Whenever i let off the gas or just ease on the gas the car bucks

[Kainnen]

I have a problem that occurs only after the car warms up and reaches around normal operating temperatures. Whenever i let off the gas or just ease on the gas the car bucks back and forth a bit. Vacuum leaks were fixed, new plugs and wires on the car, ECU caps replaced, throttlebody seals doneand new fuel filter.
It takes bout 5 to 10 min of driving before it starts and then it gets worst the longer i drive. It also effects the idle and it feels like its struggling to stay running sometimes especially when i come to a stop, it also stalls sometimes at idle. Its strange cause it just started happening all of a sudden after i got a tranny put on, and if im giving it gas you can't notice anything but if im at cruising speed and let off the gas it slows down more than it should and starts bucking back and forth a bit, enough to cause the shifter stick to move bout a cm. The tranny ended up being not so great so i had my old one fixed and put back on and the problem is still there. Any ideas on what could cause those kinds of symptoms.

 

[Kainnen]

When my old transmission went it leaked fluid on the clutch and the clutch ripped apart and scorched the flywheel. I got a new clutch disc and flywheel resurfaced but maybe the flywheel is messed up? Could it cause symptoms like this?

 

[Kainnen]

For the last month now ive had problems whenever i decelerate the car bucks back and forth and almost feels like im hitting the brakes, it can be fairly violent sometimes it seems to get worst the longer i drive the car. It does not start right away after a cold start it takes about 10 minutes before it starts acting up, also if i turn the car off and back on it seems to get better for a couple minutes. This also effects the idle when it starts acting up but doesnt appear to have any effect on acceleration, long as im giving it gas it doesnt act up(idle is fine till the bucking problem starts).

Ive been trying to figure it out for about a month now but running out of ideas, i have new TB seals, all vacuum lines replaced, ECU caps replaced, new fuel filter, wires and plugs. Ive tried unplugging the ISC and TPS but still had the problem. Im going to try swapping my spare ECU when i get a chance but any other ideas what could cause these symptoms would be greatly appreciated.

91 Laser 2.0L NT

 

[EagleTalonTim]

it sounds like the MPI relay located under the stereo could be going bad. that controls your fuel pump. It may be bad or have a faulty ground. It could also be that the car is running too rich. Is your CEL light on? If so, post the codes.

 

[Kainnen]

Only CEL ive had was for the TPS when i unplugged it, whatever the problem is doesnt seem to trigger a CEL.

 

[DarthBulk]

I've had this happen when the idle sticks on too high. When you try to decelerate by coasting, it is like you are bouncing off of a high idle...the drag on the car is trying to slow it below the high idle speed, but the high idle speed keeps bouncing the speed back up. Hence the bucking.
Do you have any high idle problems?

 

[Kainnen]

Nope idles almost perfect until this bucking occurs at what point i get a bit of idle surge but mostly it just starts to stumble and struggle to keep going, sometimes it even drops low enough for the car to stall.

 

[midnightwarrior]

i'm having the same problem, haven't figured it out yet

 

[Surfinggirl805]

Also had a similar problem. Replaced throttle body gasket, throttle positioning screw, ick motor and replaced a couple of other things. Later found out (after I had a timing belt pretty much come apart on me) that the exhaust values were bent (only in the 3rd cylinder).

Does anyone think this could be a similar issue?

 

[hubz91talontsi]

No, its probably his ISC

 

[1g dsm d22]

pretty sure is the MAF. u have CL on?
automatic or manual?

 

[TrevorS]

Also had a similar problem. Replaced throttle body gasket, throttle positioning screw, ick motor and replaced a couple of other things. Later found out (after I had a timing belt pretty much come apart on me) that the exhaust values were bent (only in the 3rd cylinder).

Does anyone think this could be a similar issue?

The timing belt coming apart would have been the cause of the valve damage -- not the reverse.

 

[Hesh724]

93 eclipse 4g37 , stick, when car is warmed up engine bucks and surges when slightly pushing gas and at the same point when letting off. if i let off fast or ride high rpm's it doesnt happen only when i am trying to go slow for the dumb neighbors walking their dog. does it do it, and makes me look like an ass . i have to ride the top of first and exauhst is to loud for that or i am at the bottom of second bucking around . pls help.

 

[burkgonzo]

I wanna bring this one back from the dead! I am having the same problem.

 

[darkiller_666]

I to am having similar part throttle issues. Very annoying for drive ability.

 

[swnkylaxplyr]

I'm having the same problem also. I get idle surge when I first start the car up and it warms up, but after driving, my idle will move to 1000-1200 rpms; so in my case the suggestion that the high idle is messing around with my on/off acceleration makes a lot of sense. Now just to find out what's causing the surge. I've tried everything except the TPS and IAC, so thats next.