anybody else experienced this, or would like to test it for me? When cruising sedately around with the air con off, no matter how slowly I back off the car jerks a little. With the air con on, it's noticeably smoother, and is just the usual drivetrain / engine braking business. Idle speed is the same regardless.

This is probably my biggest annoyance with the car at the moment (it's nice having a biggest annoyance this tiny) and if some fiddling with the bac valve or some such could fix it I'd love to...

 

BAC valve is dirty... Take it off and clean it out..

 

Would a dirty BAC valve cause accleration jerkiness too? My '88 stock 13b Vert does this in first and second if you let off the gas then get back on without shifting.

 

TPS is the cause of that problem you have.. It needs adjusted or replaced..

 

cheers glhs. Will give it a clean and see what happens.

 

My 88 vert has always done this. It was much worse after I port & polished the intake. Dosen't annoy me at all though. I just accept it as part of its personality.

 

if it did it with the air con on too I'd forget about it. But it's smoother to drive with air con on, and it'd be nice to have it like that all the time. (but without the lack of power down low from air con obviously)

Anybody know if I'll introduce an air bubble or anything in the coolant if I take the coolant hoses off the bac? I can't get the screws out to avoid it...

 

My '89 S5 has the jerks too. I'm with 13b Power, I have just accepted it as part of the package. I've driven another S5 with the same symptoms. Some cars seem to have it worse than others.

 

ya I think all have some on/off jeckyness. mine does.

the reason it's better with the A/C on is because when you turn it on. the BAC (or the other vavle?) is opening and letting more air in to hold the idle. opening the vavle is basily the same as just pressing the thottle a bit. so in simple terms. when you let off the thottle with the A/C on. it's as if was still open a bit and you never let off all the way.