993: Return to idle not quite right and related(?) stuff

[Mario149]

Morning all, as per the title really. Over the last week or so, I've noticed:

a) when the engine is revving above 2k, if I dip the clutch the revs drop and it over shoots the 700rpm idle by 100rpm or so down to 500/600, then comes back up to just over, say 800, then settles.
b) it does similar when it starts from cold - as it catches it goes up to 1100rpm, then back down a couple of hundred, then back, and finally settles after about 4 or 5 cycles over 10s or so
b) I've also noticed that the car seems to run a bit hesitantly below about 2k rpm, it might do it above but if it is it's slight/I might imagining it/there's more inertia in the engine so it's not as noticeable.
c) fuel consumption seems a tad high, I'm struggling to get more than 22mpg at a 75mph motorway cruise

The car is still completely drivable but since I'm taking it to have a new exhaust fitted tomorrow I'll get them to take a look....anyone got any ideas what it could be in advance? Are they all related?

[LaurasOtherHalf]

Sounds like typical idle stabiliser valve problems & may only need cleaning. It's worth doing yourself as it's so simple, a couple of years ago I did a little "how to" with pictures......
http://www.pistonheads.com/gassing/topic.asp?t=977...

It's worth noting that if yours is a none varioram car the ISV is in a slightly easier place to access.

[Mario149]

LaurasOtherHalf said:

Sounds like typical idle stabiliser valve problems & may only need cleaning. It's worth doing yourself as it's so simple, a couple of years ago I did a little "how to" with pictures......
http://www.pistonheads.com/gassing/topic.asp?t=977...

It's worth noting that if yours is a none varioram car the ISV is in a slightly easier place to access.

Thanks! Now I just have to work out whether I should get them to do it tomorrow (less faff, more money) or wait till I get it home in the evening and do it myself (more faff, less money)

[LaurasOtherHalf]

Mario149 said:

Thanks! Now I just have to work out whether I should get them to do it tomorrow (less faff, more money) or wait till I get it home in the evening and do it myself (more faff, less money)

It really is very simple, you can pick up a litre of white spirits on the way home, put aside half an hour to get the valve off if it's a varioram car (it's a 5 minute job but you know how it is, takes time to find the inspection lamp, get the spanners out etc), less if it isn't, then soak for a couple of hours. Leave it to dry out & whip it back in before you set off tomorrow. At least then you'll know if it was that at fault.

Obviously I doubt the garage will charge you much to do it but if it doesn't solve it you've added to the fault finding bill.

[Mario149]

LaurasOtherHalf said:

It really is very simple, you can pick up a litre of white spirits on the way home, put aside half an hour to get the valve off if it's a varioram car (it's a 5 minute job but you know how it is, takes time to find the inspection lamp, get the spanners out etc), less if it isn't, then soak for a couple of hours. Leave it to dry out & whip it back in before you set off tomorrow. At least then you'll know if it was that at fault.

Obviously I doubt the garage will charge you much to do it but if it doesn't solve it you've added to the fault finding bill.

Hmmm...problem is I have no garage and I won't be home until it's dark tonight Plus I'm setting of to the garage when it's still dark so as to get there when they open at 8 and miss traffic! Dammit, I should have posted this all a few days ago! ....

I think that on principle, I won't let the garage do it tomorrow and I'll do it myself tomorrow night to score some man points

[thegoose]

Mario149 said:

Hmmm...problem is I have no garage and I won't be home until it's dark tonight Plus I'm setting of to the garage when it's still dark so as to get there when they open at 8 and miss traffic! Dammit, I should have posted this all a few days ago! ....

I think that on principle, I won't let the garage do it tomorrow and I'll do it myself tomorrow night to score some man points

In your situation I think I'd definitely be getting the garage to do it - if it's a 5 minute job to remove and can soak whilst they're doing the exhaust then they may not even charge you - certainly if you explain the job and that you were going to do it yourself (so they realise you know how much/little is involved) then they won't try and over-charge you. Man points? Pffft, keep warm and with clean hands.

[LaurasOtherHalf]

thegoose said:

Mario149 said:

Hmmm...problem is I have no garage and I won't be home until it's dark tonight Plus I'm setting of to the garage when it's still dark so as to get there when they open at 8 and miss traffic! Dammit, I should have posted this all a few days ago! ....

I think that on principle, I won't let the garage do it tomorrow and I'll do it myself tomorrow night to score some man points

In your situation I think I'd definitely be getting the garage to do it - if it's a 5 minute job to remove and can soak whilst they're doing the exhaust then they may not even charge you - certainly if you explain the job and that you were going to do it yourself (so they realise you know how much/little is involved) then they won't try and over-charge you. Man points? Pffft, keep warm and with clean hands.

Marcus you big Jessie!

Eith or mario, nowt better than earning some man points in my humble plus if you do it at your leisure you'll get time to soak it properly (for longer I mean) & more importantly dry it out for longer.

[stuttgartmetal]

ISV, or air leak somewhere.

[thegoose]

LaurasOtherHalf said:

Marcus you big Jessie!

For £20-£30 labour it's definitely someone else's job when the weather's this cold, especially when they're the expert.

[chris_w]

stuttgartmetal said:

ISV, or air leak somewhere.

Would this apply to a 996? The above are similar symptoms to my car.

Thanks

[Mario149]

My F355 had an idle control valve so I guess most (older?) cars do

[Mario149]

Person on Rennlist said:

No idle control valve on eGas cars (eGas began in MY1999 C4 and all MY2000 cars).

[chris_w]

Mario149 said:

Person on Rennlist said:

No idle control valve on eGas cars (eGas began in MY1999 C4 and all MY2000 cars).

Interesting, thanks - my car is a '99 C2 so Pre eGas. I'll have a little google...

[LaurasOtherHalf]

chris_w said:

Mario149 said:

Person on Rennlist said:

No idle control valve on eGas cars (eGas began in MY1999 C4 and all MY2000 cars).

Interesting, thanks - my car is a '99 C2 so Pre eGas. I'll have a little google...

If its pre e gas it will have one but it's different to the Bosch ones you find on 3.2s, 964s & 993s.

Iirc it's a smaller size & fitted to the side of the throttle body

[Mario149]

Update so far as I'm sat at the garage:

1) New exhaust fitted, sounds great so far, thumbs up to Carnewal.com
2) Plugging in to computer thingy reveals a shagged O2 sensor which explains why I'm running rich and only getting 22mpg even on a steady motorway run, might also explain the bad idle....they're fitting a new one and we'll see what happens.

Still to do:

Fix roof rattles

So far so good Did I mention the new exhaust is fab?!

[Pickled Piper]

What are the details of the exhaust?

PP

[Mario149]

Pickled Piper said:

What are the details of the exhaust?

PP

http://www.carnewal-europe.com/cpx_p93113.htm

[Wozy68]

Mario149 said:

http://www.carnewal-europe.com/cpx_p93113.htm

You did it then Mario with the boxes Good service from Gert I bet.

[Guybrush]

thegoose said:

LaurasOtherHalf said:

Marcus you big Jessie!

For £20-£30 labour it's definitely someone else's job when the weather's this cold, especially when they're the expert.

Yes, grazed knuckles hurt like hell in this cold.

[Mario149]

Wozy68 said:

You did it then Mario with the boxes Good service from Gert I bet.

Yup, I try not to hang about After 2 weeks of owning the car my gf was like: "I would have thought you'd have put the louder exhaust on by now...." ....bless, she knows me too well