Idle speed

Garrett · Post by **Garrett** » Tue Dec 13, 2005 4:04 pm

I am new to DDK, and am beginning to get to know my new and first early 911, it is a wonderful car, but I am preaching to the converted. Does the following ring any bells?

Car starts well, but when its good and hot, the idle speed goes to 2200, from 950 when warm. Letting in the clutch at 3rd or 4th momentarily causes it to go back to 950, but a touch of the throttle sends it back to 2200. Its no problem when driving at speed ( and what speed!), accelerates wonderfully, but its a pig in traffic, especially pulling from low revs in 2nd or 3rd, mad judderring until the revs go up to say 2500+, then its like a sewing machine again.

any ideas?.

Ian Donkin · Post by **Ian Donkin** » Tue Dec 13, 2005 4:47 pm

Is the distributor vacuum advance hose connected?

Garrett · Post by **Garrett** » Tue Dec 13, 2005 7:08 pm

Vacuum hose is connected and sound at all three nipples: intake manifolds and advance, thanks for your reply.

1972_911t · Post by **1972_911t** » Sun Dec 18, 2005 7:25 pm

Mighnt be worth making sure the hand throttle is allowing the linkage to go fully back when off, also that the linkage itself on the carbs if your car has carbs is allowing the butterflies to fully close.

Then move on to the idle setting, Ive never had a porsche with carbs so im not sure how this is altered on my MFI car its done by air bleed screws.

Are you having to use the hand throttle on warm up?

Gary71 · Post by **Gary71** » Sun Dec 18, 2005 8:30 pm

Hi Garret,

I guess if your car is running carbs then they are Zeniths?

If so have a read through my site (link below) everything you wanted to know (and stuff you don't!

)

Sound as if the basic set up combination of idle stops, air bypass and mixture screws are out of wack. Maybe also the overrun enrichment circuit is leaking additional fuel in when you don't need it.

Have a read through and ask away and we will try to help

good luck!

Gary71 · Post by **Gary71** » Sun Dec 18, 2005 8:44 pm

Justy noticed in your signature that your car is an 'S', so I expect that's got MFI.

Sorry run out of knowledge now!!

1972_911t · Post by **1972_911t** » Mon Dec 19, 2005 9:50 am

If you are running MFI the most important part is the paper air line that comes from the left hand heat exchanger to the pump unit, this is in two halfs one under the engine tin and one above that connects to the pump, this pipe allows warm air from the heat exchanger into the warup reg on the pump and leans up the mixture as the engine warms up, if this is torn or has leaks chances are your engine will run rich when hot.

Check this link all the MFI info you could need!

http://www.pelicanparts.com/techarticle ... TipMFI.htm

Steve

1972_911t · Post by **1972_911t** » Mon Dec 19, 2005 9:50 am

I think the best place to start would be with the air bleeed screws however to do this properly you need a carb syncronometer to make sure all 6 cylinders have the same air flow.

Garrett · Post by **Garrett** » Mon Dec 19, 2005 12:20 pm

Been away for a few days, hence delayed response...What a great bunch you DDKers are - thanks for all the expertise. Yes, its MFI. I will go through the suggestions and will respond. hopefully, to guide someone in the future.

Garrett · Post by **Garrett** » Wed Dec 21, 2005 10:17 am

It was the fuel shut-off solenoid microswitch - not making at the throttle stop: pure luck that I found it! She's running beautifully now

DDK - Die Deutschen Klassiker

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