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Porsche Crest Throttle stop screw

Hey
I have been chasing an cold idle issue forever!
got new fuel distributor, warm up reg and lines... injectors too.
this car has been played around with allot before i bought it.
I have been wondering this for a while. what is the cm/mm measurement under the nut to the end of the bolt for a standard 911 sc 81... i think this is causing me hassle. It's the left bolt in the attached pic.

pressures are fine.. crappy start after 1 min it idles really low for about 10 min
ps: what's the measurement for the screw under the bolt in the pressure plate in the air box?

I just want to compare and see if anyone has tampered with it before i purchased the vehicle.

Cheers Chris



Old 06-09-2011, 11:16 PM
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that adjustment is not causing yor problem. just a note, the big screw above it sets the idle, not the one you are asking about.

if i understand your problem, it is hard to start (??), then it idles good for the first minute, then idles down for the next 10 minutes and idles poorly. what next, it idles up, it smoothes out but idles at the same RPM?

here is the way it should work and maybe this will help you:

the cold start valve (CSV) helps with cold starts by adding more fuel. at this time, the warm up regulator (WUR) is cold, so the control pressures are lower to also richen the mixture. the aux air regulator (AAR) is also cold, so it opens up to allow more air in to raise the idle for cold starts.
once started, 12v is applied to the WUR and the AAR. this heats them up. the WUR control pressures rise to lean out the mixture and the AAR closes to lower the RPM's. (this is what is likely lowering your RPM's after the first minute or so). the AAR can close too quickly and lower the RPM's too soon, making it run a bit rough until it is warmed up. this, along with the WUR leaning out the mixture can be what you are experiencing.

air leaks can also add to the poor runing when not quite warmed up. this will lean out the mixture even more. make sure all leaks are fixed before procedeing with anything else.

after that, as long as the cold and warm control pressure are correct, check timing and make sure it is working and set, then check the mixture, you may need to richen it just a tad.
what is the idle when warmed, perhaps a bump up of idle may help too.
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Old 06-10-2011, 05:19 AM
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exactly right hard to start, idles good for a minute or 2, then crappy for the next 10-15 min. it slowly reaches it's normal idle of 800-900. i have tried richening it, helps a bit but not much. using heaps of fuel..... there are no air leaks. got a smoke test done with everything fine about 3-6 months ago. i might give timing a go and see where that leads.
when i bump the idle up too much with the idle adjusting screw i hear a loud hissing sound.
I'd like to change all 'adjustibles' the same as another 3.0l sc and go from there. but it's hard without a 'normal setting'

chris
Old 06-10-2011, 06:04 AM
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ps: i have seen a christmas light show from my distributor/ spark plug cables recently.... could this be the issue?
Old 06-12-2011, 03:38 AM
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it aint good
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 06-13-2011, 05:05 AM
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New Update-
I have changed rotor, distributor cap, and ignition wires all brand new!
I have noticed it starts strait away most times now.. although still does the stupid low idle after a minute or 2.
i received a cis test kit. i installed it and these are my readings
start pressure WUR plugged in = 2bar
when hot = 3.5bar
system pressure = 5bar
Leakdown
0minute= 2.4bar
1minute= 2.0bar
10 minute= 1.5bar
30min= 1.3bar

what does all this mean???
Old 07-09-2011, 09:09 PM
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This looks like a early 2.7 to 3.0 conversion. Is there a thermo switch on the left side of your engine? If so is it hooked up?
Tim
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Old 07-09-2011, 09:34 PM
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There is a thermo time switch on the left front bottom of the engine... there is a red or brown wire connected (spade type) on the left of it and a yellow spade connection on the right
Old 07-10-2011, 05:22 AM
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perhaps a little more specific on the idle thing now that you have done a lot to the car.

normal start up should be a higher idle, it may be for as little as 2 minutes, for warmup. then the idle should drop to about its normal idle. it still may change as it warms up due to the too short of a hi cold idle by the aux air regulator (AAR).
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 07-11-2011, 06:56 AM
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hi CHris, were you able to fix idle issue?
thanks

Old 06-16-2012, 04:06 AM
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