N75F & now limp mode???

[thenofjboy]

I was having boost issues with my KO4 for a while. Pressurized the system once and found the PCV breather hose to be destroyed & i replace that, i haven't done a pressure test since but i will be doing one tonite! I have already checked the plugs, gapping, check places for other obvious leaks, silicone hoses, disconnected the N75 from the WG and boosted like crazy etc...im checkin the DV again tonite, i think it may be in reverse - i hear a slight fluttering sound the other day from that side..
Before i was boosting to only 15psi and sometimes 17 in 4th gear. i got a used N75F and swapped it with my C version, this was was on Monday. Before i was boosting to only 15psi and sometimes 17 in 4th gear. I checked one more time and disconnected the N75 from the WG and it boost like crazy, obviously. So for a couple days my boost was REALLY good, high it was around 20, sometimes even to around 21, had good pull etc. but i did feel like a surge i guess, it happened twice. it has been wet n rainy around me but today it was dry out and was lookin to test it more and rip it on the parkway. I was boosting to around 20 and it was feeling good but later i noticed when i floored it , i wasnt going anywher!! i was hit around 5 maybe 6psi and the rest of the drive home sucked haha. i had no CEL but i checked for codes & got P0102- MAF or VAF a circuit low input. I cleared the codes and waited and still ran the same. O yeh i have a AEB engine, KO4, 1998 etc...
i think im in limp mode. should i disconnect the N75 from the WG again and see how it drives?
TIA :)

[thenofjboy]

maybe the MAF??? I just have to remove it from the airbox and spray that metal strip inside the cylinder, right? im letting the garage warm up as we speak.

[Seerlah]

Use CRC MAF cleaner on the entire inside of the sensor (yeah, I always use a good amount) and reset the ECU.

[cculos]

can someone please solve this? I'm having this EXACT same problem with an ECS n75 race valve. Not sure if it's the valve or not - but surging at high rpm/hesitation and only boosts to 15 psi or so on a k04. Only hit limp mode once, and a few CELs came up when maxing it in 3rd that were reading as misfires on cylinders 2 and 3. Not to thread jack or anything. Would switching out the n75 back to the stocker fix the problem? I may try it tomorrow morning.

[Seerlah]

^ What kind of dv you running? The n75h is supposed to smoothe out surges, not create them. And from threads I have came across, 15 psi is rather weak for the k04-15. That turbo should spike at ~25psi. My little k03s spikes at ~22psi. I would def check for boost leaks.

[thenofjboy]

to reset the ECU, i can just take it out and plug it back in correct? i have a can of CRC MAF cleaner waiting for my to use it :) and the sensor is the rectangle sensor inside the cylinder on the tap portion of the airbox. I have cleaned it before but i want to make sure im cleaning the right thing. there is that oval metal thing on the top of the airbox too, not sure what that ic maybe the ICM...

will a dirty MAF cause limp mode? what else causes it?
TIA

[Seerlah]

I do not know what can cause limp modes. I know overboosting what the ECU is programed for can cause you to go into limp mode. Maybe you hit limp mode because your A/F ratio is waaayy off and the ECU put you in limp mode so that you don't grenade your engine. But I think you can reset the ECU by doing a throttle body adapt (remove the negative cable from the battery for 20 min, hook it back up, place key in starting position for 10-15 min witout cranking. be sure to get the radio code too), not posotive though.

As for where the MAF is located, it is in the air box. The connector for it is under a rubber groument. I actually posted on a thread on removing it. I will post a link. But try the MAF cleaner, then a throttle body adapt for the ECU resetting (I know it can be done via VAG com, just don't know how). Also check for any loose hoses/clamps (the dv usually gets most people) and do a boost leak test.

If you have a VAG com or know anyone close whom does, you should log the MAF in block 003 at 3rd gear WOT. Your g/s should be 160 when throttle is 100% if your MAF is still good. If you post in the regional forum for anyone nearby with a VAG com, there are many freindly people on this site whom are more than willing to assist.

http://www.audizine.com/forum/showthread.php?t=239503 (Scroll down to post #20)

[thenofjboy]

Seerlah- yeh we have talked several times on here but private messaging. thanks again for your help. i looked at your post about the MAF and thats what i thought it was i just wanted someone else to tell me as well.
i dont wanna clean the MAF now but im going to do what u said and remove the negative cable etc..& then ill clean the MAF.
time will tell.............thanks again!

[thenofjboy]

stupid ? but how do you disconnect the MAF? can i do it w/o taken the airbox apart?
i know how to take the MAF out but the wire that connects to it on the inside of the airbox does have a single plug on the top i can disconnect to test it. there are 2 plugs on top that go to that other thing inside the airbox-..thanks

[thenofjboy]

ttt

[Seerlah]

I am going on assumption that your car has an AEB. If that is the case, you will need to take apart the air box to actually remove/replace/clean the MAF. But if you only want to disconnect it, you simply pry up the rubber groument and disconnect the connector from the MAF element. But to check if your MAF is good, you will need to log it via VAG com (with the MAF connected). I would suggest you clean your MAF via CRC, then log it with a VAG com.

[thenofjboy]

update - i took off the hose that connects my new N75F valve to the WG and it boost 15ish but the ground is wet. this is obviously WELL passed my current 5psi i am getting.
I did a pressure test & didn't hear anything - might get some bubbles out ha
tried to re-set my ECU as i talked about before but now i might try literally unplugging the ECU. also cleaned the MAF with the CRC cleaner...sprayed the hell out of it.
is my N75F valve bad already? what gives haha...
im going to connect the hose to the WG - and disconnect the MAF. i do a an AEB but i dont have a VAG. and i just remembered AEB engines dont have limp mode. ill prolly take your advise and look in the regional section for help.

[thenofjboy]

yup so i disconnected the MAF and when i accelerate slowly its ok but obviously im not building and boost. when i floor it or even push it down more it boggs down etc...so no dice i guess the MAF is fine. i connected the MAF again im at 5psi. wonderful ha.
i have read before about a bad O2 sensor or loosing the 3 bolts on the CAT & see how boost is. but i dont think either of these examples because of my huge drop in pressure from spiking 20-21 to 5psi.......

[thenofjboy]

ttt before my cough medicine knocks me outttttttttt ;-)

[cculos]

^ What kind of dv you running? The n75h is supposed to smoothe out surges, not create them. And from threads I have came across, 15 psi is rather weak for the k04-15. That turbo should spike at ~25psi. My little k03s spikes at ~22psi. I would def check for boost leaks.

Not to jack, again, but i'm running a forged bailey's DV from AWE tuning. The k04 software is the base GIAC tune (dont have FMIC or bigger injectors yet). I'll check for boost leaks sometime later in the week - it's so strange though, I KNOW it should be spiking at like 20-25 psi, but it spikes to 15 and 10 is what it's hitting right now :(

[thenofjboy]

Anyone have any ideas why im only boosting to 5psi now and I was spiking to 20psi 3 days ago. I replaced my N75c with a N75F and it was good to go for 3 days but now I cant boost past 5psi. I did a pressure test last night and couldn’t hear anything, ill be doing another one today…..
TIA