Over boost?

[jamie9048]

Right first drive of my S2 in three years and its all going great loads of power smooth, car feels really good, memories flooding back blar blar blar...

after 10 miles of fastish driving stopped to talk to my mate on the way home 10min later resumed my journey

I got onto a nice wide A road and went to pass a car pulling well in forth when all of a sudden the car starts pulsing under load. similar to a miss fire. off the throttle the car goes back to normal.

so the road clears and again I go to speed up on boost only for the same to happen again I tried pushing through but it stutters all the way throught the rev range it only stops when I drive the car with small throttle openings

does this sound like over boost?

the car has a turbosmart bov

it is apparently chipped to 270bhp

all done by previous owners

It did this before the car was laid up and I must have forgotten about this but its all come crashing back

[rj scotty]

It's boost cut, very violent. Almost always caused by a boost leak. Even the tinniest of leaks can cause this. You will now have a fault code stored in the ecu. Very common.

Check all hoses, especially the very thin ones at the back of the manifold.

[rynaqui]

Check the plugs and coil packs as well as checking pipes for tears and a boost leak test.

[rxl]

had similar stuff with n75.. changed and drives like hell

[jamie9048]

Just changed the plugs and upgraded to pencil coils where does the N75 valve live? I think its an electrical comp breaking down as the car drives well for a period of time then goes off

thanks for the replies Its nice to know others have had similar problems and fixed the faults think I`ll look at the N75 valve next is there any way to test before replacing ?

[UrS4boy]

...when all of a sudden the car starts pulsing under load. similar to a miss fire. off the throttle the car goes back to normal....but it stutters all the way throught the rev range it only stops when I drive the car with small throttle openings.

I think you have an unresolved ignition problem or a boost leak.

[rxl]

Just changed the plugs and upgraded to pencil coils where does the N75 valve live? I think its an electrical comp breaking down as the car drives well for a period of time then goes off

thanks for the replies Its nice to know others have had similar problems and fixed the faults think I`ll look at the N75 valve next is there any way to test before replacing ?

fowlow the hose from the wastgate and you will find it..

[Cottis]

[QUOTE=jamie9048;752731]Just changed the plugs and upgraded to pencil coils where does the N75 valve live? I think its an electrical comp breaking down as the car drives well for a period of time then goes off

Try unplugging the MAF connector and plugging back in. Might not be that but it is so quick and easy to do and is what was making mine cut boost around 4000rpm. Instantly cured my problem last year. If it has been stood while, the contacts might have got grumpy (might)

[UrS4boy]

...where does the N75 valve live? I`ll look at the N75 valve next is there any way to test before replacing ?

Go to the Engine Bay Device Map below and click on the N75 label in the lower left corner of the diagram. It and all the other labels are live links to more info.

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[psiconauta911]

The cause in mine, for the same peoblem, was dirty eletrical conections, the MAF and the TPS, after changing the n75, the plugs, searching for boost leaks(none), and doing the MarkH. mode it all came down to wigling the maf conector from time to time and cleaning them with contact cleaner, had this problem for years, it came and went, after disconecting the MAF, finaly it got worst and began afeccting the tick over.............in the end just dirty electrical conections due to age and long time standing! Hope it helps, begin with this because is the simpler maintenance, no pricey parts to change!

[newsh]

Yep my first thing to try would be the Maf connector, unplug - replug it a few times and drive, see if it makes a difference.

I chased this problem for years, see my thread on the subject. http://www.s2forum.com/forum/showthr...=maf+connector

[jamie9048]

Tempted to go to the garage now lol got a few pointers thanks for the help

I`ll try the maf and n75 tomorrow

cheers

[Rikki Kitto]

Mine does this as and when it feels like it usually just as I'm trying to overtake somat. N75 was plumbed in wrong at one point, maf connectors needed cleaning replaced all boost hoses and small vacuum lines but still throws a strop now n thenGood luck keep us all posted

[Rusty]

Over boost is violent and throws you forward in the seatbelt; if it's a bit softer then its could be a spark issue.

[UrS4boy]

Over boost is violent and throws you forward in the seatbelt; if it's a bit softer then its could be a spark issue.

I think you have an unresolved ignition problem or a boost leak.

BTDT with a dieing OE coil and then later with one of the first 115L 1.8T coil packs I used started to die at WOT/Full boost.