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J Ozzie
08-02-2010, 06:22 PM
So looking over the boost hoses and such is their anything i should also be looking at that is causing my boost to go haywire?

Symptom: At WOT my boost will go to 15, 10, 15, 10, 15.

Im looking for leaks, and am going to do a Boost test soon. Anything i should cap off or do before i charge the system?


This issue is driving me nuts, it pulls then backs off then pulls then backs off.


Thanks guys. Im gonna pull every boost hose out tomorrow.

hercfe
08-02-2010, 06:29 PM
Sounds to me like the N75 might be cycling

Seerlah
08-02-2010, 06:30 PM
Don't pull all the hoses out, unless you plan on replacing them with silcone ones. Do a boost leak test. Remove the pancake valve from the tip, plug off the port (I found the big metal Sharpies fits in there perfect), unhook the tip from the MAF and pressurise the system from there (I used the DIY on A4mods to make mine). You will hear leaks if there are any.

But your issue does not seem to be a boost leak, but more of a boost fluctuation problem. What dv are you using?

Polski
08-02-2010, 08:13 PM
I had a similar problem, my boost would go 20-15-20-15 up and down...
Gapping the plugs to 0.28 seemed to fix it.

J Ozzie
08-03-2010, 12:48 AM
Forge 007

Im going to check the gap of my plugs tomorrow as well. its just driving me nuts! Mar car goes, then it doesnt, then does and doesnt.... GRRR id like to know what the hell it is.


as for tester its this one right, i was looking at this as well.

Boost Leak Tester (http://www.a4mods.com/index.php?page=webcontent/pages/boostleak.html)

Seerlah
08-03-2010, 01:46 AM
Try servicing your dv. What spring you have? With 15psi, I would either do the green with 2 shims or the yellow one.

nic2000quattro
08-03-2010, 03:50 AM
I had a faulty n75 that caused the same prob (and also overboosting). My money would be on n75 or DV.

turbo kraut
08-03-2010, 07:10 AM
i had a vac hose that was shot going from the intake manifold to the egr causing the same issues

Audi Skate Snow
08-03-2010, 08:13 AM
I would guess N75.

Seerlah
08-03-2010, 12:40 PM
as for tester its this one right, i was looking at this as well.

Boost Leak Tester (http://www.a4mods.com/index.php?page=webcontent/pages/boostleak.html)

I went with that DIY on construction of mine.

Nebone
08-03-2010, 12:55 PM
I had this issue recently. Check the hose that goes from the nipple on the IM above the alternator. It leads to below the IM to the DV solenoid. Mine was blown off there making the DV operate just on the spring pressure.

Polski
08-03-2010, 04:27 PM
as far a leak testing goes, if you are in a hurry just plug the intake hose with a tennis ball and plug ur compressor to that..takes 2 seconds instead of building a pvc one.

J Ozzie
08-05-2010, 03:04 AM
So where do i begin... Lets say yesterday i was up for 24H. Not by choice.

What was to be a tune up day / Painting the valve cover and installing an AEB intake manifold in... Ended in hell!

As my buddie and i were installing the Freshly painted AEB Manifold he pulled up on the metal coolant line that runs across the intake Manifold for some clearnce to install the new manifold and we hear a big SNAP! followed by coolant just spraying everywhere!
as we jumped into the engine bay to look at what the hell just happened we see a nice big crack on the Coolant Flange at the back of the block.. FML

So we ended up pulling everything out......... Again..... filing it down a bit and using good old JB weld (that shit gets hot as you mix it!) to fix the the crack. I also added a hose clamp around the Coolant Flange to keep it tight. So far so good.


We did find a Ripped hose near the back that connects to the Manifold. We replaced it but my boost still dances.

By the time we were done with everything including oil change, plugs, Paint, RE and RE and Re and RE!!!!!! and my tired ass dropping a bolt into the manifold and down into the vlaves it was Light again.. Like it was never dark!
It was Hell! but i now know how to rip an intake manifold and all the coolant lines out in about 5 minutes no joke!

Polski
08-05-2010, 10:23 AM
same happened to me when i was installing my intake manifold.
I reinstalled that metal coolant line about 5-6 times, used up about 2 teflon roles before i got rid of the leak.
It's truly a bitch, there should be a warning for that on the diy..not sure if there is one already.
The worst thing is that its like putting the icing on the cake as the final touch and then the whole thing just falls apart.

mikmot
08-05-2010, 10:44 AM
n...7...5

wildbill
08-05-2010, 03:57 PM
i have changed my n75, boost leak tested, checked all fuel, exhaust, bad connections. diverter valve is set mid spring on the forge 007. im there with you man

J Ozzie
08-06-2010, 01:36 AM
yea dude it was a heart breaker and i was in the USA visiting my buddie. you dont even think about it until it goes. There should be a warning ... DO NOT PULL UP ON THE METAL COOLANT HOSE.

J Ozzie
08-06-2010, 01:38 AM
i have changed my n75, boost leak tested, checked all fuel, exhaust, bad connections. diverter valve is set mid spring on the forge 007. im there with you man

GRRRRRRRRRRRRR This suckssss


PS. anyone know how to replace the oil dipstick thing. my buddie broke it off so its taped on

wildbill
08-06-2010, 08:08 AM
check the vacuum line from the n75 to the wastegate actuator, seemed to help mine....but the issue is the ecu learning, car is still being painted so no long term results

J Ozzie
08-06-2010, 02:03 PM
will do thanks.

Robb12
08-08-2010, 05:19 PM
Soooo sorry to revive this from a couple of days. I just put in a k04, HFC, APR TIP, & ecu. I got a new N75 about a year ago, I'm using the 710N DV, AND I checked for boost leaks (found nothing). My fluctuating boost didn't occur until my k04 swap. Any idea what could be causing this?

J Ozzie
08-08-2010, 10:19 PM
id like to know too..... Stupid ass boost!

walky_talky20
08-08-2010, 11:11 PM
First thing to do is log actual vs. requested boost on a 3rd gear pull. Vag-com measuring block 115. Log your MAF while your at it, and take a look at your long term fuel trims. Report back with the results.

Are either of you guys still running with an N249? If so, bypass that and see if it helps.

Robb12
08-09-2010, 12:47 PM
I actually just pulled a code for a misfire in cylinder 4, that just recently popped up and my boost stopped bouncing from 10-15-10-15 psi. Might just be the N75 cycling and it's settled. I'm gonna switch out coil packs tomorrow to see if this does it for me. Otherwise I'll run logs.

J Ozzie
08-10-2010, 02:34 AM
I know when i logged last time, it kept saying Overboost

Robb12
08-10-2010, 01:41 PM
I'm actually curious at this point..could a coilpack even cause this issue or no? I'm taking my car to get diagnosed by VAG-COM tomorrow morning and I'm getting worried that a couple of coilpacks wont fix the issue..

nic2000quattro
08-10-2010, 02:52 PM
overboost... well, check your N75! if you can blow thru all 3 prongs it's stuffed... it's causing a boost leak, and will lead to overboost. I had a brand new n75j from ECS that had a leak in a valve caused lots of boost problems and overboosted whenever loaded so bad it would detonate

wildbill
08-11-2010, 07:51 AM
overboost it is, at least for me....after changing the two vaccum lines off the n75, it leveled out in about 15 min of driving....why? at low pressure those lines held, which is probably why you were ok until the k04, and the dry rot of 10 plus years just becomes evident under higher pressures, 2 dollar attempt....try it the overboost is because after the n75 the pressure to open the wastegate was bypassing through the cracks, not opening to specification and then causing overboost

ECS Tuning-Audi
08-11-2010, 01:47 PM
overboost it is, at least for me....after changing the two vaccum lines off the n75, it leveled out in about 15 min of driving....why? at low pressure those lines held, which is probably why you were ok until the k04, and the dry rot of 10 plus years just becomes evident under higher pressures, 2 dollar attempt....try it the overboost is because after the n75 the pressure to open the wastegate was bypassing through the cracks, not opening to specification and then causing overboost

Agreed, this would be a good place to check first. A failed N75 typically underboosts.

wildbill
08-11-2010, 08:00 PM
<<<likes being right way too much

nic2000quattro
08-11-2010, 09:31 PM
the long prong on my brand new N75 was faulty (i think it was the tip outlet but im not 100% anymore) (ecs replaced it for me no probs) andf would let air thru if you blew thgru it (shouldn't be able too).. let to serious overboost and detonation. no damage done to the car thank god... but n75 is a tricky fella is my point

wildbill
08-12-2010, 04:35 AM
thats a rarity, more often than not its something else...people are always ready to yell dv, n75...and the ones that do....those are the only two parts they know

J Ozzie
08-12-2010, 02:36 PM
So, the other night was fun..

Think i may have fixed some issues..

My buddie didnt tighten down all my Intake Manifold bolts. ( Tightened)

So i go out for a drive and bam boost is back but hitting 22Psi..
Again i put my foot down to build boost around a bend which leads to a big hill.... and then i hear a big PSHHHHHHHHHHHHHHHHHH and car dies. FML Leaving me with a stalled engine, no brakes, no power stearing and a turn coming up at the end of the hill.
So here i am Jamming the brakes as they get harder and harder turning the steering wheel as best as i could. I make it around the corner and coast to a spot on the road out of the way.

Having the PSHHHHHH sound i know right away its a boost leak of somekind, and a bad one too because the engine wont run now and if it does it has harsh idle and smells hella rich!

its about 1:30 am and im looking all over.. had no tools noting. So BCAA it was and a tow came and towed me home.


Wake up the next day, Now i can see.. I pop the hood and what was it...... It was the Sensor that attaches to the Intake Manifold that we forgot to screw in last time, I guess building that much boost shot it out..


Car seems good for now, but im still building crazy boost.

Robb12
08-12-2010, 03:04 PM
Got my car logged at a shop and they concluded my problem is a leak so I'm going to do my third boost leak test of the week. But as for your problem, maybe you could hook up a mbc to prevent the boost build up. It seems nic2000quattro solved the overboost problem with the faulty N75, have you tried checking that yet? Is the boost still jumping around?

nic2000quattro
08-12-2010, 06:40 PM
guys im not telling him his n75 is def the prob, just that it does happen. yes lots of ppl go on about these two valves... but it's warranted because they do often fail - even brand new! Often n75 just gives wierd boost issues, but it can also lead to overboost as it did in my situation.. that was all I wanted to contribute. i was working 6.5 days a week last few months and could'nt get the time to do work myself on the car so my car lay at 2 mechanics for weeks on end with me telling them to replace the n75 (they refused to believe it was the prob as it was new). they were vagging it. they got the shits and leftbthe prob with me which i fixed in 10 mins after checking the valves on the bugger. its very easy to check. Never tried it, but a smoke boost test might help

walky_talky20
08-12-2010, 06:48 PM
I've seen a faulty N75 cause overboost on my buddies Stage 3 S4. Had 85k miles and it was useless at controlling 2 K04's at the higher boost requests. Overboosted enough to invoke fuel cut. He replaced it and the boost was back under control. I kept the old one in my toolbox as a possible "upgrade" for my A4 ;) . It acted sort or like "Super" Race N75, lol.

It seemed to me that the internal spring that worked against the solenoid was getting tired. As such, less input duty cycle was required for a given boost level. The solenoid works to cut off boost pressure from getting to the wastegate actuator. In this case, when it tried to cut it off a little bit (small duty cycle input), the solenoid overreacted (or it's opposing spring was too weak) and it cut off more pressure than was requested. Bingo, OVERBOOST.

J Ozzie
08-13-2010, 06:38 PM
yeah but if its faulty, wouldnt you get a code, or would it not make a click when you plug it in?

Maybe i should just bypass it and go MBC

nic2000quattro
08-14-2010, 01:47 AM
the original n75 i replaced it with did give a code. The faulty n75j didnt, as it was basically a leak in the system. So it wasn't picked up on diagnostics

J Ozzie
08-17-2010, 05:18 PM
anyone here bypassin the N75 with a MBC?

Dynamite
08-17-2010, 06:01 PM
I have the same issue. And I have bypassed the N75 with a MBC before, it works alright it just means that you dont get partial boost, if you want to accelerate a bit its not really an option. The way I use now is in parallel. plum in a T on each side of the N75 and then set the MBC to the max boost you want, means you still get partial throttle and you dont over boost.

J Ozzie
08-18-2010, 02:30 AM
Humm, i might just try that.