Does your DSM jerk forward when switching between boost/vac?

[eboy0]

This is just a thing I've been wanting to know, but have no one to really ask around here who know anything about turbos.
When I'm driving and when I start boosting and whether I'm about to shift into a higher/lower gear, or just let off the gas at like 15psi, vac falls to 21, exhaust sounds 100% more bassy and the car nose "falls" forward hard enough if I wasn't leaning back, my face would be in the steering wheel.... Is this normal? I'm not sure if this is something mechanically wrong...
Any info/help would be appreciated.

 

[wimploki]

I recommend checking your Motor Mounts first. There are a total of four.

1. Near the timing belt side
2. Right above your Transmission
3. Front
4. Rear

This is just a thing I've been wanting to know, but have no one to really ask around here who know anything about turbos.
When I'm driving and when I start boosting and whether I'm about to shift into a higher/lower gear, or just let off the gas at like 15psi, vac falls to 21, exhaust sounds 100% more bassy and the car nose "falls" forward hard enough if I wasn't leaning back, my face would be in the steering wheel.... Is this normal? I'm not sure if this is something mechanically wrong...
Any info/help would be appreciated.

 

[the_skin_eater]

The sound seems to be normal....

But the jurking isnt.

I was driving my buddies tsi and boostin to 20ish, and there was no abnormal bucking between shifts.
Granted, you go from decent boost to none you will know, but it should never be like your saying.

In all the turbo cars Ive been in, never almost hit the wheel like you say....

Dont know what could be causing it though....

 

[xveganxcowboyx]

Shot suspension?

Poor shifting can exadurate the jerk as well.

 

[eboy0]

Shot suspension?

Poor shifting can exadurate the jerk as well.

The car did come with an upgraded suspension... could it be that the springs are too stiff? When I drive over the smallest bump I can feel it..?

 

[xveganxcowboyx]

I would think too soft would allow the kind of nose dive you feel. Too stiff shouldn't let it move that much. Or did you just mean that the weight shifts and not that the front of the car actually dives?

 

[romeen]

This is just a thing I've been wanting to know, but have no one to really ask around here who know anything about turbos.
When I'm driving and when I start boosting and whether I'm about to shift into a higher/lower gear, or just let off the gas at like 15psi, vac falls to 21, exhaust sounds 100% more bassy and the car nose "falls" forward hard enough if I wasn't leaning back, my face would be in the steering wheel.... Is this normal? I'm not sure if this is something mechanically wrong...
Any info/help would be appreciated.

Bizarre that you bring this up. My car started doing the same thing just yesterday. Runs fine while cruising and pulls hard once boost has kicked in. But the transition between boost and no boost (going both ways, i.e. accelerating and decelerating) is very abrupt. Feels like someone is hitting the brakes when car comes down out of boost. Off boost power seems noticeably weaker. Unfortunately I am healing from a herniated disc so it's difficult for me to work on the car but I'm not sure where to start on this one anyway.

 

[romeen]

The sudden decelaration is very similar to when you pop the clutch when push starting a car. I don't know if this might suggest a problem with the clutch or not.

 

[Deadly BlaZe]

This is just a thing I've been wanting to know, but have no one to really ask around here who know anything about turbos.
When I'm driving and when I start boosting and whether I'm about to shift into a higher/lower gear, or just let off the gas at like 15psi, vac falls to 21, exhaust sounds 100% more bassy and the car nose "falls" forward hard enough if I wasn't leaning back, my face would be in the steering wheel.... Is this normal? I'm not sure if this is something mechanically wrong...
Any info/help would be appreciated.

Is your car a 5 speed? If yes and this happens at 15 psi, i'm assuming you're at 3k rpm or higher at the time. If you take you're foot off the gas and not push the clutch in, you will feel like you hit a brick wall. It's completely normal. It's called engine braking. If you release the gas too abruptly you'll really feel it jerk hard; if you let off the gas slowly, you won't feel it jerk as bad. The vacuum is normal and the exhaust tone is normal too.

The car did come with an upgraded suspension... could it be that the springs are too stiff? When I drive over the smallest bump I can feel it..?

I don't think this has anything to do with your jerking problem. Although it could be the reason for why you feel every smallest bump on the road. That or your shocks are just shitty.

 

[romeen]

Is your car a 5 speed? If yes and this happens at 15 psi, i'm assuming you're at 3k rpm or higher at the time. If you take you're foot off the gas and not push the clutch in, you will feel like you hit a brick wall. It's completely normal. It's called engine braking. If you release the gas too abruptly you'll really feel it jerk hard; if you let off the gas slowly, you won't feel it jerk as bad. The vacuum is normal and the exhaust tone is normal too.

I don't think this has anything to do with your jerking problem. Although it could be the reason for why you feel every smallest bump on the road. That or your shocks are just shitty.

I have a M/T and while engine braking may be aggressive if decelerating out of higher boost levels this feels much more abrupt and is happening from very low boost levels. I can't speak for eboy0 but our problems do sound very similar.

 

[romeen]

eboy0, were you able to figure anything out?

 

[Deadly BlaZe]

I have a M/T and while engine braking may be aggressive if decelerating out of higher boost levels this feels much more abrupt and is happening from very low boost levels. I can't speak for eboy0 but our problems do sound very similar.

If that's the case then i would check motor mounts. Does the dash vibrate alot?

 

[romeen]

I have polyurethane x 4 but have had them for some time now. This just started so I don't think it's related to the mounts. But please keep the suggestions coming.

 

[Deadly BlaZe]

I have polyurethane x 4 but have had them for some time now. This just started so I don't think it's related to the mounts. But please keep the suggestions coming.

Well those mounts were definitely not made for comfort so I think you just found your problem. Even MachV says those mounts give the car a very rough ride. But if this just started happening and you've had the mounts for a while, then i'm out of ideas. Perhaps they need to be adjusted a bit?

 

[romeen]

Well those mounts were definitely not made for comfort so I think you just found your problem. Even MachV says those mounts give the car a very rough ride. But if this just started happening and you've had the mounts for a while, then i'm out of ideas. Perhaps they need to be adjusted a bit?

Agreed, they are not intended for comfort at all. But this does not feel like engine vibration/movement being transmitted to the rest of the car. It's more like putting the car in 2nd at 50mph and dumping the clutch (without the jump in rpms). And when boost kicks in it feels like a momentary spike to 20+ psi but my peak hold is only showing 11-13 psi (I turned down the boost since this started).

Anyway, thanks for the suggestions Arthur. Others, any suggestions are appreciated.

 

[chico904]

just wanted to chime in that I have an automatic and mine does the same thing, I never thought of it as anything other than normal though.

 

[vr4gasmtt]

I have the same problem, my cars a 99 gsx 5 speed, when i first bought the car it didn't do it, but then after awhile it started doing it, when I'm just cruising in 2nd and let off the thottle the car just feels like I slammed on the brakes, and when i step on the gas again it jolts forward, maybe not as crazy as almost hitting the steering wheel but it just feels awkward.

It makes me feel like a bad driver when I'm driving girls around .

My cars stock also, I'd like to fix this problem, at first I thought it was just how turbo cars felt like, but after driving my friends Saab turbo and my friends GST, it definitely doesn't feel the same.

The way I get around it though is just not let off the throttle at all, I let off very slowly up to a point where the rpms fall slowly... bugs me sometimes, because I always have to concentrate on it not doing the jolting. Its not as bad as I'm making it sound, but its definitely not a smooth ride.

 

[eboy0]

Very interesting that I'm not the only one with this problem, seeing as how some of our cars are modded, and like vr4gasmtt is stock, that rules out that upgrades aren't causing this problem. Anyone else have any suggestions? vr4gasmtt I know how you feel on the embarrassed part, sometimes when I look over my passenger is clenching the seat belt because they get thrown forward, literally....

 

[romeen]

You're right guys, it is embarrassing not to mention not at all conducive to good control of the car. The driver's around me probably think it's my first time driving a M/T. I feel a little better knowing that this is not a totally isolated occurrence. Hopefully someone knows what may be causing this.

 

[Deadly BlaZe]

Just out of curiosity, to the guys that are having this problem, does your car jerk back and forth repeatedly when you're not on the gas in the lower gears?

 

[gixx1000]

Funny that I came across this post. I'm having the exact same problem. The current list of things that I need to fix is that I only have 10in Hg of vacuum at idle and I have a leaky BOV. I thought one of these things must be contributing to the problem.

 

[romeen]

Just out of curiosity, to the guys that are having this problem, does your car jerk back and forth repeatedly when you're not on the gas in the lower gears?

No, I haven't noticed that. But now it seems even when I am off boost in 2nd or 3rd gear and I completely let off the gas the car abruptly decelerates. Like I said before, it feels very similar to when you pop the clutch during a push start except more violent because it's happening at 30 mph.

 

[Semprini]

mine started doing it after I put the 1g bov on, Im thinking the guy I bought it off of might have crushed it too much and under low boost its not enough to release. When it bucks I dont hear anything from the bov

 

[95autogst]

Now I'm just spit-balling here, but have you guys checked to see if your turbos spin freely? From my thinking, if your turbo isn't spinning easily, than whenever you let off the gas the turbo is going to want to stop and create a huge amount of back pressure (read: engine brakeing). This would also explain the abruptness when going from vac to boost, because the turbo is reluctant to spin.

Once again, just my .02 cents, so no hard feelings if I'm way off.

 

[eboy0]

Now I'm just spit-balling here, but have you guys checked to see if your turbos spin freely? From my thinking, if your turbo isn't spinning easily, than whenever you let off the gas the turbo is going to want to stop and create a huge amount of back pressure (read: engine brakeing). This would also explain the abruptness when going from vac to boost, because the turbo is reluctant to spin.

Once again, just my .02 cents, so no hard feelings if I'm way off.

Well I can easily freespin my turbine with my fingers, luckly my turbo has absolutely no shaft play whatsoever. I'll be doing a turbo upgrade pretty soon, along with a new manifold and whatnot, maybe that'll solve this issue, because it does seem like it's turbo related.