Akward Acceleration Experience

I've been having a few wierd things go on with my car. Two of them are somewhat related.

The first issue is when I am going very slow, anywhere from 1-10/15 mph, when i let off the accelerator, the car has a huge jerk, which i think may be my engine mounts (i am about to get energy susp. inserts put in) When i hit the gas i feel the engine "hit" and when i let off, it jerks back.

The other maybe somehwat related issue was today, i was driving and had the car in 2nd I believe. I floored it for a sec, it hit about 5000 rpm, and the gas was still pressed down, yet the car stopped accelerating. It was very weird.

If anyone has any ideas to what this could be, post up for me.

The timing belt is about 15000 overdue as well, i dont know if that could have anything to do with it.

I have searched for related issues in the forum yet couldnt find anything due to so many, so if something like this had been previously addressed, dont start trippin.

Thanks


(98 GST)

get the tbelt done! ever time you start your car you are risking a lot of money since you will trash your whol head if the tbelt slips. get the water pump, balance shaft belt and both tensioners done at the same time since any one of them can trash your tbelt if they go bad.

fuck the Bshafts!! get rid of those things!

the 10-15mph thing sounds like any other stick car. there is just a bump when you let go of the gas and don't put the clutch in at that speed.

as for the accel dropping off at that speed, i'm assuming that you are stock. if that is the case there are 3 things that come to mind:

1. the t-25 starts to run out of breath at that rpm.

2. the stock BOV leaks over 12psi

3. there could be a couple of places that a boost leak may be happening. the intercooler pipe connections [all of them] and also where the BOV connects.

the reason could be any of the 3 or a combination of both. check it all out.

hope that helps...

yeah that's normal for the car to jerk like that, does that in any stick that i've ever drove. i think i read somewhere it's because the throttle plate closes as soon as you let off the throttle and that's what causes it to jerk for a second. as for the other problem, BoostedSpyder is right. the t-25 isn't much good for 5,000rpm's +, and you could even have one or more boost leaks.

alright, good deal on the slow accel thing

and no i am not stock (sig)

apexi exhaust, dp, gred bov, icp, intake

but still it wasnt a normal turbo thing to where it doesnt have much power past 5k.

its like it didnt move at all
it doesnt happen all the time, that was the only time its happened.
i just floored it, kept the pedal at the same place, and all of a sudden, it stayed at a constant speed, as if no gas was going in anymore or something, or no air.

another related thing is sometimes (especially today)
i will be going at any speed
ususally mid speed (30-50) and ill have the gas pedal down, anywhere from 1/4 to all the way down, and keep it down, but the car seems to slow down for a 1/2 second - 1 second or so, and then gets back. i dont know if it "slows down" but its like it looses boost for a second then regains it. This seems to happen a lot when my ac is on. It's like this, "stuttery" throttle feel. it will sort of feel like boost is going up and down eveyr once and a while.

boost leak?

i hear some whistling coming from the throttle body when the car idles.

i dont have a good way to check it because i dont have a air tank, but i can take it somewhere if thats what it sounds like

If you press on the gas and idle goes up or reacts with your peddle (e.g. the engine is moving) and the vehicle doesn't then you're getting clutch slippage.

If it's vacuum related then get carb cleaner. Spray it around the engine (just not the intake itself). If the engine idles spike then you've got a leak somewhere. It's pulling in the carb cleaner and adding it to the fuel like additive.

You could also get an automotive stethescope and put it around the engine area. Listen for something that sounds like a whistle, remembering where air flows through the engine (e.g. the timing belt area wouldn't help).

Without further info though I just couldn't start to help.

If there was a belt problem, you'd know it. Just inspect the belts for cracks etc. If they exist then they need to be changed before you can do any further research.

If the vehicle is jerking then you may be incorrectly shifting or letting out on the clutch or have a crack in the flywheel. It's hard to deduse something like that without having it in front of you.

well i know what a clutch going out feels like, trust me. i think most people with modded dsm's and a factory clutch have.

and im not "incorrectly shifting". that issue is only when the clutch is already out and im just pressing the gas and letting it out some, and the car will jerk as if not as much fuel was going in or something. hard to explain. im confused, i guess ill just take it to this jap perf shop down here. thanks

it sounds like you have a boost leak at the throttle body. sometimes they can come and go so youll notice it somedays and not notice other times. if you dont have an air tank then try the carb cleaner method, it wont show leaks that only happen under boost but it's better then nothing

Cant you just use a bike pump? http://www.vfaq.com/mods/ICtester.html

Yes you can use a bike pump..... It's a LOT easier to use a compressor with a regulator on it....
I tried the bike pump but really had to pump like a mo-facky just to get pressure...