1996 Subaru Legacy Brighton SW jerking at 80 MPH

[DiamondDW5]

My 1996 Subaru Legacy Brighton Station wagon will not pass 80 MPH without jerking and check engine light blinking. This started about 2 weeks ago after I got a tune-up and front and back brake system, does anyone have an idea of what the problem might be.

[lord flashheart]

First off Why do are you driving so fast? 75mph is the highest speed limit I know of and 55-65mph most places.. second, you should pull codes, cuz when the CEL comes on, that's usually the car trying to tell what's wrong. and What do u mean 'jerking'? Do you mean the steering wheel shakes/viberate?

[Navi271]

yeah, "jerking" makes me think of the steering wheel moving around. Are you talking about the engine bogging down or something?

And I think if the CEL is blinking, there's a catalytic converter destroying misfire. And what flashheart said, codes please!!

[DiamondDW5]

Ok, so I don't have code digits with me right now, but I do know I have a Cylinder 4 misfire which I thought was fixed but it's not.

It's the car jerking, including steering wheel. I can be going 60 MPH and it jerks, sometimes it starts at 80MPH, which I rarely ever do 80MPH, but I had showed someone what I was talking about and instead of jerking at 60MPH, it did it at 80MPH.

Anyway, my first Check Engine Light experience started September 2010 with Camshalf sensor code and the Cylinder 4 Misfire. I got a full tune-up, oil change and Cam sensor all done November 2010. My check engine light was off for about a month straight. January 2011, I got a front and back brake system, along with my state / emissions test, which I passed everything. Two days after my inspection, I was driving to work doing about 65MPH and experienced jerking. I pulled over and my car was still jerking like something is loose under my hood. I called the car place I go to and they told me to turn the car off and turn it back on to reset the "computer" or something. I shut off my car and turned it back on and my Check Engine light was on, SOLID.

I went to the car place later on and he said one of the wires from the tune-up he did came loose. But now that I am still experiencing the same thing, he says it's the Misfire. Anyway, does anyone know what a Cylinder 4 misfire is / or means?

Oh, and when the Check Engine light comes on, it goes off after a few start-ups. I can leave work with it on but if I stop at two grocery stores, it will turn off. Then, turn back on when I'm on the highway heading to work in the morning.

[lord flashheart]

So we will start off with what a misfire is (keep in mind this is simplified). Essentially its when that cylinder is suppose to fire but it doesn't. Now there are 3 main things you need to make a cylinder fire properly. You need compression, ignition, fuel. So when the intake valve opens the piston moves down(sucking in air) the fuel injector shoots a little bit of fuel into the intake, that gives you fuel and air. when valves close, and the the piston moves to the top of the cylinder chamber, that creates your compression, then your ignition coil sends the spark to the spark plugs and ignites the compressed fuel. The burning fuel pushes the cylinder down that's where you power comes from. So if your missing any of those things the cylinder won't generate power that's a misfire. Because it misses firing that cylinder. Anyways. The steering wheel shaking kinda sounds like a separate issue from the misfire. I would probably say its warped brake disks or a bent CV (continuous velocity) axle possibly a bent wheel. that is usually the tipical suspects of wheel jerking/vibration. It's worth it to buy premium breaks because the cheepo brand tend to warp rather quickly. As far as the misfire goes it sounds like imo spark plugs. Because after you drive it, it warms up and doesn't misfire. It's really tough to say with out seeing it. I would say take it to a different mechanic (possibly the dealer if you can afford it) and have them look it over and check the work that the other mechanic did. A lot of the time when a mechanic screws something up people take it back to the same people. And most mechanics won't tell you if they screwed it up. And they will charge you. But if u take it to the dealer you might get the shop that screwed it up to pay for it. This especially sounds fishy since it started two days after the brake job.

[DiamondDW5]

Is there anything I could try doing before taking it to the dealer, such as inserting any fluids that I might be low on or something like that?

Oh and the code is P0304. Although you can't quite put your finger on the exact problem because you would have to see it, thanks anyway!

[lord flashheart]

you could try running a bit of quality injector cleaner but anything more would require some more expertise with diagnostics. you could go to the local parts store (oriellys, autozone napa) and they usually will look at it for you. wish i could help more. just out of sheer dumb curiosity, where are u from?

[DiamondDW5]

Philadelphia, Pennsylvania

[lord flashheart]

I was going to say if you were in the rockies I know a lot of people that could help you out. Sorry. Best of luck. Let us know what you find

[Huffer]

It's the car jerking, including steering wheel. I can be going 60 MPH and it jerks, sometimes it starts at 80MPH, which I rarely ever do 80MPH, but I had showed someone what I was talking about and instead of jerking at 60MPH, it did it at 80MPH.


If your steering wheel is shaking, then you have out of balance wheels/tires.

Brake rotors don't actually warp, they just get HARD deposits after cheap material gets too hot and basically becomes harder than a rock.

You have a misfire issue - when was the last time the car was tuned up?
http://www.obd-codes.com/p0304

[lord flashheart]

^ i dont mean to contradict you huffer, and im meaning this to be polite :D but i disagree with you, a bent CV shaft can do the same thing. usually it will cause viberation under acceleration, but if its really bad it will LITERALLY jerk the wheel as if some one was grabbing the wheel and jerking it to the right. it also made a creeking noise. 'i<3mysubi' had this problem really bad for a while. also brake rotors do warp.
if you get the brakes super hot say, coming down a long hill, and cool them down really fast, say you hit a puddle they do warp. but you are right, usually the deposit issue (thickness variation) that your talking about does happen and is offen mis-diagnosed as warping. it usually causes brake pulse as well.
http://en.wikipedia.org/wiki/Disc_brake

and he says it had a full tune up in nov. 2010

[Huffer]

I'm not disagreeing with you, but DiamondDW5 doesn't sound the most technically inclined, so making an online diagnosis of a "jerking" of the car is difficult at best. Yes, a bent CV shaft can cause those issues but it would more than likely cause those issues at all speeds, not just 80mph. Vibration that comes and goes is 90%+ due to a wheel being bent, unbalanced or both. Sometimes it's caused by a brake caliper seizing and sticking to the rotor as it's turning with the wheel.

I'd like to know what was covered in the November 2010 tune-up; for me a tuneup is oil +filter, wheel rotation, plugs AND wires, fuel filter and coolant. Brake servicing is new fluid, pads, rotors and slider pins regreased.

[DiamondDW5]

I got everything from the tune-up you mentioned Huffer, I got two new front tires with it instead of a rotation. As far as the brake service, I'm not sure because I got more work done because things were rusted. I will check and reply back in a minute with the details.

I have a question though, does this problem have anything to do with my transmission going?

[DiamondDW5]

Thanks for that website, I have noticed that it seems like everytime I take a trip (Less than 20 miles) my gas meter goes from Half tank to a quarter tank. There might be a leak somewhere or my gas meter thing is broke.

[DiamondDW5]

Yes, it is the actual car jerking. Disregard the steering wheel although I did say that at first. It lasts for about 20 seconds while driving and then stops. Then if I continue at a speed ranging from 60-70-80MPH it will continue to either jerk again for 20 seconds or the check engine will flash intil it becomes solid. I used to pull over and just restart the car but now I drive through it. The first 10 minutes of me driving fast, my car drives perfectly fine but then it starts that for some reason. I have not had the time to get it checked although I do plan on it, of course.


Sometimes I smell gas after I fill up my tank. It isn't on the inside of the car but if I roll down my window at a McDonald's drive thru or something, I will smell it really strong on the driver side and my tank is on the passenger side.

[TGX4776]

did you check the gap on your spark plugs? even though they are supposed to come pre-gapped occasionally they are off. we get a few people in a month with this problem and after gaping it sometimes goes away. I'd also say pull the plug from cylinder 4 and see what it looks like.

[lord flashheart]

wait wait wait. you replaced the front tires and not the rear? that is no bueno! that can cause some VERY serious problems. usually that causes the viscous coupler to bind up but ive heard of clutch packs slipping due to it. anyways. this sounds like a motor issue. im thinking maybe fuel delivery? i would like huffer to chime in and give some thoughts. unfortunately automotive diagnostics isnt like the show 'house' where if you think about it long enough you'll get some revelation or Epiphany that explains everything. its more of a troubleshooting/trial and error.

[Huffer]

I got everything from the tune-up you mentioned Huffer, I got two new front tires with it instead of a rotation. As far as the brake service, I'm not sure because I got more work done because things were rusted. I will check and reply back in a minute with the details.

I have a question though, does this problem have anything to do with my transmission going?


wait wait wait. you replaced the front tires and not the rear? that is no bueno! that can cause some VERY serious problems. usually that causes the viscous coupler to bind up but ive heard of clutch packs slipping due to it. anyways. this sounds like a motor issue. im thinking maybe fuel delivery? i would like huffer to chime in and give some thoughts. unfortunately automotive diagnostics isnt like the show 'house' where if you think about it long enough you'll get some revelation or Epiphany that explains everything. its more of a troubleshooting/trial and error.

First rule of Subaru AWD - you MUST match the tires, at least treaddepth, in order to preserve the life of the differentials.

If your transmission is on it's way out, then it can certainly cause the "jerking" you're experiencing because the trans is spinning at a rate, the engine is spinning at a different rate, and the torque converter is supposed to translate all of that. If that's dying, it's like a hand trying to grab a spinning top and letting go, etc etc.

Any more information about the car that you might have forgotten?

[DiamondDW5]

OMG! They're rules to tires too! Geez. Do car people know that because I asked for all four new tires at first but the man said the back was fine so I didn't bother.

[DiamondDW5]

wait wait wait. you replaced the front tires and not the rear? that is no bueno! that can cause some VERY serious problems. usually that causes the viscous coupler to bind up but ive heard of clutch packs slipping due to it. anyways. this sounds like a motor issue. im thinking maybe fuel delivery? i would like huffer to chime in and give some thoughts. unfortunately automotive diagnostics isnt like the show 'house' where if you think about it long enough you'll get some revelation or Epiphany that explains everything. its more of a troubleshooting/trial and error.

You said fuel delivery, meaning?

My grandfather said it feels like fuel isn't flowing properly somewhere. He says it feels like the car is running out of gas when he experienced it. Also, he said that there is a viberation on the gas pedal as well while it is jerking. My grandfather knows a little about cars and he suggest my fuel pump or catalytic converter may be going bad.

Do you guys feel as though I may need a catalytic converter or fuel pump?

[DiamondDW5]

I smell a strange odor like something is burning. At first it smelled like someone blew out a dozen candles but I don't know. I have been driving my boyfriend's car since I drive daily with my 8 month old to and from daycare on the highway.

[Huffer]

OMG! They're rules to tires too! Geez. Do car people know that because I asked for all four new tires at first but the man said the back was fine so I didn't bother.

If the tires are within 1/4" total diameter (at the same tire pressure) then you're ok. It's all in the owners manual.


You said fuel delivery, meaning?

My grandfather said it feels like fuel isn't flowing properly somewhere. He says it feels like the car is running out of gas when he experienced it. Also, he said that there is a viberation on the gas pedal as well while it is jerking. My grandfather knows a little about cars and he suggest my fuel pump or catalytic converter may be going bad.

Do you guys feel as though I may need a catalytic converter or fuel pump?

Fuel pump or catalytic converter - those are two widely different components and I doubt that it's something as serious as that. Can I ask if you have had the fuel filter changed, or run any kind of injector cleaner (you put a bottle of the stuff into the fuel tank, I recommend Seafoam or Chevron Injector Cleaner)? So, fuel filter, clean the injectors first before looking at a fuel pump. Depending on the miles, it's unlikely that your catalytic converter is going bad, but you might be due for new O2 sensors.

Any possibility you can give a list of what was replaced when (mileage) and total miles on the car now?


I smell a strange odor like something is burning. At first it smelled like someone blew out a dozen candles but I don't know. I have been driving my boyfriend's car since I drive daily with my 8 month old to and from daycare on the highway.

If you have any kind of oil leaks or any kind of foreign material landing on the exhaust system it can burn up and cause odd odors.

[lord flashheart]

You should add mass air flow sensor. That can cause a similar reaction. Sorry haven't been on in a while. I'm actually sitting at red Robinson waiting for a table lol. If you can post a video of the symptoms. And of under your car etc. The more info we have the easier it will be to diagnose the problem..

[jey]

Failing cat converter would smell like rotten eggs.
Irregular fuel delivery might be a bad fuel filter. It's a cheap and easy replacement and really part of regular maintenance anyway. We don't see a lot of fuel pumps go out in Subarus.

[DiamondDW5]

Sorry I'm so late but a video should be up in a few days. I did start a video of the parts under the hood. Trying to get the video with the Check Engine turning on while driving, but that's a lot harder. Lmao