hard to say.
It isn't necessary per-se, but it does help prevent detonation (spark-knock), and helps control emissions by lowering the temperature of the combustion chamber under certain driving conditions.
Overall though, it's not worth putting back unless you REALLY want to get rid of the CEL.

#19 dzld231

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Posted 24 July 2011 - 11:16 PM

Could the knock sensor create an "artificial" knock? I made a video on my iphone of it this morning, but it wont upload to youtube now....

It makes a knocking sound for like a second. maybe like 4 quick knocks... Could it just be like that because there is no oil at the top of the motor when sitting?

#20 dzld231

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Posted 25 July 2011 - 12:39 AM

Not sure if this is goin to work but I'm gonna try and post the YouTube link to my video, I finally got it to upload.



#21 grossgary

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Posted 25 July 2011 - 02:14 AM

knocking on start up is probably not caused by the knock sensor. there is piston slap, which is very common in EJ engines and then other causes for that too. unlikely electrical in nature.

knock sensors off ebay are around $30-$35. chandler motor sports has a wide variety.

#22 Fairtax4me

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Posted 25 July 2011 - 12:28 PM

The word "knock" is used to describe many different conditions. The type of knock that the knock sensor detects is "Spark knock", also commonly known as "Pinging", or incorrectly, "valve rattle". This is a noise created by excessive combustion pressure.

Your knock at start-up is a different kind of knock entirely. That's a dry valve train. I would guess the oil weight is too heavy, so the rockers don't get the correct oil pressure right away.
An oil change with the proper 5w-30 grade oil, and a quality oil filter such as Purolator should cure that.

#23 dzld231

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Posted 25 July 2011 - 11:35 PM

Literally just changed the oil 3 days ago at a quick lube place. It has 5w30 in it. Guy at advanced auto said to use Lucas oil treatment and it will coat things better? What are the most common oil leaks on these cars? I have a leak that is burning off in the block or exhaust and it's pissing me off :(

Gonna order knock sensor and o2 sensor tomorrow I believe. Not buying from autozone or advanced cuz they want almost $100 for either sensor.

#24 WoodsWagon

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Posted 26 July 2011 - 07:20 AM

It's accelerating too quick to be missfiring, and the CEL is not flashing while he's accelarating, so I think the missfire diagnosis is a red herring.

There is a fair bit of driveline vibration and a ringing/jingle noise from the shifter area when coasting. I would look at the rear driveshaft U-joints carefully, especially the one right at the back of the transmission. If that joint breaks (and I've seen it happen), then the driveshaft whips around and punches the shifter up out of the center console. That also forcibly shifts the transmission into park at speed, rips the rear O2 sensor wiring off, and batters the exhaust. It's ugly.

Now, since it's an automatic you can run it without the rear driveshaft. If you find one of the u-joints or the carrier bearing is loose, pull the driveshaft out. It's 4 bolts where it attaches to the rear diff flange, and 2 bolts in the middle at the carrier bearing. A smooth cylindrical plastic cap from a spray paint can happens to fit well as a cap on the rear output of the transmission. Use a cap with no vent hole in it, put some RTV sealer around the outside of the cap, and gently tap it in. You don't want it bottomed out on the splined shaft sticking out of the transmission.

I'm telling you this because it looks like the car is a beater, and it's unlikely you'd spend the money to replace the driveshaft. Having a FWD car is better than a car that self-destructs, so the paint cap plug is the lesser of two evils.

Clear the codes and see what comes back. The O2 sensor, bank 1, sensor 2, is the sensor after the catalytic converters. It's function is to monitor the catalyst efficincy, and you can ignore it and it won't affect anthing else.

The EGR code, if the system has been disabled or removed, won't affect how it runs much. So don't worry about that.

The knock sensor code is a big issue. When it finds the knock sensor not working, it can pull timing and make it absolutely gutless. That one is worth fixing. The sensor is usually the culprit, and make sure the wire connection is pointing 45 degrees to the rear and middle of the engine, then tighten it. Don't crank on it, and make sure it's oriented the right way, and that should fix it. The plug for it is right under the throttle body.

The trans code is an issue too. Your gas mileage will drop a fair bit if it can't lock up the torque converter. Fixing the broken wire, or dropping the pan and replacing the solenoid would be worth doing. But, if it's an around town beater, don't bother.

Edited by WoodsWagon, 26 July 2011 - 07:28 AM.


#25 dzld231

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Posted 26 July 2011 - 12:49 PM

MY CAR IS NOT A PILE OF ************!

Just kidding, yes it is. But it is my only pile of ************, so I need to fix it. Haha. Thanks for the help bud, I think Im going to order a knock sensor right now.

Also, where and what is the torque convertor? Any diagrams/pics of it so I know what Im looking for? The only Subaru I have owned was a 1990 Loyale sedan that was FWD Auto. Ive never worked on or dealt with AWD before. (But its fun as hell in dirt parking lots, I know that for a fact!!!)

Thanks guys, I really appreciate the help!




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