engine prob mk4 1.8t

[MidMazar]

I just have a quick question, i've had my gti for about two months, put in a cai. Everything was great until today, basically when i speed up my car boosts then stops relieves pressure and boosts stops and keeps on doing that with the rpms steadly going up. There isn't a constant boost until time for shifting. (off and on off on etc..) It seems like theres something wrong with the diverter valve, but i could be wrong. What are simptoms of a bad diverter valve? Please someone help me!!!!

[boschmann]

It could be, but it also could be vacuum hoses or the little solenoid/valve on the fender well called the N75 valve. You can check all the small vacuum hoses around the turbo & air filter housing yourself but probably will need a VAG scanner to identify the problem otherwise.

[Vin.ZNT]

you mean surging?

what other mods do you have

[MidMazar]

yeh surging, no mods whats so ever just a cai. Seems like the surges stopped, but can't tell what went wrong with it. I checked pretty much all the hoses and nothing. I'm probably going vw look at it and see if all the info is there. I need a boost gauge that would help out a little with analyzing the prob. Hey where exactly id the N75 valve and how do i know when it is shot? Thanks for the responses!!

[Vin.ZNT]

somewhere beside the DV

sounded like it may be your DV's problem, either that or the N75 (since no hoses are loose you said)

but then you have warranty since you don't have a chip, so USE IT! it's there for you to use it, get most outta it, tell VW to fix it~

[Mk2Vr6Turbo]

whi u even go with 1.8T ? they have problems on/off constantly

[edspecR]

all vw's have problems

anyway, it sounds more like a n75 problem than a diverter problem. since you only have a cai, if your diverter was faulty, you'd have complete loss of boost or a slight leak, not violent (relative) on and off periods in the same run. n75 is the solenoid that controls your wastegate and its possible that the solenoid gets/gives faulty messages which makes the wastegate jump the gun or fail to open, etc. the part where you said that it only has constant boost at times of shifting kinda proves it for me, since n75s mainly control the wastegate lag/delay (or lack of) time between shifts (when the wastegate would have to open when upshifting and close when downshifting)

[Vin.ZNT]

if so then get a new N75

try a J, if I remember right, people find it to work smoothly on stock 1.8Ts

also, DON'T order them online, N75s are very fragile parts, there are chances that they'll break before arrival

try and buy them through dealerships