violent jerking and power loss

[Olimat]

Hello guys im new to the forum, and i don't speak english very well...
I bought an audi s2 a few weeks ago, and it has one major problem above a variety of others:
the car violently jerks under load when driving under hard accelerations, i've noticed sometimes it doesn't jerks and it pulls great but its rare, i tried cleaning the maf connector but nothing changed, and i tried to drive with it unplugged and it was even worse, the car has no problems while in neutral and revs freely, when it jerks it feels like it shuts itself down but it doesn't, and then it gives a big kick of power for a brief moment.

im sorry for my english and thanks.

By the way its a 1991 3b s2.

[andyg plym]

Have you done a boost leak test?

[simons2]

Does sound like a boost leak

[5cylinderman]

You most probably have a boost leak. When the ECU detects a difference between requested boost and actual boost it will cut all boost for engine protection and cut all power, which from personal experience is quite an "Oh ****" experience.
My issue was with the O ring on the left hand (port) side of the intercooler which had broken up.
I replaced the O ring with a silicone reducer hose and all was well. This modification has been featured before on this Forum. I can't reference as I'm out and using my phone right now but this modification has been detailed before.
Best of luck!

[Ian Simmonds]

ISTR this known as the Mark H mod.

[Olimat]

thank you guys for responding, the dealer that sold me the car said he had done a boost leak test but it could be a lie, i forgot to say the abs light lights up when shaking, i will proceed to do a boost leak test as soon as possible.

[Rikki Kitto]

If it feels like the car is trying to chuck you through the windscreen it's a boost leak

[Olimat]

yes it feels like it?

[Olimat]

it does feel like it?

[Olimat]

yes it feels like it?

i mean it does, i dont know why there is a question mark

[newsh]

i mean it does, i dont know why there is a question mark

It's a glitch.. On Tapatalk the forum software replaces unknown emojis with a question mark.

[psiconauta911]

Mine did that a few years ago and it wasn´t a boost leak, and cleaning the maf connector didn´t solve it nor replaicing the maf conectors, the cables that went into the MAF conector were broken and had to be changed, solved it and never hapened again.

[Olimat]

Mine did that a few years ago and it wasn´t a boost leak, and cleaning the maf connector didn´t solve it nor replaicing the maf conectors, the cables that went into the MAF conector were broken and had to be changed, solved it and never hapened again.

i tried to unplug the maf, but its worse, you had the abs light when the car was jerking ?
thank you

[Tractor Dave]

A few things can cause boost cut. With my car it was a faulty fuel pump. Do a boost leak check first though as that is the most common cause.

[Olimat]

ok i will try, thank you