andyd

Hi All,

I’m quite new to 964 ownership, but it’s all going well so far and having loads of fun with it!

One minor problem, the engine’s idle speed oscillates. By the time it’s warm it is barely noticeable but when the engine is cold then it can be quite bad and it makes it difficult to pull away smoothly at the first couple of junctions. I’ve had a quick poke around, disconnected the battery to reset the ECU and cleaned the idle value and it has made no difference. Is this a common fault? I’ve searched the 964 forum, but couldn’t find any references to idle problems accept where a lightweight flywheel had been installed. Any suggestions? It’s not really a serious problem, but it’s a bit embarrassing stalling your shiny Porsche!!

Thanks in advance,

Andrew

John Boggiano

There's a whole shedload of possibilities, but you might try a look at the air-metering flap just beyound the air filter. The contacts on it can get oily/old.

garrett376

Oscillating how much? From the books/posts I've read 880RPM (as an idle speed) with a little variation of +-40 (as noted by John below) is WNL (within normal limits). I think that if it stalls you out just idling, then you've got trouble; but some moving around is normal according to this discussion forum and Adrian's book.

Otherwise my car is broken, too! The engine speed moves around a bit when it's cold, but never stalls on its own. I've stalled it when I first got it, as it's a much heavier clutch than my 65!

John Boggiano

Garrett,

I think you (or maybe I) have misinterpreted something...

IIRC, the idle should be 880 +/- 40 rpm. That is to say, it could be between 840 and 920 rpm, but it should be steady.

Andrew, when you disconnected the battery, did you leave it thus for at least 15 minutes to clear the memory?

Adrian

Dear Andrew,
I would do another DME reset but do it after a nice drive and with the engine warm but in the cold environment. Once you have started after reconnecting the battery let it idle for at least 3 mins and then go for another drive.
If you do a reset and the idle is fluctuating it will record this as normal if you know what I mean.
These things have to be step by step I am afraid.
Idle should be steady and not oscillating unless you touch the accelerator pedal on start then it will oscillate.
The idle microswitch on the throttle quadrant is also worth checking. I have had mine iced up and this causes real problems. As does an iced up idle speed control valve.
Ciao,
Adrian
964C4

andyd

Thanks everyone,

The battery was disconnected for at least 30 minutes while I took the idle valve - so I'm sure the ECU was completely reset... also FWIIW, I'm pretty sure that the ECU will only learn the static settings for the idle valve opening as a function of temperature, so I'm not sure that even if it was adapted "badly" it would cause the idle to oscillate.

I've also checked the throttle shut switch, and that seemed to be okay.

It sounds like the next thing to try is cleaning/testing the air flap - I wanted to do that at the same time as I did the idle valve, but it looked a bit of a pain to get in out... also I was hampered by my little girl who wanted to help daddy

Any other suggestions are welcome!

Many Thanks

Andrew

Michael Delaney

Andy, You might want to check your engine head temperature sensor. If you do a search on this you will find the discussion along with the resistance numbers for the sensor. If you can't find it I will try to find the specs. for you.

GT9111

Check your car's distributor belt.

garrett376

WHoa, I was tired when I made that post... thanks for pointing that error out John!!!! That would be one crazy idle speed!!!!