964 Occasional Stalling Query

[Guest]

Guys/Gals, A problem to be solved!

Whenever I declutch to stop in a queue or at a junction engine revs drop way below idle speed and generally recover up to idle speed in a split second. However occasionally the revs drop so low that the engine stalls, and on restart the revs drop off again and it stalls again. This stalling may heppen 3 three times then after some judicial footwork she idles OK - This seems to happen more on wet days, and after say 5 miles travel i.e. half way to or from work!

Any ideas? The Lambda O2 sensor and the Flywheel sensor have been changed but do not seem to have helped. Is it DME? Would a Bosch Hammer find the problem. The revs only seem to drop when travelling, they dont seem to drop off when you just blip whilst stationary.

Any help would be gratefully appreciated.

Thanks

Terry Webb - 1990 964 C4 (106K)

 

[Dave Wilkinson]

Terry,

It's just a guess but the symptoms you describe sound very much like a sluggish ISV (Idle Stability Valve). The ISV sits in the induction tract and can often get compromised by oil blowback, making it sluggish to move on occasions. The subject has been covered in some depth on Rennlist. Having an overfilled oil tank is one contributory factor but the effects last long after the overfill is resolved.

Cleaning the ISV with brake cleaner seems the preferred method of fixing it.

The good bit is that it's a relatively cheap solution!!!

Regards


Dave

 

[Elliot Davies]

Terry,
also make sure that the throttle idle microswitch is working okay, you will hear it click very quietly if you work the throttle cable from under the engine lid with the engine off. when the throttle cable returns back to the idle position, a little lug hits this idle microswitch and stabilises the revs.
I had this problem after cleaning the engine, dont know why !! it didnt move but a few small hits with a little hammer on the bracket and hey presto never stalled again.
PS. I did take it to Northways up the road and he agreed with me that that was my problem.
Just another possible, I would take a better pic for you but i dont have the car anymore.
[]

 

[Melv]

What fuel are you using?

And when is the last time you took the car for a good thrash?

Pity you are so far away, I'd offer to help.....[]

Mel

 

[964rh]

Mel,

What fuel should be used? i've read so many places saying super unleaded, but was told by 911 virgin when I bought the car that normal unleaded was to be used.

Have always used super in my 16v golf because it runs so much better, but haven't noticed any rough running with the 964.

Thanks

Rob

 

[Elliot Davies]

If its any help, i ran my 964 for 3 years on normal branded unleaded (definately not supermarket fuel) when i went abroad i gave it a treat and used super unleaded.
I also use stp injector cleaner which is supposedly to be used every 3000 miles.
Available cheap at costco []

 

[964rh]

Elliot,

Did you notice any difference when you run it on super?

Rob

 

[Melv]

Yep -ordinary unleaded absolutely fine, but buy a premium brand and NOT supermarket fuel...

My C4 was hot filmed and set up to run on ordinary unleaded. It was actually worse on super!!

Car always goes better for a good thrash if you've just been pootling around.

Debs had the same prob shortly after buying my old C4 -advized decent fuel and a good thrashing!!! []

Mel

 

[964rh]

Mel,

It's the same with Mrs Rob, bottle of Vodka and a good sp......Oops wrong forum
[]

Pardon my ignorance, but what is hot filming??

Rob

 

[Melv]

Hot film, ROb, is the air metering system that the 993 runs, unlike a mechanical flap in the 964.

This, together with revised air intake trumpet and chip put 35brake on top of my 964.

My 964 Cup Car is also fitted with this, and together with revised cams, means a whopping 50 brake over standard That's 285bhp/tonne.......:0 GT3 territory, and how

Mel

 

[964rh]

Mel

Would you consider this to be a suitable for a first modification?

Roughly, how much am I looking at? and who does this?

Not worried about location as I will travel to get a proper job done.

Rob

 

[Melv]

http://www.milfordmicros.co.uk/

Geoff Everett, ex-AmD.

Worth it? Every penny of fifteen hundred quid. I remember my initial reaction when I got back after a test drive -"Geoff, I need new brakes!!" Best accolade was when Nick Faure sidled up to me at Goodwood, he was driving a 993RS -"It's not standard, is it? We had trouble catching you up back there...." []

But if you just want to go faster on track days, the money would be better spent on driver training. []

Mel

 

[Elliot Davies]

ORIGINAL: rob hounslow
Elliot,
Did you notice any difference when you run it on super?
Rob

Cant say i did notice the performance difference Rob, only the price ............. []