Performance Loss

[T7ODD]

Hi guys. I've owned my Ibiza Cupra for 2 years now with pretty reliable motoring apaty from a couple of coilpacks going. Anyway, my car wasn't performing too well today. It's not remapped and normally boosts at 7psi. Today it has been hitting a wall at 5psi and going no further. Sometimes it may do this but I lift off the accelerator, put my foot back down and get full boost. Today however, it just wouldn't go past 5psi and I took it out a couple of different times. Then the engine management light decided to come on.
I've had a GFB hybrid valve fitted to the car for 4 weeks now. I had the engine management light come on a week after fitting which I reset by disconnecting the battery. After which I no problems with boost and performance seemed no different to when I had the Forge DV on. I have had a bit of a lumpy 'hunting' idle now and then for quite a while too, espceially when air con is on. But it's done this on and off for as long as it's boosted irregularly. The drop in boost has never bothered me before as it would be cleared with a simple dab of the throttle but today it's decided to not boost properly at all. At first I blamed the hot weather for the bad performance but then realised there was something more wrong. I just wonder if it's all linked.
I know some people will blame the DV, well I can try putting the bosch one back on. Some people may say it's the MAF or even a pipe leak somewhere. I can't see how this could happen overnight though.
Has anyone experienced this and could put me in the right direction? Do you think VAG-COM will help and will it tell me whether it's a boost leak or a MAF fault and will I have to do certain logs to determine that?
Thanks in anticipation.

 

[T7ODD]

Just to add, you wouldnt notice any different driving sensibly. Throttle reponse still seems good and turbo kicks in as normal, it just doesn't boost properly.

 

[T7ODD]

UPDATE - OK, this morning I took off the negative battery terminal for 20 mins and changed the GFB hybrid DV back to the OE plastic bosch valve. The car had been sitting overnight and when I started it up it was very lumpy and almost stalled but then was fine, maybe it was adjusting. I took it on two 25 mile runs and it was the same as yesterday, general performance is as normal but full boost is lacking. I did manage to get proper boost twice in 2nd gear which makes me think it isn't a boost leak. about 5 miles before getting back on the second run and minutes after I managed to get proper boost the engine management light came back on again

 

[David_smith_909]

Get it checked using VAGCOM

 

[T7ODD]

UPDATE - still trying to get vag com on the car to read the faults but disconnected the MAF at lunchtime and drove home for lunch. It was not really much different and still boosting the same. I reconnected it and it was no different. I'm unsure whether that points to it being the MAF or not!
However, driving home from work i booted it a couple of times in 2nd and it was boosting properly. Very confused

 

[T7ODD]

Still haven't managed to get hold of VAG-COM but after unplugging the MAF (TCS light also came on) and plugging it back in again after a short trip, the TCS light went off again and the car seemed to be boosting properly.

Vacuum is normal according to my boost gauge so don't think it's any leaks. Still running with my OE DV on the car. I reset the ecu again and the CEL hasn't come on again YET and seems to be boosting OK, although sometimes not as strong as others. I pulled away from a Mk2 Astra GTE up a long hill last night so it an't be all that bad but it did thankfully boost properly at that moment.
Im going to try cleaning the MAF and then do some logs.

For anyone interested, SEAT quoted me £88.24 for a reconed exchange MAF. Part number for the Ibiza Cupra is 06A 906 461 DX. A brand new MAf is around £250 and the part number is without the X on the end.
I was also quoted £34.11 for an N75 valve but was told there are TWO on the engine, can anyone confirm?
If I go down this road then I might look at the 'J' version people have talked about.

I read another topic on here with loss of boost and they had sooty spark plugs and a blocked cat so I may check the spark plugs but the car is running smoothly so doubt it's that.

 

[acidstrato]

never heard of 2 n75 valves on a 1.8T..sounds like a mix up

 

[Forbez]

T7ODD, speak to jblinks, or davidol, re: the maf's, they may be able to sort you out.
(I think Dave works in bosch anyway, but i know jblinks does)

 

[brad_cupra05]

ive been having a similiar problem huting idle underperforming etc like you said seems to pull in some gears not others mine doesnt really pull in first 2nds ok 3rd a bit sluggish im thinking it might be a new maf

 

[leegt5]

It's not remapped and normally boosts at 7psi. Today it has been hitting a wall at 5psi and going no further. Sometimes it may do this but I lift off the accelerator, put my foot back down and get full boost.

I have the same problem but I can hear a vacumn/boost leak somewhere... Just cannot find it !! Hopefully if it goes on a rolling road with the bonet up be able to locate it !!

This hot weather isn't helping, in the middle of the day when its hottest mine will only show 5psi !!

 

[brad_cupra05]

what dump vlave have you got ? i thought changing mine to a forge 007p would solve my problem as my other one was knackered but it doesnt seem to have cured it

 

[leegt5]

what dump vlave have you got ? i thought changing mine to a forge 007p would solve my problem as my other one was knackered but it doesnt seem to have cured it

Originally I had the standard bosch one. but didnt have the money to buy a forge one so bought a brand new bosch one fitted it and its still the same, so either the new one is faulty like the old one or its not the DV !! Having pushed the spring on a Bosch and a aftermarket one the bosch ones seem really weak in comparrison so a Forge one may still solve the problem.. I need to try one out but don't want to buy one and it not solve the problem !!

 

[brad_cupra05]

is there no one around your area who's you could try? but ive just fitted one and hasnt really solved my problem so im not sureif it would solve yours im thinkin a possible n75 valve fault

 

[leegt5]

Are you hearing any sort of leak ? be it boost or vacumn when on boost ?? I was thinkin N75 but would that cause a leakin noise ??

 

[T7ODD]

Under half aceleration you will hear a sort of leaking noise through an induction kit. I did have a vacuum hose leak at one point and trust me, you'd know if you had a proper leak, it's very loud and whooshy under acceleration and you'd probably hear it looking into the engine bay on idle, or get a friend to rev it a bit.
Mine is still dodgy and I'm sure it's either MAF or N75. The engine light went off after 4 days of driving around normally but another 3 days later it's back on again so something isn't right. I now have a seriel ISO VAG-COM lead and a full version of VAG-COM but I'm struggling to get hold of a laptop with a 9 pin serial port on it. I will get there one day

 

[leegt5]

Yeah I can definately hear it when reved, it sounds definitely like its coming from around the DV area but cannot be 100% sure !!

Well if your ever coming up this way and you want to check it on my laptop your more than welcome !! Just give us a PM

 

[brad_cupra05]

i dont think i have a boost leak i recently replaced the standard dump valve with a forge one so its not losing boost there i think i might get a remap to make up for the power loss and is suppose if your running more boost etc the problem might become more obvious?

 

[Radek]

Yeah I can definately hear it when reved, it sounds definitely like its coming from around the DV area but cannot be 100% sure !!

Well if your ever coming up this way and you want to check it on my laptop your more than welcome !! Just give us a PM

I hear the same sound coming from around the DV .
I replaced plastic Bosch with Forge , but leaking/vacum sound is still there !!!
And I also hear presure dump noise like I was having Blow-Off !!!
That's very strange

 

[leegt5]

I hear the same sound coming from around the DV .
I replaced plastic Bosch with Forge , but leaking/vacum sound is still there !!!
And I also hear presure dump noise like I was having Blow-Off !!!
That's very strange

I think the tiny dump noise is normal as my MR2 Turbo had a recirc on it and you could hear a slight dump (Very light and only hearable when driveing next to a wall or hedge).

 

[Radek]

Ok .
But what about this boost/vacum leaking sound ?
One of local tuner said my car pulls hard enough and there is no
boost leak . So WTF is this ?