[40thmustanggt]

when im going down a hill my car starts to some what buck around 2k and up like its trying to idle down but speeds it self back up? hard to explain but maybe you all know what im talking about. im thinking its back pressure it never did this untill i installed the slp lmII's its been doing this for awhile but i was just thinking maybe a dirty maf.. any ideas??

 

[SilverGT04]

my car has been doing the same thing but idk wen it started aorund 2200 to 2000 it starts to kind buck back and forth till u drop it into lower gear

 

[40thmustanggt]

my car has been doing the same thing but idk wen it started aorund 2200 to 2000 it starts to kind buck back and forth till u drop it into lower gear

yep.. im thinking its just back pressure but i want to be sure.

 

[40thmustanggt]

:dunno

 

[Hasselm8]

when im going down a hill my car starts to some what buck around 2k and up like its trying to idle down but speeds it self back up? hard to explain but maybe you all know what im talking about. im thinking its back pressure it never did this untill i installed the slp lmII's its been doing this for awhile but i was just thinking maybe a dirty maf.. any ideas??

Is your car automatic or manual?

 

[40thmustanggt]

Is your car automatic or manual?

manual

 

[HMUSN]

what gear are you in and at what speed (and your rear gears are ? )

 

[40thmustanggt]

what gear are you in and at what speed (and your rear gears are ? )

4.10's 40mph or below 4th or 3rd gear anything around 2200rpms below

 

[HMUSN]

that's odd.

it sounds like your rpms are within good range.

 

[40thmustanggt]

that's odd.

it sounds like your rpms are within good range.

i dont remember it doing it before the 4.10's or the catback. im thinking its back pressure but im not sure? its like it wants to idle down but it starts bucking

 

[HMUSN]

your idle is controlled by your foot for the most part since you have a stick.

at 2200 rpms at 40 you shouldn't be bucking.

 

[40thmustanggt]

your idle is controlled by your foot for the most part since you have a stick.

at 2200 rpms at 40 you shouldn't be bucking.

its only when im going down hill off the gas not on it.. i thought i said that sorry

 

[Hasselm8]

your idle is controlled by your foot for the most part since you have a stick.

at 2200 rpms at 40 you shouldn't be bucking.

+ 1, this should not be happening if you drive stick, your throttle response is in your foot. Do you have an aftermarket throttle body? If not did you clean your iac and valves in the throttle body?

 

[Hasselm8]

Are you engaged in a gear when going down hill?

 

[40thmustanggt]

+ 1, this should not be happening if you drive stick, your throttle response is in your foot. Do you have an aftermarket throttle body? If not did you clean your iac and valves in the throttle body?

no.. nothing has changed this started after the 4.10's and catback.. it only does this going down hill with my foot off the gas? would a video help?

 

[40thmustanggt]

Are you engaged in a gear when going down hill?

yes

 

[Hasselm8]

Sometimes when you are engaged in a lower gear and going down hill it will buck by itself, if you want to stop that just shift into a higher gear. YOu might just be riding the clutch down the hill without realizing it. What I usually do if Im going downhill and not using the gas, is just leave it in neutral. By the way the vid would help if you have one.

 

[40thmustanggt]

Sometimes when you are engaged in a lower gear and going down hill it will buck by itself, if you want to stop that just shift into a higher gear. YOu might just be riding the clutch down the hill without realizing it. What I usually do if Im going downhill and not using the gas, is just leave it in neutral. By the way the vid would help if you have one.

i'll get one today.. my foot isnt even on the clutch when it doea this

 

[1crisis]

I put in 4:10s in January and it is doing the same thing as yours. I get the bucking (minor but annoying) when I let off the gas in 4th below 40mph. I thought it was the tune that was installed in the car at the same time but I think it is the gears. When the gears are installed, an adjustment is made for backlash which keeps the gears etc. tight during deceleration. I think if it is not adjusted properly and there is too much play, we get the lurching while we slow down. To eliminate the other things like intake/tune/engine as a possible sorce of the problem, find a empty road, drive at 40 mph in 4th, turn the ignition off (dont lock the steering wheel), dont put the clutch in and leave it in 4th, and let it slow down. I think if its the rear end, it will still lurch. Im still trying to figure this one out myself. Keep me posted!

 

[1crisis]

Well I just went out and disproved my own theory. With the motor shut off, car in 4th gear, at 40 mph and slowing, the thing slowed without lurching. It does not seem to buck or lurch while decelerating in 3rd gear. Im baffled.