Strange issue, intermittent loss of power

[rajsta]

Hello folks,

 

Im having a strange issue with random loss of power.

 

firstly i like to mention ive fitted-

new turbocharger,

new Garrett actuator,

braided oil feed pipe+gasket,

oil return pipe+gasket,

new intercooler,

new n75 valve,

new boost pipe seals and clips,

deleted n18 and n239 valves,

new silicone vac lines.

new inlet & exhaust manifold gaskets.

 

Ok so the problem im having is that when i start off driving the car doesn't seem to want to go anywhere,

it will slowly pick up speed and during this time i can hear the turbo spooling, but the car should be going a lot faster compared to how its spooling if you get me, then all of a sudden i will get plumes of grey/black smoke coming out the exhaust. the car feels very bogged down.

 

And then there are times where it will drive as it should,(well sort of), the turbo sounds about right in conjunction with the rpms but i noticed when the turbo comes on full chat it does so too aggressively.

 

also when i start the car i can hear a hissing noise but cant figure out where its coming from! ive checked the servo pipe to the vac pump and it all seems solid.

 

Any advice would be appreciated as i want to get to the bottom of this as the car is perfect apart from this issue.

 

 

 

[Danny 57]

I think you probably realised that the hissing sound is an air leak from some where and just because you have not found it does not mean that it is not there.

Good luck though some one may have a better train of thought.

[jimbof]

does the vacuum go to the brake booster as well?  could it be around there?  I remember reading about brake booster connections becoming damaged.

[rajsta]

I think you probably realised that the hissing sound is an air leak from some where and just because you have not found it does not mean that it is not there.

Good luck though some one may have a better train of thought.

yes ive realised that much.

[rajsta]

does the vacuum go to the brake booster as well?  could it be around there?  I remember reading about brake booster connections becoming damaged.

yes the vacuum does go to the brake booster (ball).  

And the hissing seems like its coming from that side of the engine but i cant be 100% sure due to the noise while the engine is running.

 

Is there any type of test i could carry out to find the source of the air leak?

 

also now you mention the brake booster, (note that i dont drive this car alot) the brakes dont seem very confident, from the top to about a quarter of the way there is no braking effect when i press the pedal.  its not long since i had a full brake system renew which included All Discs,Pads and Calipers, flexy hoses, servo and master cylinder, and fluid.

 

and just to add, this car has never suffered any water ingress as this is the first thing i sorted when i purchased the car years ago.

[jimbof]

Sorry I can't help much more, I just wanted to suggest brake booster as I was aware they have vacuum but you didn't list it.  This is way more complicated than the stuff I mess around with on the car!

 

My (lame?) idea would be that pulling a vacuum or pressurising the system without the car running would make it much easier to tell where a leak was coming from, I guess that could be rigged up?  But really, I'm just inventing stuff now...

[rajsta]

Sorry I can't help much more, I just wanted to suggest brake booster as I was aware they have vacuum but you didn't list it.  This is way more complicated than the stuff I mess around with on the car!

 

My (lame?) idea would be that pulling a vacuum or pressurising the system without the car running would make it much easier to tell where a leak was coming from, I guess that could be rigged up?  But really, I'm just inventing stuff now...

 

Isnt there a service called a smoke test or something along them lines that will show up any leaks?

[rajsta]

im looking for a new brake booster (ball) online but cant seem to even find one,  is it actually called a Brake Booster? or something else?  im also looking for a diagram of the braking system

[jimbof]

Also known as brake servo I believe. Quite a pricey part and a bit of a pain to fit apparently.

[jimbof]

How to here: http://www.ukpassats.co.uk/phpbb/viewtopic.php?t=10572

[rwbaldwin]

It's not unusual for the brake servo to get rusted out by water trapped in the plenum chamber.

[rajsta]

How to here: http://www.ukpassats.co.uk/phpbb/viewtopic.php?t=10572

Thanks jimbof but ive already a new servo and master cylinder fiited.  im talking about the Ball that sits in-between the turbo and engine.  i think it may be called the brake pressure accumulator!

[jimbof]

Ah ok, no idea, sorry!  hope you get sorted.

[rajsta]

Well this is turning out to be a strange issue, ive had the car in at 2 reputable mechanics, both did a vac leak smoke test and found no leaks.

 

even they seem confused as to why the car has got a massive flat spot.!

 

again, its very strange the way this actually happens... i pull off in 1st and try to build up rpm, the rpm builds up, the turbo is spooling but the car is going nowhere and then all of a sudden at around 3k rpm the car takes off like a rocket and chucks alot of black smoke out the back.

 

And then there's other times when i pull of in 1st and build up the rpms and the car produces the power as it should.! it runs absolutely fantastic. 

 

it like a Jekyll and Hyde car at the moment.

 

one of the mechanics said that when he took the car out with whatever it is that he plugged into the car to monitor the engine said that when the car produces the power as it should all the "values" seem ok, but when it goes into this limp mode type way he said the "values" are lower!  im sorry but im not very techy so i didnt really get what he was saying.

 

he also mention if i had the car mapped, which i have about a year ago.  he suggested that you may have had the remap done when the turbo, sensors where all tired and on there way out, and now that youve had the whole boost circuit renewed the remap maybe clashing or something? 

 

is it actually possible for a remap to go out of sync or something when you have new sensors/ turbo fitted? and some sensors removed?