Ignition Distributor

[opticalfuel]

I believe my distrubutor could have a sticky advance mechanism.

Is there any way to be sure if it is sticking or not, besides pulling it out and disassembling it?

If I do pull it, and try to lube the moving parts, is there a good lube to use for those parts?

I believe it gets pretty hot - so does that play a part in what type of lube you want to use on the moving parts?

Also: How best can I verify that the vacuum advance is operating as it should.

Background: The reason I suspect the distributor is that the idle after the warm up cycle is not very smooth. (The WUR seems to do it's job, but after the 2K for 2min, it falls to a 800 - 1000 idle that searches and is rough. It sometimes backfires into the intake -- rest assured though, I have the pop-off valve in place)

Thanks!

[stlrj]

Pull the cap off and give the rotor a twist back and forth. You should feel it move against the advance springs.

Otherwise, buy or borrow a timing light .

Cheers,

Joe

[emcon5]

And your car is a............? Assuming a CIS, but that narrows it down to a 10 year range.

The simplist way to check the advance is with a timing light.

If your mystery car has vac retard, unplugging the line will cause the idle to increase.

If it has both advance and retard, unplugging one should make the idle increase, and you can test the other by connecting a length of new vac hose and applying vacuum, either with a pump or your built in internal vacuum device (aka your lungs).

Rough idle doesn't sound like advance. It sounds like mixture.

WUR has nothing to do with fast idle on startup.

Tom

[opticalfuel]

Got it. I already know the answer to that. I know when I had the cap off the other day it was clear that the mechanism was rotating back and forth against the springs. That seems to be okay.

My question now is: if it seems to move okay, what are the chances that the vacuum bulb module is faulty?

Specifically: When I take off from a light, the car seems to be unwilling, till the RPMs reach about 2400 or so, then it kicks in any really goes all the way to redline.

My guess is that there is far more that could influence the hesitation than just the advance curve. I will get it on a scope perhaps. I need to call IPB Autosport and see if they already scoped it on warmup or not.

What I think is going on, in my limited knowledge is the following:

From an ice cold start:
The WUR does it's job, and after the 2K for 2min is over, it relies on vacuum and the throttle air metering: (i.e. the Fuel Distrubutor and its minor adjustments)

Then the idle is rough, and searches -- I think this must be a result of vacuum in some way, but also might be a few other things:

(remember this is a 78 911 SC)

Possibly a combination of:

Vacuum leaks
Distributor vacuum advance faulty
Dirty injectors or
Fuel filter?
Fuel Accumulator? (has not been replaced)

We recently replaced and set on the car (just a week ago):

Fuel Distributor (Bosche rebuilt) and set
Fuel Filter (within a year)
Spark plugs (NGKs, non platinum)
Wires tested ok.
Injectors replaced about two years ago

Any ideas?

[opticalfuel]

Sorry about not including a type of car:

1978 911 SC Coupe, with 3.0 liter engine,
Replaced the distributor about 18 mos ago, to a 1982 style (dual vacuum i.e. retard and advance on the vacuum bulb thingy)

Mixture can be effected by?

The Warm Up Regulator and Fuel Distrubutor have been replaced recently and should NOT be causing a problem. IPB Autosport (Ron) set the mixture and made the best effort to isolate the problem.

He said in his opinon it was some minor vacuum leak. I am inclined to believe him but after many attempts to locate the leak using the carb cleaner spray approach (when you spray a location you suspect might have a leak, and listen for idle change) hasn't turned up anything.

Does anyone have a 1978 or 1982 CIS SC that has a nice perfect idle after inital warmup?

I cannot remember a time in the five years I have owned the car that the idle has been great after initial warmup. It has always had some issue with idle. Is this just a 'feature' of the car, and should I be able to fix it?

[stlrj]

An easy way to check the vacuum diaphram is to disconnect the hose at the throttle and suck on it to see of it will hold a vacuum.

But from what you describe, it sounds more like a mixture issue like a rich bog on tip in.


Cheers,

Joe

[opticalfuel]

I'll try checking the vacuum, using the 'suck' test.

Cool. Is that test good with the engine off or only while running?

Besides a vacuum leak, an incorrectly set mixture, bad wires, dirty injectors...

What else could cause bad idle? (primarily noticable during warmup after it initally goes 2K for 2 min) It searches, fast and acts like it might die, but struggles a fair amount and recovers until it is pretty warm.

[opticalfuel]

New INFO:

I took the injectors out last night, cleaned the uholy 'crap' out of them, and put them back in.

Also: removed the Distributor (ignition) and cleaned the exterior. Also checked the operation of the distibutor vacuum advance. It holds a perfect vacuum by applying suction to the main hose on the suction side. I visually confirmed that the diaphram was holding the adjustment linkage inward, until the suction is released.

I also confirmed that the advance mechanism is quite lubricated and moved freely without any problems.

I simply lubricated it, and replaced the vacuum module.

I noticed the following PRIOR to removing the vacuum module. (right after removing the Distributor from the engine bay)

The vacuum module was somewhat loose. of the two screws that hold it in place the one farthest from the number 1 sparkplug connection was not tight, allowing for some movement by the module. I thought that this could possibly cause an incorrect vacuum advance condition:

However after securing it firmly, and after replacing the distributor:

NO noticable change in the way the motor warms up was observed.



At this point is anyone aware of any other things that can effect the idle of the car during warmup?

Note: After the engine achieves optimal temp, it seems to idle fairly well. I notice at the same time: Even though the idle seems somewhat smooth at optimal temp and idles at 1K or so:

Right off the line or with any initiation of load on the engine (barely pressing the gas while crusing) it struggles and seems to have some missing or incorrect mixture issues.

REMEMBER: I just replaced the Fuel Distributor with a BRAND NEW rebuit Bosch unit. (Therefore I expect it to be operating perfectly)

Any ideas?

[Early_S_Man]

When you replaced the ignition distributor ... how did you plumb the second vacuum port??? It is possible that your advance curve is severely adversely affected!

I suggest checking the advance curve from 900 rpm - 4000 rpm with an advance-type timing laght ... plot the advance on a graph or chart at 500 rpm increments.

Your advance curve is critical to the off-idle responsiveness of the engine!

[opticalfuel]

Understood. I know I have it hooked to the right port. It has two ports. I just looked up on Pelican's part index and noticed that they sell a new 77-82 style vacuum part for the distributor. The reason my new distributor has a vacuum module with TWO ports is because it is the only one that comes with the Distributor you can buy now. The true '78 version of the distributor is NLA.

I will make a plot of the advance curve tonight and post the results.



I can check the advance curve, but I would be surprised if it is incorrectly connected. However, I do believe there might be a fundamental diffence between the 78 version of the vacuum unit, and the one currently on the car. The old unit has only ONE port. the new one has two.

Come to think of it, I might have my old vacuum unit. I think I located it last night, but didn't think of switching it. I could see if I can swap that out.

What might be happening is that the second port SHOULD be connected to some vacuum line, but isn't because it doesn't really fit into my older style 78 version.

Right now it just have a short piece of vacuum line (about two inches) connected to it, going to atmosphere.

This is on reccommendation of Ron, owner of IPB Autosport. He believes that is the way it should be connected.

Probably the best possible solution is to have a working vacuum unit attached with only ONE port. I assume this would make it run better. Not sure.





This image shows my current '82 - '8x version of the distributor, and one vacuum line connected to it. The other end of the vacuum line connects to the port located on the throttle body, closest to the air box and CS box side of the engine. I'll add a snapshot of that asap.

As promised:



Also I am going to add a soundbite of the engine, starting, and going through part of the warmup cycle. With a good pair of speakers, you should be able to hear what I am talking about.

[Early_S_Man]

I assume that the vacuum retard port is the one you have connected ...

The original vacuum unit won't help with the later two-port version of the distributor ... the mechanical advance mechanism is calibrated differently, and needs the two-port vacuum module to have the correct amount of total advance ... throughout the rev and load range!

The '78 distributor was primarily a mechanical advance system, with the vacuum retard module only effective at idle ... for emissions compliance.

The later two-port vacuum module version distributor had less total advance in the centrifugal mechanism, plus the retard function of the former distributor, PLUS an additional vacuum advance function that was functional off-idle to redline ... for a load-sensitive variable added to the total advance curve.

Ideally, you should add a second vacuum port to your engine -- where the later '82 -'83 engines had it, and connect it up to the advance port of the distributor.

[opticalfuel]

Well to follow up, I still have not had time to make an advance curve plot, but I will try to upload a soundbite of the car's sounds.

The car runs like a champ after it is warmed up. It really has alot of power.

Just that nagging stumbling warm up. If I could solve that issue, it'd be the perfect car. Even still I can live with it. I would rather be driving anything else, even given the problems.

[Paulporsche]

Did your mechanic check your control presures during warmup and after, once he installed the new WUR? Usually a stumbling idle and backfiring during warmup mean the mixture is too lean, which could be caused by an out of spec WUR, even a new one.

It sounds like the AAR is OK because the idle starts out high and then drops after 2 min. Although you might want to check mysterytrain's thread on the AAR and the length of operating time.

Remember, even though the AAR jas dropped the idle speed after 2 min, the engine is still not warmed up until it hits about 180F.

Ask him to verify your control pressure readings.

[fredmeister]

Did you check the air box to make sure it is not cracked or leaking around the pop off valve?
Also, did you check the AAR valve piping/tubing that runs along the backside of the engine into the AAR (don't know if this is proper component name) that is mounted next to the number 2 cylinder connection of intake manifold to Cylinder head. This tubing may be cracked or bad hose connections causing a vacuum leak.
You should rule out distributor problems by running a timing light on the distributor and checking that it advances when the engine is revved. You should see a total of about 26-28 degrees advance from idle to 5500 rpm.
Sounds like a vacuum leak to me.

[opticalfuel]

Yep. I believe this is a vacuum leak. Can the leak be actually in some of the Injector sleaves?

I noticed when I removed the three injectors on the 1,2,3 cyl the sleaves came out easily, and the external o-rings were hard and seemed to be pretty squared off.

I think they could be leaking. Can that be the source of the leak?

Here is the soundbite of the engine starting from ice cold to about 3 and half minutes :

http://webs.opticalfuel.com/porsche-warmup.mp3

It's about 3.5 MB. It is easy to hear what it's doing. I am just not sure WHY it is doing it. I agree it sounds like a vacuum leak.

The easiest thing to do is order a set of seals for the injectors. So I am going to do that, replace them and report back.

[Early_S_Man]

Yes, old dried injector O-rings can cause vacuum leaks! The best clue is that they were easy to pull out!!!

You can get replacement O-rings at a local bearing & seal supply store ... take your injector and examples of the seal along with you.

[opticalfuel]

Easier yet, I can do what I just did: buy the seals at Pelican and get them in a few days. Are the ones they sell online here any good?

[opticalfuel]

According to your comments I can tell you almost with 90% certainty that the injector sleaves are not sealing. The 1,2,3 cylinders were very easy to pull loose. The seals felt very hard and looked flat.

I think it will make a good difference in the sealing of the vacuum and intake when I replace the seals. I will post the results in a few days.

[opticalfuel]

It turns out much was accomplished by simply making the correct setting to the A/F Mixture.

The following demostrates the change that was observed after making an adjustment to the Richness setting to the correct setting. When the car was brought into the shop it was reading about 16.2 A/F Mixture. It was then set to 14.6 A/F mixture which is far better.

The image here and sounds are before and after shots of the soundtrack, also linked to below.



Sound BEFORE:
http://webs.opticalfuel.com/porsche-warmup.mp3

Sound AFTER:
http://webs.opticalfuel.com/porsche-warmup-after.mp3