Fixing Jerk on Acceleration

[Evan.]

Here's the setup:

1999 Civic EX
B16A3 Motor
4.785 Final Drive in Si Tranny

Symptoms:

In any gear (1-5), when I let off the gas pedal quickly (don't feather it / slowly let off), the car kind of "bucks" back and forth very noticeably. It's most aggressive in 1st gear and least (but still noticeable) in 5th gear. At the same time, if I barely press on the gas pedal (as in stop and go traffic) I get a similiar reaction.

I've determined that it's the motor mounts, namely the rear mount being the main issue. I can replace the rear mount with an OEM Honda mount just fine, but i'd rather replace it with something a bit more durable since it's under a higher load due to the final drive set / etc. However, at the same time I DONT want alot of rattling that comes with aftermarket mounts. So here's the options I've been debating:

A) Get energy suspension inserts on top of the new mounts.

Notes: Alot of people are complaining about aggressive rattles.

B) Get just the Hasport rear mount

Might be too stiff?

C) Get ITR replacement mounts

supposively more beefy than others but retaining stock comfort?

D) Just replace the mounts with OEM Si.

 

[eskateboarding7]

I believe I have the same "jerkiness" with my RSX. Motor mounts you say huh? I might have to try that if it solves your problem. I've just always read that Hondas are like that and to just put up with it Let me know how it goes.

 

[Black!e]

i think thats normal? ehh cuz i have the same jerkiness when i do that

 

[mixwell]

if you get hasport mounts, get the ones with the street bushings, not race or they will be too hard and your car will vibrate too much.

 

[JohnS.]

I have the same problem. 90% of my driving is city driving too so especially in traffic and such, I'm always in 2nd and I gotta let off the gas, coast, press the gas slightly, coast, etc. My car jerks really bad. I push in the clutch to avoid it .

I'm thinking OEM mounts might be too soft... ES will be too harsh... Try ITR ones...?

 

[devo1104]

what sort of shifter bushings do you have? when i replaced mine i noticed that it was harsher when i used the clutch

 

[andrewmrtnsn]

mine was doing the same thing.. believe it or not it was the IACV. it bucked like a SOB til i got it replaced

 

[CivicMafia]

OEM SI mounts, The guy who had mine i belive replaced with some race mounts ( Idk what kind ) But you can feel the can shake specially when rev'ing ( not real bad though )

 

[mymmeryloss]

itr sounds best to me

 

[ryanM]

evan, when you go from WOT acceleration to 0 throttle, especially in 1st gear, the engine braking that occurs is very similar to what you would experience if you slammed on your brakes at 50mph. of course your car is going to buck like that. if you dont want it to, push your clutch in when you let off the gas abruptly

 

[phong3992]

It might be the IACV.. I had that same problem.. it was jerking a horribly in 1st gear..

Check that sensor..

When the car is in neutral trying going slowly through the revs.. if it starts to bounce in between.. 1 - 5 thousand RPM.. its probably your IACV... push the throttle very steady through rpms thats how i knew it was my IACV..

 

[Evan.]

thanks guys...

I know it's partially due to the wear and tear on the mounts but at the same time I'm sure the final drive set and "torque" of it doesn't help..

 

[97GreenEX]

Same happens to me. But I have polyurethane mounts...And yes it vibrates like a mofo

 

[ryanM]

its NOT a problem

thats NORMAL

its like saying "why does my car slow down when i let off the gas?"

 

[Evan.]

right, but i'm saying it decelerates hard. I think it's due to the final drive and short gearing though.

 

[ryanM]

yes, that will amplify the effect

more power will also

if you want it to go away, less power and longer gearing.

 

[SlowTEC]

I'm sure bad motor mounts don't help, but like Ryan said, you're going to get it when you abruptly let off the gas, especially in low gears. Now if this is something new, like it's gotten worse recently, I would go ahead and replace those mounts ASAP and see if it gets better. Just think of what you're motor's doing when you accelerate, it's trying to turn faster, but the car's resisting. When you let off it's the opposite, the motor's trying to stop turning, but the car is making it continue to. It's a reverse of force, causing the motor to "rock" slightly. If you've got bad mounts you're going to feel this more.

 

[SlowTEC]

Oh, and ITR rear mount sounds like a great idea. I've got some Energy poly inserts waiting for me at home right now. I've heard they're pretty stiff, but my Civic isn't going to be my daily driver anymore, so it's alright .

 

[NFR_AP2]

yeah i had this same exact problem. its the IACV

 

[devo1104]

i have the energy in my car, it really isnt that bad. i thought it would be more like the american muscles that have 1000 hp the way most of these ppl talk about it. in actuality, it just vibrates a little at idle and you dont really feel it once you get the engine going.