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Jerky acceleration/deceleration. Help!


Scrubb

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I've noticed recently that my car would be jerky when changing from no throttle to accelerating in low gears (1-4) and also when coming off the throttle and decelerating. Also when in gears 1-3 when trying to drive at a constant speed on a flat surface it will jerk.

 

Another person on the internet had a good description:

 

".... excessive rubbery jerkiness every time you accelerate or decelerate. I mean the second you depress the accelerator pedal or the second I decelerate, it feels like you are being chain-pulled by another car. It's like a double or triple bounce.."

 

It never used to do this when I first got the car, but is getting increasingly worse the more I drive it and I want to nip it in the butt before it gets too bad!

 

Car is a 1981 Mitsubishi Lancer EX, 1600, 5-speed Manual and has done roughly 93,000 genuine Km's.

 

I have replaced the clutch making sure to machine the flywheel and replace release bearing. I also replaced the gearbox mount while I was at it. I rotated the driveshaft while it was in gear and it rotated a bit, but I've not got a clue how much is too much and that's about as far as I can diagnose haha

 

Can anyone give some clues on where I can look to find the problem?

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first or reverse.

see if you can look underneath while someone rocks it back and forward- id be looking for

 

worn upper/lower susp link bushes- look for the diff rotating as the car stops moving

diff problem- if the car moves a bit but the driveshaft doesnt turn, might be in the diff, (i had a car that the spider gear pin wore a slot in the carrier and did exactly what you describe)

driveshaft- look for worn u- joints

open the bonnet and see if the engine moves around a lot ie if it has a broken engine mount

if the car moves a fair bit, and the driveshaft turns, it might be a gearbox problem

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first or reverse.

see if you can look underneath while someone rocks it back and forward- id be looking for

 

worn upper/lower susp link bushes- look for the diff rotating as the car stops moving

diff problem- if the car moves a bit but the driveshaft doesnt turn, might be in the diff, (i had a car that the spider gear pin wore a slot in the carrier and did exactly what you describe)

driveshaft- look for worn u- joints

open the bonnet and see if the engine moves around a lot ie if it has a broken engine mount

if the car moves a fair bit, and the driveshaft turns, it might be a gearbox problem

 

can check by wiggling the driveshaft

 

 IF it moves up and down, then the pinion bearing is on its way out.

if it rotates more than a 1/2" then the back lash is out

 

Awesome. This sounds like a great place to start. Will try these things tomorrow and report back.

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Put the car in gear tonight and pushed it back and forward and I don't think it moved more than an inch.

 

The weather is pretty crappy so couldn't do much but I attempted to move the driveshaft side to side and up and down and it felt pretty solid, which brings me to another problem I had forgotten about. When depressing the clutch pedal there is a clunking sound sometimes when the clutch engages while in gear. I'll have to jack the car up when the weather is better to play around a bit more with the driveshaft and look at diff movement.

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  • 2 weeks later...

So, in the weekend I replaced the coil and the engine is running much smoother and the jerky behaviour when coming on and off the accelerator seems to be a million times better and almost disappeared, but it still jerks alot when decelerating in gear. It mostly happens in 1-3rd gear, I don't notice it in 4th and 5th.

 

Should I maybe be looking at getting the gearbox rebuilt? Second gear is a bit crunchy. Can anyone give an indication of the cost of this these days?

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