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Join Date: Jan 2004
Location: Sacramento
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Charlie.

You have leaking pot on your distribuitor!

Again, if your pot on the distributor is rusty and the Vac-Retard /inner side is leaking, your timing at idle will be closer to -10deg than near 0 deg as it is suposed to be. When this happens, idle jumps about 300rpm.

Dose that sound familure?

AAR failure is rpm's holding at closer to 3000rpm in full falure but they sometime start out lower.

All you have to do is pull the inside vac connection off your distributor and plut it! If the idle holds with no increase in rpm, you need a new pot.

It is starting to seem that these pots have a pattern of rusting and failing on the Vaccum-Retard side.

If the outside is rusted enough also, and is not working, you run the risk of damaging your motor when you run on boost as you will not be getting the timing retard you need.

If you do not like the simple test I recommended in post #11, you could set timing per factory spec with all lines disconnected an at 4000rpm. Then check you timing at idle. If you pot is bad you will see timing of about -10. If it is still working ok, your timing will be near zero as it should.

Good luck and keep us posted please.
Old 10-01-2009, 08:05 AM
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Originally Posted by 911st View Post
Charlie.

You have leaking pot on your distribuitor!

Again, if your pot on the distributor is rusty and the Vac-Retard /inner side is leaking, your timing at idle will be closer to -10deg than near 0 deg as it is suposed to be. When this happens, idle jumps about 300rpm.

Dose that sound familure?

AAR failure is rpm's holding at closer to 3000rpm in full falure but they sometime start out lower.

All you have to do is pull the inside vac connection off your distributor and plut it! If the idle holds with no increase in rpm, you need a new pot.

It is starting to seem that these pots have a pattern of rusting and failing on the Vaccum-Retard side.

If the outside is rusted enough also, and is not working, you run the risk of damaging your motor when you run on boost as you will not be getting the timing retard you need.

If you do not like the simple test I recommended in post #11, you could set timing per factory spec with all lines disconnected an at 4000rpm. Then check you timing at idle. If you pot is bad you will see timing of about -10. If it is still working ok, your timing will be near zero as it should.

Good luck and keep us posted please.
911st - you are referring to the distributer line which runs through the electric valve before going back to the throttle body?

When I disconnect and plug that line the idle should to drop 300 or so rpm? If it does not drop the motor speed at all then its not working? am I understanding that correctly? Should the car be cold or warmed up when I do this?
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Old 10-01-2009, 10:04 AM
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No,

If the RPM's increase doing so, it is working.

If the RPM stays the same when the vac tube is plugged, it is not working.

If it is not working it could be the solenoid but given your pot is rusty, that is probably what it is.

Another way to test is put a hand vac on the back side and see if it holds a vacuum. If it dose not, it is the pot.

Have my fingers crossed.
Old 10-01-2009, 11:20 AM
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I captured a movie of me doing the test

from Charlie Burtoff on Vimeo.



Looks to me like you are correct! Disconnecting the line didn't effect the idle at all. I have an Timing light...Maybe I should test with that now as well. I could be wrong but I didn't detect any idle increase when plugging / unplugging the line after removing it from the distributer.

I'm thinking maybe I should replace the electronic valve or at least test it before I order a new vacuum retard thingy incase I need to replace them both.

Car really wasn't up to temp, I think the AAR had closed as the idle had come down but the "hunting" or bogging only happened for a min or two before it gets warm. I drove it yesterday about 10 miles and it never stalled or modulated idle after it got warm and settled at 1k.

I'll start shopping for a new vacuum for the distributer, there is a place near me called Easy Porsche I'm gonna give them a call shortly.

Thanks 911st! You guys rock! this forum is a great resource for anyone with one of these cars!
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Last edited by Charlienofun; 10-02-2009 at 01:16 PM.. Reason: Wayne (the freakin CEO!) enabled HTML in this forum! So I fixed my post to have the video embedded!
Old 10-01-2009, 01:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #24 (permalink)
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The change in idle would be significant and about 300rpm.

Thus, your Vacuum-Retard function is not working. Rust indicates it is probably the pot.

You can take a piece of tubbing, install in on the nipple on the pot facing the dist.

Put the other end in you mouth, suck to create a vacuum and stick the end of the tube on your tong to seal it. If it holds a vacuum the pot is ok. If not you have a leak and need to send about $180 for a new pot.

Of course, if you have a cheap hand vacuum pump with a gage on it, that might be better.

You could also put a vacuum gage on the tube from the solenoid. Start the car. For the first about 10 sec you will see not vac. After that you will see vac when the valve opens.

The best.
Old 10-01-2009, 02:06 PM
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Quote:
Originally Posted by 911st View Post
The change in idle would be significant and about 300rpm.

Thus, your Vacuum-Retard function is not working. Rust indicates it is probably the pot.

You can take a piece of tubbing, install in on the nipple on the pot facing the dist.

Put the other end in you mouth, suck to create a vacuum and stick the end of the tube on your tong to seal it. If it holds a vacuum the pot is ok. If not you have a leak and need to send about $180 for a new pot.

Of course, if you have a cheap hand vacuum pump with a gage on it, that might be better.

You could also put a vacuum gage on the tube from the solenoid. Start the car. For the first about 10 sec you will see not vac. After that you will see vac when the valve opens.

The best.
911st - I put a vacuum gauge on the line it does indeed work! I was impressed.

I also hooked up my timing light and the notch is way off way center to the left, seems to confirm what you were saying my idle is at -10 no way its gonna pass a emissions test like this!

Its parked until I get that vacuum canister replaced - its to bad there is an autox this weekend but I would need to get a new battery (or make some sort of bolt down for the small one in it currently) and the rear oil line has started to leak at the junction under the passenger side hopefully I can just tighten that up and it will stop.

Charlie
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Old 10-02-2009, 03:45 PM
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A lurker here with a short story to save for the future generations..

I too had a 930 come in with high idle, 3000 or so after warmup.
Long story short, it turns out the elay for the under tank fuel pump had a bad contact. Cheap aftermarket "URO" brand red relay. In fact it fell out of it's socket when the fuse box cover was pulled off.

Car ran "ok" and when idle was adjusted down, it would hunt and surge, especially with the AC turned on. With the new relay, the idle speed went down and smoothed out, and after adjusting it to around 1000rpm, everything seems fine. The A7C doesn't drop the rpms as much as it did before either.

Engine has unknown history, someone has made a lot of modifications and the electrical and vacuum systems are a nightmare.... heh.

Anyways. Thought I'd share. Back to lurk mode.
Old 01-29-2010, 08:01 AM
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thanks Lurker .
ive been reading this post as i have similar problem with my car,,
will try the relays you never know

heck i just realised this post is 3 years old cool
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Old 03-08-2014, 09:11 PM
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