My car has a funny judder wen accelerating through the gears. Someone said might be prop shaft but have just changed it and made no difference. Any suggestions or anyone had the same problem?

What modifications does the car have?

Just a hks induction kit, cat back exhaust and forge dump valve

Has it been mapped for the mods?

My first inclination was a VTA dump valve as they can (but not always) cause hesitation after a gear change due to all the air that would normally be recirculated getting vented instead. Do you have the standard recirc valve you can put back on to test?

The car be doing it pretty much since I brought it it wos standard when I got it so do still have the origanl valve. Took it to Subaru near me and they jus charged me a bomb and not really knowing what it was. Thought it might be gearbox but they dropped the oil then dint really say anything else Then said the next step would to be the prop shaft. Car hasn't been mapped well as far as I know

probably a dumb question but have to had a look at the spark plugs as one or more of them may well have gone bad does the car "pop" (well more regularly than normal) as this can be a good sign that the plugs are knackered or on their way out.

 

i'm no professional but thought it might a simple thing that is reasonably easy to look at/ sort.

 

or it could quite well be over/underboosting

I would put the original valve back on just to test... at least rule it out for sure and should only take a few minutes to swap over. Does it only happen when on boost? Possible failing fuel pump? I'm not overly clued on here as much as a lot of other people :D

The car do pop a lot wen I'm slowing down and come of the throttle. I had it serviced wen I got it about 9 months ago oils plugs cambelt the lot And it got full service history. It hard to explain makes the car shake you can see the needles shake about wen it doing it.

i had the same trouble with my 99 forester when pulling off and also in second then was ok?

 

never fixed it as i sold it but I put it down to clutch judder?

Worn engine/gearbox mounts can contribute to this