boost loss / hesitation when accelerating

[mister_bob]

new to the forum fellas, Bought a 2002 180 Cupra a couple of weeks ago that has had stage 2 tuning mods and is running around 230bhp/250 ft-lb - thing is, when I first bought it, it felt really strong through every gear, pulled really hard even in 6th and was really smooth.
Over the last week or so ive noticed that it feels like it "stutters" slightly when accelrating lightly and im pretty sure I can hear the DV quickly opening/closing releasing boost while still accelerating. It also doesnt feel as though it pulls as hard as it used to.
The car has just had a full Seat service recently so should rule out the usual plugs,oil problems etc.
All the mods have been proffesionally fitted as the car used to belong to "Performance Tuner" magazine which showed the various work being carried out so Im happy its not because of bad fitments,crap hoses etc.
Any help would be appreciated cheers!

 

[LEE69]

What boost is it running?

 

[mister_bob]

Im not sure yet mate, I have a boost gauge on order.

 

[LEE69]

How did i know they never fitted a boost gauge, it's the first mod imho you should do, you really need to know what boost and vacuum it is drawing to help diagnose problems.

 

[mister_bob]

yeah, I would have thought so too, ill let you know whats happening when I get it fitted.
Out of curiosity, would the N249 bypass mod help it as Im about to start doing this when i receive the vacuun hose?

 

[LEE69]

It will stop it dumping on part throttle.

 

[Pyro]

Welcome to Scn mate

Have a little read of this it will give you an idea of some of the many things to check
http://www.seatcupra.net/forums/showthread.php?t=293436&highlight=suffering

 

[Phoenix27]

It will stop it dumping on part throttle.

Is that REALLY what the N249 mod does? (i've done it but never knew why, is that bad? LOL!)

By 'dumping on part throttle' you mean automatically... (I.e. full boost as long as your foot is down on the peddal?)

 

[mister_bob]

Ok, heres the latest update.
Ive got my boost gauge fitted and heres whats happening:

At tickover, the vacuum is reading -30 to -32 vac.
At full throttle (in 3rd gear onwards, Im getting a max peak boost of about 18 PSI which then tails off to around 12 PSI. It pulls strongly at full throttle.
Im still having trouble with the "hesitation" at part throttle and have noticed a few times that if i only give it half throttle, the boost gauge fluctuates and I can hear the DV releasing boost.
Ive since checked my plugs and coil packs for discolouration/excessive carbon but they seem fine.
Ive also checked the hoses from thre DV and the air intake but cant find much wrong.
Ive stripped the 007p DV valve and it seems fine

This is starting to get on my nerves now as it ran sweet a few weeks ago.
Helpful ideas much appreciated!!!

 

[Pyro]

Think you may have a vac leak mate you vac should read between -20 & -22

 

[mister_bob]

Think you may have a vac leak mate you vac should read between -20 & -22

which pipes should I be checking for a vac leak mate?
are they the ones located under the inlet manifold?

 

[Pyro]

Think it will be them mate bot to sure where the vac pipes are Lee will know this

 

[LEE69]

Is that REALLY what the N249 mod does? (i've done it but never knew why, is that bad? LOL!)

By 'dumping on part throttle' you mean automatically... (I.e. full boost as long as your foot is down on the peddal?)

Yes does it itself, silly car, can't do it when bypassed.

which pipes should I be checking for a vac leak mate?
are they the ones located under the inlet manifold?

Any of the pipes under the manifold, basically anything connected to the breathing system, if it leaks you get a boost leak, hence limp mode.

 

[Topsie]

-30 vac? Surely thats on the other end if the scale, that's a really good vacuum! Mines wobbling around 14-18 vac, and I think I know the hesitation your talking about, but mine only seems to do it when it's cold, the feels like it's holding back an you can hear the boost dumping, then it closes the n valve and it runs normal again...

 

[LEE69]

14-18 is about right, from memory, when the car is cold when it has warmed up 20+ is considered ok.

 

[Cowie]

Ok, heres the latest update.
Ive got my boost gauge fitted and heres whats happening:

At tickover, the vacuum is reading -30 to -32 vac.
At full throttle (in 3rd gear onwards, Im getting a max peak boost of about 18 PSI which then tails off to around 12 PSI. It pulls strongly at full throttle.
Im still having trouble with the "hesitation" at part throttle and have noticed a few times that if i only give it half throttle, the boost gauge fluctuates and I can hear the DV releasing boost.
Ive since checked my plugs and coil packs for discolouration/excessive carbon but they seem fine.
Ive also checked the hoses from thre DV and the air intake but cant find much wrong.
Ive stripped the 007p DV valve and it seems fine

This is starting to get on my nerves now as it ran sweet a few weeks ago.
Helpful ideas much appreciated!!!

Pretty much the same as mine regarding boost, except on tickover mine sits at -22 all day long, but I too have the "hesitation" that you talk about,have done a throttle body clean and reset with vag-com, is slightly better but heading down to will at P-torque soon to get it stage 2 and see if that smooths everything out.

 

[mister_bob]

-30 vac? Surely thats on the other end if the scale, that's a really good vacuum! Mines wobbling around 14-18 vac, and I think I know the hesitation your talking about, but mine only seems to do it when it's cold, the feels like it's holding back an you can hear the boost dumping, then it closes the n valve and it runs normal again...

yeah, exactly.
Feels like a misfire when at low acceleration so you stick your foot down and all hell breaks loose!
Really annoying cos youre either bumbling around or sliding around bends at full boost lol!

Im gonna check the vac pipes this weekend and hopefully have an update to let you know what I find