Idling on cold 911 '89

[imported_Trev Jaso]

Hello all,

I've recently purchased a stunning 911 '89 targa. last of the 'k' series.

the only problem i have is when cold starting, the engine labours, up, down between 600 - 1200rpm. after 10 seconds it levels to 1000rpm. For the first ten minutes of driving (until warm) it will intermitently stall at junctions. The revs will drop, and not catch, thus stalling, when warm, engine idle stabilises

I've checked the throttle position switch, idle position switch, speed sensor, the volume airflow sensor and intake air temperature sensor, cylinder head temperature sensor, altitude correction switch and have been in the process of checking the idle speed control valve. All shows correct electrical resistance and harnesses show the correct volts.

I am unsure about the idle speed control valve as when you turn the ignition, there is a humming sound, but it pulsates, and looking into the valve, the rotor inside pulsates slightly. Is this correct, or does it need replacing. At £120, i dont want to do it needlessly. I've checked all grounds, fuses and changed dist. cap and rotor arm.

I cant find the wires to the oxygen sensor!!!!! or the sensor itself..its not on the cat.

please help to make my porcshe complete, thanks




Migration info. Legacy thread was 25580

 

[Used Porsche]

Book it in to a Porsche specialist (not a Porsche dealer)- they will solve it in no time.

Migration info. Legacy thread was 25585

 

[Matt]

Check all the hoses round the back of the engine for any splits, loose connections, only takes a small leak to upset the mixture.

I have a 3.2 carrera that did the same, found a rubber pipe was split round the back of the engine (very difficult to check!!), then had the mixture re-set and the airflow meter recalibrated, it hasn't stalled since, although it does still hunt slightly when cold. There has been a few posts on here about it, seems a lot of 3.2 carreras do the same, due to the age of the cars it is very hard to cure - could be dodgy connection, perished rubber, faulty sensor, list goes on... or any combination...

If it idles fine when warm then I don't think it will be the idle valve.


Migration info. Legacy thread was 25586

 

[imported_Trev Jaso]

its all fixed..............i realised that the original cylinder head temp sensor was of the old type with only one wire and terminal thus sending an inacurate reading to the ecu............thus idling was eratic. Simply installed new one and all is now well.



for info...thansk guys


Migration info. Legacy thread was 27734

 

[Tiptop Topcat]

Wish I knew that much about cars and their mechanics.

The interesting thing is that I read about this problem somewhere else recently. it was reported as anot uncommon problem and difficult (costly?) to track down. Well done Trev for finding and posting the solution.

:lol:


Migration info. Legacy thread was 27749

 

[anil999]

Hi Trev



I have exactly the same symtoms as you on my '88 3.2 Carrera.

I am about to replace the rubber hose going from the rear of the throttle body to the Ambient Air Valve as it appears to be cracked, hoping this would help. However, if it doesn't, how difficult is it to replace the cylinder head temp sensor with the new updated part?

Cheers

AP


Migration info. Legacy thread was 28031