Car jerks when letting off or barely pressing gas pedal.
 

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. Any ideas?

Thanks.

Re: Car jerks when letting off or barely pressing gas pedal.
 

Maybe a sticky throttle cable or throttle body plate? You might start by cleaning the throttle body and checking the throttle cable adjustment. How's the throttle pedal acting?

Is the CEL ON? Another possibility might be a faulty TPS.

Re: Car jerks when letting off or barely pressing gas pedal.
 

There are no CEL on at the moment. The butterfly valve moves freely with no "stick" toward the bottom. Everything was cleaned up when the swap was done < 1 yr ago.

I have NOT checked the cable adjustment and will definetely make sure it's within specs.

Any other ideas?

Re: Car jerks when letting off or barely pressing gas pedal.
 

Bad Mounts? or maybe Mounts are too stiff?

Re: Car jerks when letting off or barely pressing gas pedal.
 

Right, I do have a feeling the mounts are the cause. Now would it be the torque mounts (front two) or the rear mount that prevents the most engine movement?

Re: Car jerks when letting off or barely pressing gas pedal.
 

This makes a lot of sense. Also check whether the driver's side upper mount is ruptured. It will be obvious by inspection whether the two front insulators are bad.

Re: Car jerks when letting off or barely pressing gas pedal.
 

True, I'll take a look tonight. However which attributes to movement more, the torque mounts being broken or the rear mount?

Re: Car jerks when letting off or barely pressing gas pedal.
 

You'd definitely know if it was a engine mount. You can feel the engine moving if its bad enough.

Re: Car jerks when letting off or barely pressing gas pedal.
 

i would think if you were bucking like that it would be your rear mount. my car also does this but only in first gear but i think its cause my mounts are very stiff plus im also using the two factory stabilizer mounts on the front of the block so all in all im running 5 mounts

Re: Car jerks when letting off or barely pressing gas pedal.
 

I had the same problem with my B16A in my EG hatch i replaced the TB with a 68MM omni power TB and it stopped so i came to the conclusion that it was just a stick throttle body plate....try cleaning it? or replacing it?

Re: Car jerks when letting off or barely pressing gas pedal.
 

from an initial look underneath, the AC side torque mount is definetely torn. The driver's upper is fine. I'll check the other torque mount and the rear, but a couple questions.

Since I'll be replacing the one torque mount I'd rather go something a bit stiffer. I'd get the AVID torque mounts, but here the vibration is too much for street applications. So should I get the ES inserts or do the ghetto but true 3M Window Weld filler?

Re: Car jerks when letting off or barely pressing gas pedal.
 

Most definintely the motor mounts. Change em' out and you'll immediately notice a difference. Much much smoother!!!

Re: Car jerks when letting off or barely pressing gas pedal.
 

If the car is in neutral and you rev it through the RPM range does it rev smoothly? or does it act the way it does when you are driving it? That's a good way to tell if it's a TPS sensor problem or something mechanical. If you had a sticking throttle plate or body you'd know it! You could feel it in your pedal.

Re: Car jerks when letting off or barely pressing gas pedal.
 

it has nothing to do with throttle bodies, motor mounts, or anything of that nature what you are talking about is the motors has sudden jumps in torque and jolts you back and forth. i think this happens do to your clutch not being sprung or something of that nature. my car does the same and i too have b16 with lsd and 4.7 final with new hasport mounts street, avid torque mounts race, and a torque damper bolted behind the head and i still get those jolts from time to time, i have learned to be very easy with the gas pedal and i suggest that when it starts jumping just shift up to the next gear.

Re: Car jerks when letting off or barely pressing gas pedal.
 

Thanks for the replies. I'm just going to eliminate all the possibilities:

1) Clean the throttle body / adjust the cable

2) Replace broken mounts - I already know the one torque mount is broken.


But here's my last question. In regards to the broken mount, I want something a bit stiffer so that I don't have to replace it so often. I hear AVID is too stiff, so I'm thinking either ES inserts or the 3M Window Weld?

Re: Car jerks when letting off or barely pressing gas pedal.
 

you will beable to feel a broken mount and it will make noises if the car just jerks when the gas is pushed and released is has to do with the fast idle solidoid Some times there is a little turn screw inside that you must turn They have a tedency to turn loose i had the same problem with mine fore nearly a year after>... Is it only after the car warms up after youve been driving it awhile? Thaat will solve your problem

Re: Car jerks when letting off or barely pressing gas pedal.
 

My car was doing the same thing last night, I got a CEL (code 15) and i had to fix some wires in the dizzy...doesnt do it anymore. Dunno if this helps, just my .02.

Re: Car jerks when letting off or barely pressing gas pedal.
 

That doesn't it like. The problem is not affecting by whether or not the car is hot / cold.

Thanks for the suggestion, however I think you're car was affecting by the CEL.


Also, for the guy that said can you feel it in neutral when you rev? Yes I can.

Re: Car jerks when letting off or barely pressing gas pedal.
 

i kinda have the same problem and i notice i can rock the motor just a bit. im pretty sure its the mounts on mine

Re: Car jerks when letting off or barely pressing gas pedal.
 

This happens to me but only in first gear. In happened on my other car so I assumed it was kinda normal? If I take it to like 2000+ in first gear and just let off, the car jerks back and forth as the RPMs drop, and it eventually stabalizes after a few seconds when it's at idle speed (but still moving as its in gear).

Is that normal? Sorry for the thread jack. it doesn't do it in any other gear.

Re: Car jerks when letting off or barely pressing gas pedal.
 

Re: Car jerks when letting off or barely pressing gas pedal.
 

exactly , my wife had this same problem with her 2003 ex, the clutch fluid was a lil low, and when i took it to the dealership they took the tranny out and the clutch was just worn from wear and tear m lil gabs when you engage the clutch i guess , not hramful , but hte longer you go the faster your clutch dies

i know this is a late post but, could be that? worn clutch

Re: Car jerks when letting off or barely pressing gas pedal.
 

i had the same prob with my em1.....tps sensor

Re: Car jerks when letting off or barely pressing gas pedal.
 

im currently having a tps cel along with iat cel but i dont notice any of those problems, i belive it to be a mount id do the 3M filler see if that works and replace the broken one, if that dosnt solve it like someone said it could be a clutch issue, your clutch fluid full? how old is the clutch?

Re: Car jerks when letting off or barely pressing gas pedal.
 

WOW! what a guessing game this thread has turned into, buddy the cause of your problem can be alot of things! your explaining of the situation is very good and sounds exactly like the issue I had and for you not to go through a very very long list of parts I recommend you finding an b16 running car from any friend etc! change most of those parts listed above from the donor, go and change them one at a time, try the ignition parts first by swaping the dizzy,wires,plugs,tps,ecu than go with the fast idle valve and Iacv, then try the mounts,remember try them one at a time so that you can really pin point what your problem is! this idea shouldnt take too long even if it turned out to be the very last part you try! and it will save you a shit load of cash trust me.