Hi. I just bought a 1990 C4. My last (years ago) Porsche was an 84 Carrera.
My question: The PPI results were good. Recomended major servicing and some other parts, and the tech said my clutch felt like it may not have too much more life in it. I drove the car for a week; the clutch felt fine to me.
I just got it back from the shop, having done the major servicing. The engine is quiter and smoother, its a repitable shop, but now I'm having a harder time taking off from a stop in that I feel like I'm going to stall (did 3 times already, didnt before servicing). It just feels like I can't get the clutch / gas timing and end up giving it too much gas to compensate. The idle is now lower (probably to speck) but I feel if it was a little higher I'd have smoother starts: make sense? Is there a simple idle adjustment screw I can tweak? The shop is 1 1/2 hours away so I'd rather do it myself. Thanks.

PS- Is it possible that my last 84 handles tighter (less tire chirp) in the corners then my 90 C4, is my memory just fading? Thanks

 

There is no idle adjustment on 964's. It's handled electronically. Do a search on ISV (Idle Stabilization Valve) Cleaning it, can sometimes help the idle speed. You didn't say what your idle speed is. Spec is 880
RPM +/- 40.

 

hmmm... different creatures, for sure.
(I owned an '85 before the 964.)
And I don't recall tire chirping differences between the two.
A factor purely of tire differences, perhaps?

I do know I can do things with my 964 (around the edge of adhesion) that I never, never tried (very often) in that ol' '85.
I love the 964's 'dancing' talents through the corner at the edge. The 3.2's, not so much.

Oh - and welcome!

 

Check your throttle at the throttle-body. Be sure that the idle switch gets contact... it can be mis-adjusted. With the car off, gently open the throttle, and you should hear it click open/shut. Same goes for WOT switch.

Does your car have the LWF or a non-stock chip setup? These can both add to a driveability issue. (taking off from a light etc). Also recent posts here have covered a dirty/clogged intake causing these symptoms.

 

Thanks. what would be the syptoms of the clutch giving out? Anything like I described in my thread?

 

Not in my experience. A worn clutch can slip, chatter etc. And the pedal effort is higher than with a new one. I had issues with my car until I understood the LightWeight Flywheel, and the touchy throttle. Even now after 3 years of daily driving, I will periodically f-up and slip or stall. It happens.

 

I have4 a 1990 C4 as well. If the idle is also erratic then you need to have an adaptation performed with a Bosh Hammer to set it correctly (nothing else works). This is a result of having the battery disconnected and you will have this problem every time the battery is disconnected. The later 964s do not have this problem. Hope this helps.

 

I have a 1990 C4 and never experience any idle problems after disconnecting the battery. I just go for a spirited drive, using all the gears. Sometimes referred to as a" DME reset".

 

Wow! You are lucky, it has never worked for me and I've had it reset many times by my local shop. Maybe they changed something after a certain build date because I know other 964s have had the same problem. Good to know. BTW- my car was built in March of 1990.

 

Is it possibly a timing issue? The clutch on these cars don't engage until you release the pedal about an inch from the fully depressed position. If you're new to these cars, they're really easy to stall ... C4 even more so.

You don't really apply the throttle until you begin to release the clutch pedal--in tandem. I know it feels like you might be burning out the clutch but that's just the way they work.

 

Thanks for the responses. It's been much better the last couple days - I'm sure it was just a matter of getting used to it (and perhaps no longer wearing high heels ;-). It does still feel like it's going to die for a second when I come to a stop with that low idle, which dips lower for moment, but it hasnt died yet. Just a case of getting aquainted with a new car.

 

A further point ot consider - when mine behaved like that it was down to a tired air-metering flap.

 

I have the LFW and RS clutch assembly on my 90's 964 and as I am used to a sequential gearbox
on my other daily car, it is sometimes a pain in the a**....
its too delicate, but if you use the car every day you get used to it (I reckon)

 

One last thought from me, too. I've noticed that the 964 is somewhat sensitive to fuel brands. In my case, (here, in the Chicago area) early morning stalls were rare after filling up with BP gasoline instead of Shell or Mobil. 93 octane, always.

Since there's plenty of variation in fuel mixtures across geographic regions, I'd suggest you try different gas stations in your area to see if one delivers better performance than the others.

$0.02

 

Fog City -
- Check your ISV/ Idle speed control valve - it may need to be cleaned - is the idle stable or erratic ( moves up or down a couple hundred RPM -
On the back side of the ISV there is a small rubber plug ( is most cases it is gone) at the top - but you can not see it from the rear of the engine because it is on the other side - In this small hole is a allen head screw that controls the size of the opening in the ISV valve screwing it out opens the size of the ISV opening screwing it in closes the opening - this is affect controls the idle. If the ISV valve is worn or dirty this adjustment may not work, I have seen some cases were the screw will get stuck and can't be moved. I think it is a 2mm allen wrench.
Try screwing this out a little and see if your idle speeds up -