DP cat delete, o2 sensors

J Eyo

Polo GTI (6) R
I have had my 3"dp installed for a long time now, however, i get both o2 sensors fail when i do the readiness test (and of course cat fail) will this effect how she runs?

I put on a FMIC about 4months ago with bodgy pipework, when the pipes were holding she boosted nice and hard (most of the time...) since putting in an aluminium setup, definitely air tight, its running bad at idle, limp mode is always in effect, ideas guys?

New maf, new dv, new n75, catch can, inlet mani is sealed tight, all hoses are new and sealed, so, bad actuator?
 

J Eyo

Polo GTI (6) R
smoke pressure test done, n75 tested out of car, dv tested out of car and actuator tested, all 100% ok, still, no boost....bad 02 sensors?
 

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?
 

S3 Hilife

It's an addiction
VCDS Map User
Gold Supporter
Do you mean disconnected electrically or they fitted a blanking plug and left it connected electrically? I think I would fit a spacer on the post cat O2 sensor and reconnect it or code it out altogether and also make sure that they haven't disconnected the pre cat sensor aswell as iirc this will affect fuelling and upset the ecu.

Steve
 

J Eyo

Polo GTI (6) R
Ok checked and everything is plugged in, I've got no cat; would not having a spacer on the rear O2 cause issues? It's been like this for almost 6months and I lost boost about 3 weeks ago I can't see this causing a problem out of the blue? Still, both sensors and cat (of course) fail readiness test
 

jamiebennett81

Registered User
Have you not answered your own question, that when you switched to an aluminium setup you started having issues?

Has the cat been mapped out also?
 

J Eyo

Polo GTI (6) R
Hey mate, sorry no, this issue started first which made me change out to aluminium piping thinking it would solve it.

Smoke test revealed not a single leak, anywhere and Ive been catless for half a year and no issues here thus far.

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 with my gigantic intake usually sucks in a bucket load of air, and is very, very audible (Literally audible 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?
 

jamiebennett81

Registered User
Have you checked your DV?

What happens if you unplug your N75 and just run off actuator pressure?
 

J Eyo

Polo GTI (6) R
brand spanking new 008 forge unit, if i unplug the n75 it feels the same as if its plugged in atm :S
 

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??
 
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