Maf again, wtf??

J Eyo

Polo GTI (6) R
guys

mods are: (my copy n paste list)

Pvc delete, n249 delete, 3"TIP, 42DD velocity stack intake, n75h, forge 008, 63mm FMIC, phenolic spacer, 3" DP, 3" mandrel bent SS twin tip exhaust, (4bar fpr, ev14s-sitting on shelf waiting for tune) racing battery, short shifter, 8p knob, powertrack 50/50ad, polly bushed + caster correct, vmaxx xxtreme, h&r arbs, 15mm + 20mm spacers, Osaka 18" racing alloys, drilled discs, rstuff pads.

Problem started about 2 weeks ago, had a leaky boost pipe, thought it may have killed my n75. Now I have brand new pipework, I've tested the n75h out of the car, ran with 008 dv blocked, no leaks, plugs new, coilpacks upgraded, exhaust not leakin one single iota

The N75h new (never thrown me into limp), forge 008dv new, smoke boost tested, tighter than a nuns a.hole all good, maf = brand new bosch unit, old unit was also completely fine.....

Either maf unit unplugged, boosting hard, plugged in, stuttering and missing like anything, new and old genuine mafs...not a single speck of change between either, and, no boost at all

I've haven't a single vcds code under the sun....I'm fresh out of ideas....
 

J Eyo

Polo GTI (6) R
Yah wiring is ok! Green sensor brand new, and thermo. Climate control actual temp reading has me at a steady 99-100ish and dash temp sits steady in 90, all a ok.

Guys I'm actually confused as ****, especially since it was boosting like a champ 2 weeks ago then literally started it up and nada

Running without the maf atm, fuel consumption is actually much better without the maf plugged in....eh?
 

Beeeans

Registered User
I've got the same issue, logged a few runs with VAGCOM and noticed that with the MAF plugged in as soon as I hit 3000rpm it went flat. Logged timing to find this... (Timing in green)

image.jpg


I stripped back my coilpack loom to find it was split here and there, got a new one from TPS today for £38. Fitting it later on after dinner lol.

Not sure what the MAF being plugged/unplugged has to do with anything but I've spoken to a couple of people that have had the same problem, fingers crossed it fixes it!
 

J Eyo

Polo GTI (6) R
both my o2 sensors say they fail the readiness test on VCDS, of course my cat also says the same, but i have no cat....could dead o2 sensors be messing everything up? No spacer on postcat lambda, my installer if I remember correctly said he had it disconnected, but not mapped out....maybe this?
 

Broken Byzan

Photographic Moderator
Staff member
Moderator
VCDS Map User
rear 02 needs to stay plugged in and adaptions will work correctly. What gap have you set the plugs to? Are they std heat range?
 

J Eyo

Polo GTI (6) R
Nkg colder plugs in for 6months, never an issue
 

jamiebennett81

Registered User
When you say new Bosch unit, where did you get this from? From a main dealer or somewhere like Euro Car parts.

Only reason I ask is ECP MAF's are never properly calibrated, and throw up further issues proven by Niki at RTech when mapping cars, they never read correctly. Only buy MAF's from a main dealer.
 

J Eyo

Polo GTI (6) R
Hmmm I'm pretty sure it is a legit bosch all the codes and markings are legit and it cost me $300 from a legit online bosch provider :/

As discovered today even with it unugged my boost is still weak :( after more playing around. Not as weak with the maf plugged in but no where near 100%

Backfiring, very quiet dv, still slightly rough and missing idle.

I'm taking off my charge and turbo boost pipe tomorrow and checking my dp etc, smoke test didn't show anything but I'm doing it anyway for piece of mind
 

J Eyo

Polo GTI (6) R
Last night, with foot to the floor on the freeway already making very little boost, my DV suddenly dropped everything and I got absolutely no boost. Finally got a code, boost pressure limit exceeded, dead n75?

I should note, there have currently been 2 sounds when I release the accelerator, since Ive had this problem. There's the typical whoosh of DV pressure but there is also a metallic cylindrical (if under "strong boost" its sort of a little spit of air" but typically it is a sort of hoot that occurs a split second before the typical DV whoosh. I have never had this occur before and the sound is very weak, as is the typical whooshing DV sound (since I am making very little boost)

Also my gigantic 42DD intake usually sucks in a bucket load of air, and is very, very audible (Literally can be heard from a mile away, however since these issues the sucking sound is also very, very weak and quiet)

I swapped out an n75 from an A4 B6 here, (I didn't reset my ecu) and still had weak boost. Should I try to the swap again, and reset my ecu? Im beginning to think my n75 is wrecked. It was tested out of the car, and seemed to be fine, however it is an n75H ECS race valve, I have heard these are prone to failing?
 

J Eyo

Polo GTI (6) R
so, flipped around my 008 DV, with the MAF connected, it staggers when it hits boost then goes into hard limp and turbo is completely gone. Disconnect maf, hits boost much harder, then again, staggers, big whoosh as the n75 releases everything then heavy limp.....dead actuator??
 

Broken Byzan

Photographic Moderator
Staff member
Moderator
VCDS Map User
When you say new Bosch unit, where did you get this from? From a main dealer or somewhere like Euro Car parts.

Only reason I ask is ECP MAF's are never properly calibrated, and throw up further issues proven by Niki at RTech when mapping cars, they never read correctly. Only buy MAF's from a main dealer.
The ecp/gsf thing is horse radish. No proof I have ever seen and better warranty from ecp than dealers
 

badger5

www.badger5.co.uk
Site Sponsor
When you say new Bosch unit, where did you get this from? From a main dealer or somewhere like Euro Car parts.

Only reason I ask is ECP MAF's are never properly calibrated, and throw up further issues proven by Niki at RTech when mapping cars, they never read correctly. Only buy MAF's from a main dealer.

lol

ECP ones fail more frequently I''ll say that

Bosch maf in in the Bosch box, with the Same bosch EXCHANGE numbers on but TPs sourced ones better than other Bosch sellers?

GSF ones work fine for me an no hassles re warranty unlike TPS. I avoid ECP as they fail too often..
 
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