car judder!
 

bit of a strange experiance.some times when i hit or approach a certain speed,lets say 100mph the car will hesatate and judder then take off again.its quite a powerful shudder.this seems too happen more under hard accelaration as opposed to gradual smoothe acceleration.i thought it may be along the lines of the ecu or fueling but am reading about engine knock and knock sensors,subarus are fairly new too me so im still learning,i have no warning lights on the dash,no smoke and the engine just sounds normal to me.any thoughts or ideas on this much appreciated.its going in the garage on friday so will ask the mechanic to check but was wondering if there would be any more things i could be looking at myself,thanks,ryan.

Whats the spec of the car Ryan?

thanks for the reply.its a 2002 jdm sti.it has a full decat exhaust,fmic,hks cone.im unsure as to any other performance modifications including an ecu remap as all the parts were on the car before i got it.i shipped it in from cyprus last month.apart from that the car runs completely fine,pulls well in each gear,no smoke or strange noises.fairly good fuel consumption.thanks again,ryan.

I had this at 2 levels and for me 1 problem was the car hitting boost cutoff turned out to be my waste gate pipe had popped off

The 2nd judder was because my turbo wasn't seated right

thanks for the reply,mine also seems to be on boost but its only at or close to said speed.nothing like that happens in any of the gears building up too it.cheers,ryan.

Might be worth getting it checked over mate, just with you saying its recently been imported.

Yes mine was the same in 5th gear and sometime at the top end of 4th gear

anything im perticular to ask the mechanic to look at with these mentioned symptons?icheers,ryan.

surely if a pipe had popped off it would affect boost in all gears?cheers,ryan.

Only effected me in gears 4 and 5, a normal mechanic won't know jack all I doubt, you need to check your boost lines mate and check everything is connected and no disconnected ones

Also check you don't have one of those nasty manual boost controllers in

Thanks for the heads up.ive listened to a few videos on YouTube and my car sounds nothing like them which I'm fussing is a good thing and yeh I'll have a check around the engine for loose Moses etc.its got an electronic boost controller fitted.thanks for the reply,Ryan.

electronic boost controller! - there is your problem then, its over boosting and guessing its not mapped as the boost is hitting the cut off limit on the ECU

Overboost fuel cut is like throwing an anchor out the window rather than a judder though

So you think that could be a possibility?ive actually been trying to get hold of a well known mapper to get it set up for being in the uk(fuel Ron etc) but after one email never heard anything back,thanks for the reply,Ryan.

If you doubt the controller, turn the boost down! What's it set for?

It does judder I had it on mine like, really bad judder aswell if you drive like a miss daisy and let go of the peddle quickly it doesn't, but if you keep the pedal down it does judder badly

And I can see why because you constantly are hitting and dropping above and below the ECU thresh hold

But yeah the answer to your question is yes I believe a map will sort it out, your car won't be running too good with out it considering what you have on there

Get a mapper and get it right :)

Fair enough, I'm only speaking from my experience. I guess I've been quick to lift my foot once it cuts the fuel off.

Same here too mate, I let off go quick at first but I think curiosity got the better of me to see what would happen lol

thanks for l the replys.hopefully a decent map will sort it then.i shall continue to try and get hold of a certain mapper and go from there.thanks again,ryan.