new engine jerks just above idle??

[robbo_yobbo]

Just had a VCT engine installed into my AU and now it feels like Im flying an F16 fighter jet compared to the sluggish 800thou+km engine which was in it, but there is one annoying thing it does now which bugs me (its also just been converted from auto to manual)

when im driving at a constant speed with my foot slightly on the throttle, the engine jerks like it doesnt know if its supposed to be injecting fuel or not......
If I put my foot down a bit more its fine or if I take my foot of its fine too, its only when im trying to maintain a constant speed. the lower the gear, the more noticable the jerking (thats probably because the higher gears absorb the jerk)
Is this normal??? could it just be the computer needs time to relearn itself?? Any ideas what the problem could be??? cheers.

[SIKSIX]

This is sorta out of no where but maybe check that the engine mounts are doing thier job.

[onfire]

Iv noticed my AU1 4.0l does that. I actully read on here somewhere, to drop it back into third. When say cruising in a straight line through suburban streets under 50km/h. Try that.

[Stav]

Mine does that gently with the auto..I am thinking it may be the tps readings at light pressure arent registering right.

[RG]

Sounds like backlash, most do it, especially manuals.

[robbo_yobbo]

Originally Posted by GreenEL

Sounds like backlash, most do it, especially manuals.

What is this? any way to stop it or at least minimise it?

Originally Posted by onfire

Iv noticed my AU1 4.0l does that. I actully read on here somewhere, to drop it back into third. When say cruising in a straight line through suburban streets under 50km/h. Try that.

I did notice that too, but I had to be in 4th at 60kph to reduce it if i have light pedal pressure

Originally Posted by useless

Mine does that gently with the auto..I am thinking it may be the tps readings at light pressure arent registering right.

This sounds like the sort of problem I thought it could be, next problem, where to from here???

Its litteraly like when im just lightly touching the pedal, the car gives the engine fuel, and then decides its too much so stops all together, then decides it needs more fuel so gives it another quick burst, and then stops again and so on and so on....
its almost as though its not capable of injecting a minimal dose of fuel, so just gives it larger doses inconsistantly..... could it be a fuel map issue even, or am I barking up the wrong tree?

[Stav]

I dont know man.Ive noticed more since ive been told to drive my new box in economy mode.Not so much in power.But power wrecks my box.

[RG]

You would have to talk to a driveline specialist about that one.

[XR6-VCT-2000]

I have exactelly the same problem in mine (but mine is an auto), and i dont think its a problem ! - it just the revs are too low to push the car along imo , mine does it if in 4th and slugging along slowly around 60kmph . Years ago I put a 4 speed auto from a mustang into my old XE ( was a carby driven car too , not fuel injected - no ecu etc etc ) , and it did exactelly the same thing in 4th in my XE too if i drove it in 4th around 60kmph (that auto was almost identicle to these auto's too, the ford FIOD 4 speed auto )- imo it's almost like trying to push the car around on idle !. Personally in that car - and this 1 - i didn't/don't use 3rd unless on hwy's etc etc unless im doing around 100kmph .

[XR6-VCT-2000]

Originally Posted by XR6-VCT-2000

Personally in that car - and this 1 - i didn't/don't use 3rd unless on hwy's etc etc unless im doing around 100kmph .

Ooops , typo error - 4th gear i meant sorry .

[robbo_yobbo]

Originally Posted by XR6-VCT-2000

Ooops , typo error - 4th gear i meant sorry .

I dont have the problem in 4th and 5th as the higher gears absorb the jerking, its only predominant in 2nd and 3rd (im sure it would be the same in 1st if I tried to keep a constant speed too), the lower the gear, the more noticable it is.

[XR6-VCT-2000]

Originally Posted by GreenEL

Sounds like backlash, most do it, especially manuals.

Oh i got ya , sorry , it could be as GreenEL stated then ! .