I've searched and searched and found nothing, however, I'm new to this board. So if this question has already been asked and answered, please excuse me for wasting your time and direrct me to the right place.

I have a stock 04 WRX sedan with a K&N drop-in air filter. Here's my problem. When I accellerate agressively up to 5000 rpm and abruptly let go the gas, the car jolts. It's a rather violent jolt. It happens in every gear, however 1st, 2nd and 3rd seem to be worse than 4th and 5th, maybe just because the latter are bigger gears. I've also noticed that if I use different fuel (higher/lower octane level) the problem still occurs, but at a different RPM (anywhere between 4500 to 5200). If I accellerate the same way but bring it up to 6000 rpm and let go the gas abruptly, the car smoothly decellerates, as it should.

I went to my dealer who had never heard of this problem. They contacted Subaru Technical Assistance who told them that the problem was due to my (stock) chrome tail pipes. They removed the tail pipes and guess what??? The problem is still there! Now, I'm not an engineer, but I could have told them that!!!

They are now supposed to go back to Subaru and find out what to do next.

Does anyone know about this problem and what the fix might be?

Another problem I've been having is this: say I'm in traffic, rolling slowly in 2nd gear at around 1500 rpm and press normally/softly (not aggressively) on the gas, the car jumps or jolts a few times before rolling smoothly. It doesn't take off smoothly. I've read a lot about grounding mods. Would my problem be a result of bad grounding? And before spending the time/money to do such a mod, is there a way to know if it'll work?

D-Rex.

 

My dad had an 02 outback and it had a reallly really violent jolting problem on deceleration. it was fuel related and fixed by warranty.

any subaru i have driven makes the jolting. i think its related to the awd and regular rubber engine and TRANSMISSION mounts. first...ask any other subie owner and they should say that the cars are notorious for driving like that. basically u gotta push the clutch in on deceleration to make the car drive smooth like an AT.

i would like to (after turbo kit granted there is money left over) purchase some sti transmission mounts and possibly engine mounts which is supposed to get the power down to the ground better than the crap stock ones.

in regards to the grounding mod....just do it...all it is is sanding paint down to metal to get a better contact. hehe. took me 10 minutes.


good luck

 

What I meant about changing the octane level is that different gas suppliers have different octane levels for their top-end fuel. I live in Montreal. There's Shell who offers 92 and Petro Canada who offers 94. Both of them seems to react the same, I'd even say that Shell is superior. However, there's a noticeable diff between Petro or Shell and Ultramar 92. The car reacts differently. And in my case, the jolting seems to be less violent with Shell and at a different rpm.

As for the fact that I shouldn't worry about my problem, it's difficult to live with it when I had an 02 and never had the problem. Also, if I release the gas at 6000 rpm, there's absolutely no jolt. I would think that there would be more pressure in the engine causing a more violent jolt. The reason it annoys me this much is that I often shift around 5000 rpm and for that fraction of a second when I let go the gas and press the clutch, the car jolts. It's just annoying. It feels like I'm popping it out of gear without pressing the clutch. Don't get me wrong, I absolutely adore this car and wouldn't trade it in for anything, but IMO this is a problem and Subaru needs to fix it.

Also, to reply to Antdiesel3, you say "it is not good to let off the gas abruptly, which slams the throttle plates closed, on a turbocharged vehicle". Isn't that the purpose of the BOV? To let out the excess pressure? And why only at 5000 rpm and not above.

I still didn't get a reply from the dealer and as soon as I hear something, I will post Subaru's response. In the meantime, I can't help but think that there's something wrong.