MK4 GTI 1.8T ARZ power issue

[james1981]

Hi im new to vw's so not very clued up on them yet. and thanks for any help in advance. right the problem is i seem to lack power and or boost(ive checked all boost pipes all fine), i have ordered a cheap dtc reader off ebay to see what that brings up. First of all i would like to know what the housing is on the end of the secondary air pump pipe, if i follow the plastic pipe from air-filter down to SAU and then follow the other plastic pipe back up to engine it leads to a brass looking housing(is this a EGR). Also the car has been decatted but there is a primary lambda sensor or pre cat lambda would this cause problems in the power of the car and if it does what is the solution without putting a cat back on thanks. Once again thanks for the help.

[rio_gti]

firstly welcome!!

so how do you know you have lost power? was it quicker than it is now or has it always been slow? because i hate to break it to you but these 'turbos' arent quick till they have been mapped!!!

get ready for empty pockets 

[james1981]

well for starters the thing seems to struggle even to get to 100mph never mind the age it takes to get to 120mph. i can here the turbo boosting up little loud if you ask me (a whooshing not whistling lol). tried to replace n75 with used part still no change. sometimes in little glitches its like the turbo kicks in and slams me back then most times just feels sluggish but i can still here the turbo. i have owned fords most of my life, my last car was a 2006 mondeo tdci 115bhp and the golf does not feel much more powerfull than the mondeo. i have cleaned the TB. it seems to struggle at higher revs in 3rd 4th and 5th like theres nothing there and slowly picks up. the turbo seems fine. checked all inter-cooler pipes and they are fine, not checked the breather hoses yet under manifold etc, even replaced the brake switch in-case it was that.

[james1981]

forgot to ask as-well, is that if i take the inlet manifold off to have a good look at pipes etc under there i wont have to mess setting the Throttle Body again with the vcds.

[rio_gti]

hope those speeds are on the race track....

if its whooshing sounds like the dump valve is opening befor it should so id check that first to see if it has split (take it off, suck on nipple and put tounge on nipple once vacuum is there and your tounge should stick to it, if it doesnt stay stuck on the nipple it is shot) so uprate to a forge 007/8 p

also you could do a n249 bypass this may also help premature dumping 

apparently once connected back up again you can turn ket to ignition on and it will align itself but i always use vagcom

[Granta Gti]

Mass air flow sensor? Try unplugging it and taking it for a drive or borrow some1 else's if you can.

[james1981]

it was not on public roads i did the test lol. i just would not get away with it, i have bad luck.

heres the dtc codes that came up today.

16486 Mass or Volume Air Flow Circ Low Input

17580 Throttle Actuation Potentiometer Sign.2 Signal too Low

17947 Clutch Vacuum Vent Valve Switch Incorrect signal

17952 Throttle Actuation Potentiometer Signal too High

17956 Boost Pressure Contr.Valve Open

17987 Idle Speed Contr.Throttle Pos. Adaptation not started 

although i did switch the pipes around on the n75 valve so the 17956 could have been me. Let me know what i need to do thanks guys.

[rio_gti]

 16486/P0102/000258 - Mass Air Flow Sensor (MAF/G70): Signal too Low
Possible Symptoms

    Malfunction Indicator Light (MIL) ON
    Loss of Power

Possible Causes

    Wiring and/or Connector(s) from/to Mass Air Flow Sensor (MAF/G70) faulty
    Mass Air Flow Sensor (MAF/G70) faulty

Possible Solutions

    Check Wiring and/or Connector(s) from/to Mass Air Flow Sensor (MAF/G70)
    Check/Replace Mass Air Flow Sensor (MAF/G70)

Special Notes

    In MY 1995-2002 (?) in Europe at VW-diesel-cars G70 had the bad reputation of slowly losing his performance, causing loss of power. It's not a matter of defective or breaking down, but it is filthy / dirty (not easy to clean). You can check functionality by making a log in [01-engine], [meas.blocks-08], group 003 (3e gear, full throttle, from 1700-4000rpm)

17580 Throttle Actuation Potentiometer Sign.2 Signal too Low
17947

couldnt find


17956/P1548/005448 - Boost Pressure Controle Valve (N75): Open Circuit
Possible Symptoms

    Irregular behaviour
    Loss of power
    Limp mode

Possible Causes

    Wiring and/or connections faulty (short circuit)
    N75 faulty

Possible Solutions

    Check wiring and connections
    Check / Replace N75

 17987/P1579/005497 - Throttle Actuator (J338): Adaptation Not Started
Possible Symptoms

    Malfunction Indicator Light (MIL) active

Possible Causes

    Throttle Body Alignment (TBA) not performed

Possible Solutions

    Perform Throttle Body Alignment (TBA)


hope this helps... got it all from http://wiki.ross-tech.com/wiki/index.php/Main_Page

[james1981]

Looks like i will be ordering a new MAF, i have had no limp mode or MIL light on though. how much would it cost to get the TB done, cant be bothered with doing it myself and paying the £40 i think it is to register the software. also what about the clutch switch thing any ideas.

[rio_gti]

check the wiring first as a mate of mine thought his audi was slow till i saw the wire had come out the n75 valve, he loved it one it was plugged back in