mk4 20v turbo, wierd noise on acceleration

[running with scissors]

hiya all

just a query , i got me a t reg 1.8t golf in jazz blue with privvy glass and a set of 18s on her and im chuffed as a chuffed thingy,

when i first got the car the boost was as good as dammit turned right down, sooooo i turned it up a bit and wahey i was impressed,

then i started getting a loud "hom" sound just before i let off the accelerator , and just before the nice pshhhhh sound as its dumped.

then it got worse,
so i turned the boost down again, and now it makes a "hom" sound on heavy acceleration ?

the turbo still sounds lovely when its spinning down, and to be fair it still goes like hot snot with the boost up ,

it dont sound like a vibration sound , if anything it sounds more like a blown seal or summit ?
am i guessing in the dark here .....erm yes yes i am , why cos i aint got experience in this field and as much as i am pretty good at diagnosing problems , they arent problems of the turbo kind ,

any suggestions would be veritably assistive ,

ps : chuffed im now a member of this awesome site ;]

steve

[gti_shaun]

First of all welcome to the site

im sure you are going to get alot of comments like this so i will be first, it is very difficult to say what your noise is unless heard, is the anyway you can get a vid or recording of said noise?

is it when the engine is put under load E.g Going up hill in say 3rd gear just when it starts to boost?

any fault codes?

Is it running standard map or has it been re-mapped?

[running with scissors]

firstly thanks for your interest

the noise seems to kick in at around 3000rpm now , and to be fair if i drive sensibly then you never hear it, but if i dump it, the ominous "hom" sound can be heard , and allthough i suggest it dont sound like a vibration thing,  i spose it could be an out of balance sort of sound.

 will get my digital camera out and blue tac it to the dashboard and see if that can pick up the sound ;]

[topher]

how exactly are you turning the boost up and down? i hope you haven't caused any damage

im going to have trouble diagnosing a "hom" warped flywheel perhaps, or if it's a blowing sound then from the manifold or exhaust maybe?

[gti_shaun]

Im pretty sure i may have the sound you are describing tbh, does it seem like it hits a bit of a flat spot when the sound is on? i feel as if i have to put foot down to pull it through the flat spot and it then makes the sound worse

then again im having a mare with lack of boost and general stuff with my engine at moment.

[running with scissors]

Bingo !!

Gti shaun you are a guru sir ,....

if i go back a few weeks to when it started , thats exactly what would happen ,...for example , cruising on the motorway at 70mph and it would start, for example i could shove the cruise control on and it would sit on the noise ?

so any way, i turned down the little valve thing at the back of the engine, and it stopped the noise, but i lost the ooomph.

not that this bothered me being 40 and all that ( lol )
so anyway, if i squirted it while it was sitting on the noise ( yes i would hit a big flat spot ) and i would be able to get through the noise by just squirting it then backing off ,

it seemed at first as though it started after i pulled my foot off the juice, ....then it started at cruise speed , and now it does it under acceleration , nearly all the time .

unless i drive it like a mondeo , in which case you hardly ever hear it ,

so ...."GTI shaun , wot dya reckon it is , and how much is it gonna cost us m8 lol "

thanks for reading my post , cos two guys suffering are better than one ;]

[Wayne]

Bingo !!

Gti shaun you are a guru sir ,....

if i go back a few weeks to when it started , thats exactly what would happen ,...for example , cruising on the motorway at 70mph and it would start, for example i could shove the cruise control on and it would sit on the noise ?

so any way, i turned down the little valve thing at the back of the engine, and it stopped the noise, but i lost the ooomph.

not that this bothered me being 40 and all that ( lol )
so anyway, if i squirted it while it was sitting on the noise ( yes i would hit a big flat spot ) and i would be able to get through the noise by just squirting it then backing off ,

it seemed at first as though it started after i pulled my foot off the juice, ....then it started at cruise speed , and now it does it under acceleration , nearly all the time .

unless i drive it like a mondeo , in which case you hardly ever hear it ,

so ...."GTI shaun , wot dya reckon it is , and how much is it gonna cost us m8 lol "

thanks for reading my post , cos two guys suffering are better than one ;]

  I cannot help but think tuning down the valve at the back of the engine will not be doing it any good.

[dellenty69]

variable boost controller. cheap £20 thing off ebay? ditch it and go to a specialist and get it properly re mapped!

[Hulmie]

sounds like your hitting a flat spot with Air & Fuel. First thing remove a boost valve if thats what you've been playing with. it wont do the car any good.

Then take the car for a spin and see if your still having the problem.

Also when was the car last serviced? i mean plugs and fuel filter changed?

[richw911]

Bingo !!

Gti shaun you are a guru sir ,....

if i go back a few weeks to when it started , thats exactly what would happen ,...for example , cruising on the motorway at 70mph and it would start, for example i could shove the cruise control on and it would sit on the noise ?

so any way, i turned down the little valve thing at the back of the engine, and it stopped the noise, but i lost the ooomph.

not that this bothered me being 40 and all that ( lol )
so anyway, if i squirted it while it was sitting on the noise ( yes i would hit a big flat spot ) and i would be able to get through the noise by just squirting it then backing off ,

it seemed at first as though it started after i pulled my foot off the juice, ....then it started at cruise speed , and now it does it under acceleration , nearly all the time .

unless i drive it like a mondeo , in which case you hardly ever hear it ,

so ...."GTI shaun , wot dya reckon it is , and how much is it gonna cost us m8 lol "

thanks for reading my post , cos two guys suffering are better than one ;]

  I cannot help but think tuning down the valve at the back of the engine will not be doing it any good.

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