Over revving

[Steve. H]

Hello all,
I'm a new member with a 1997 1.9 z3. My problem is.....
When the car is ticking over & revved up it sounds/works correctly. Once driving the car increases in speed.
I'm constantly holding it back on the brakes. If I dip the clutch it revs up to 5k. Once I slow down it goes back to normal again.
Yesterday while driving I switched the ASC off & it cured the problem totally. So...?
Do I need to change the switch or something else?
Steve.

 

[Stevo7682]

Hi and welcome from me in Scotland .
Thats an interesting sounding problem you have sorry but off the top of my head i don't have an answer for that.

 

[DavidM]

Welcome from Ireland! Someone of the experts - I'm sure - will be along with the answer to your query.

 

[Stevo7682]

Right I've had a think about this .
Question does your car have cruise control fitted.

 

[Shelly]

Hi and welcome from me too

 

[Low Rider]

Welcome Steve

 

[GazHyde]

Welcome... I initially thought sticking throttle cable, but not sure why turning the ASC off would cure it.

Gary

 

[Stevo7682]

Gary i was thinking cruise control stuck on as it would only engage in the higher gears hence only a problem when going faster ( Because as you said throttle is cable ) What i wasn't sure of was does cruise disengage if asc turned off . Hence i had asked if cruise control fitted to car or not well at least that's my tuppence worth.

 

[GazHyde]

It's a good call Steve, I'm out of ideas!

 

[Steve. H]

The cruise control is disconnected, as in the stick is fitted to the column but there is no throttle body in the engine.
The air box is fitted straight to the flow meter and then onto the main throttle body. Don't know where the cable has
Been put.

 

[Slam]

Hi welcome

 

[t-tony]

Steve, does this only happen when the car is being driven, (or can you replicate the problem whilst stationary)? If so rule out throttle cable. It sounds as though the idle speed is being held artificially high, most likely as Steve said by a problem with cruise control. Try disconnecting the cruise wiring (at the switch) and see if it has any bearing on the issue.

Tony.

 

[mrscalex]

I've been helping @Steve. H with advice this week and a few bits. In fact I think it's my brownie point for the new member

Are we missing the point? The problem goes away when the ASC is turned off? We know the ASC systems regulates a secondary throttle so I assume that's where the issue is. Or does the cruise control tap into the secondary throttle rather than primary throttle?

 

[Antm72]

Has it been code read does it throw any codes at all ?

 

[mrscalex]

I read the codes. There was an ASC button error. Plus a number of others I suspect were unrelated but I suggested Steve made a note and googled them as I wasn't sure what they were off the top of my head (unhelpful descriptions).

I doubt the ASC button literally means it's the switch that is faulty but I guess it's worth a try. For the sake of a tenner on a secondhand replacement it's a worthwhile first step.

I encouraged Steve to post as this is stretching my knowledge a bit too far and I suggested additional opinions.

I went away to study the secondary throttle system on my brother's 1.9. But it wasn't where I expected it to be as realoem shows it inline in the main air intake trunking near the MAF? No such beast on my brother's car. And studying realoem further suggests there's a second type of ASC - ASC+T? Would my brother's possibly have that? Where does that system live? I don't recall a secondary throttle near the MAF on my 1.9 breaker either.

Is it possible the secondary throttle was removed from Steve's car when the previous owner fitted a K&N air filter? Or is he likely to have the same system as my brother's 1.9 after all?

I noticed 2 throttle cables rather than 1. Is the second one for the cruise control or the secondary/ASC throttle?

 

[Steve. H]

The problem only occurs when in motion, after about 25 mph. Robert I note your point about the secondary cable,
I disconnected that & it didn't make any difference. If it's helpful I could post a picture of the area?

 

[Steve. H]

 

[Steve. H]

 

[mrscalex]

It needs a greater mind than mine to get to the bottom of this. Though I would be surprised if it wasn't one of the things already discussed, i.e. Primary throttle, ASC/secondary throttle or cruise control.

Re: the cruise control wasn't aware your car already had this and had been disconnected. I thought you wanted to add it as a retro-fit installation.

 

[Stevo7682]

The second cable goes to the cruise control motor at the fuse box take it off leave the throttle cable from the pedal on take it back out see iff any different