marcar
Very sory for the delay but work keep me away from the forum until now (9:15 PM E)
This entire system of switches, sensor's, vaccum lines etc. etc. work toguether as a unit, and the logical purpose is to calibrate constantly the mixture of the engine. Our modern 911's car's began using the (electrical) and computirized components that control the mixture and at the same time control the emmisions from the 1980 to date.
When this system is ok no problem, but when they cough, the diagnostic is very difficult sometimes.
The previous details came from my experience and data gathered from different resourses such as Bentleys,Solving BOSCH CIS Problems among the great resources of this host forum . Jhon Walker a Porsche mechanic in Seatle WA, and member of this forum is a great help.
My friend ..., take it easy and don't rule out all items to be check. Even a "rusted cable tip" can ruin the efective operation of a component becoming a resistor instead of a conductor.For instance the OXS sensor only delivers millivolts
( from (.200 to .999 vlt) and the frequency valve FV get's ground fluctuations for the proper operation. I hope I can be of some help..!
Keep in touch

Cordially

VicSmileWavy

In regards to the switch Pix that I send you before,this is the Trottle Asembly Alarm Switch

VicSmileWavy

vic i,m curious
can all those settings you,re telling him to check be effected by adding a bottle of techron to the fuel tank

i don,t mean to offend i,m just trying to understand your logic

lonewolf

Just trying to help..!Not offend.
Every day is a good day to learn something new..!And I don't have all the ansuers

Vic

vic , not offended. i meant my comment to you were not ment to offend .
my point is adding anything the your gas cannot change a mechanical fixed setting. in other words the screws don,t mysteriously move in and out just by adding techron to you tank.
a clue is under light throttle it runs fine
under heavy throttle it bogs . it bogs because it is loading up the system because it can,t get out the injectors quik enough because they are clogged .
if you put techron in and everything runs fine that means all electricals are in order as is the ignition system ect.
techrons purpose is to clean injectors so buy having it in the fuel system it is helping the engine run ok by allowing the injectors to produce to proper atomization.
without it the quikly clogs up again to the point where it will run but not 100%
+ it is a lot easier to check each injector for the proper mist than to fool around with all the injection settings.
you pull and injector out and test the spray pattern and put it back in ., you don,t hurt anything .
messing around with all those critical injection setting especially when it,s your first time doing so can perhaps do more harm than good.
porsche had an article over 7 years ago suggesting the use of the techron additive for this very reason.
allways start at the beginning and see if you are getting adequate fuel delivery at the injectors . if your not then try to find out why.
if not the injectors then some other part of the fuel delivery system is clogged at least thats my guesse based on him saying it only runs good with techron added.
if there is something he,s not telling us then it,s a whole different kettle of fish.

lonewolf
I definitively agree with you...! I'm assuming that he performed a spray patern test and a presure opening test in all the injectors. The atomisation patterns and the opening of the injector has to be between 50 and 55psi that is the tolerance. If he didn't "Marlin' is losing his time, and all the above info is useless.

VicSmileWavy

Try a richer setting. I think JW recommends 3.5% with a meter at the exhaust end.

marcar,

Several of us have mentioned that you may need a richer setting, but I haven't read if you have tried that yet.

Where is the adjustment to richen the mixture?

Rich Franco
1980 SC Targa

Between Fuel distributor and air flow sensor plate housing. It is hidden on the bottom of the above. Look for a small hole which may have a plug. It requires an extra long 3mm Allen key and should be done with an exhaust O2 analyzer. The adjustment screw is inside the small hole and you may have a plug covering the hole which needs to be removed. If you are not sure about the adjustment, let someone do it who knows. You don't want to screw up here.

As Gunter says, if you are unsure, have a mech do it. It only takes a couple of minutes. If you watch, then you will know what to do if you try it yourself later. JW recommends a CO setting of 3.5% If the idle speed fluctuates then the setting is too rich.

Instead of sprays to test for vacumne leaks try a small tube connected to a propane bottle. turn the propane bottle on and take the tip of the felxable tube and run it around the areas you want to check for leaks. The engine speed with increase becasuce of a richer mixture and not introduce materials not ment
for combustion.

Keith Epperly
87 slant nose turbo look carrera cabriolet

I didn't read anything about what happens when free reving the engine slowly and very quickly.

I assume fuel mix, plugs, and the wires + Beru connectors have been confirmed to be good. A timing light confirmed dizzy curve? The ignition wires have been water bottle sprayed in the dark? The CIS has been psi ga tested?

maybe you need carbs :p

thanks noah
some people just don,t get it

Made some gains on the issue last eve with the stumble / breaking up issue. I read a unrelated post describing a similiar issue where a 964 second coil was removed in the diagnostic process allowing the engine to run on just one distributor. The result was detonation / breaking up if memory serves. Makes sence as Porsche dual systemed to promote combustion. This lead me to start to sort through the iginition side of the equation. If nothing else to take a break from the fuel side of the issue. I will get back to the fuel in an effort to still improve performance.

Inition - Validated:

1. Plug wires - all displayed correct ohm values and hence continuity.
2. Coil primary and secondary valuies within published specs.

Next went after the plugs. Found all plugs to display an effective gap, though prior gapping or just wear, of .042" to .048". Spec. on the plug gap is .031 (NGKs). This larger gap is potentially too large for the CDI to handle efficiently over all pressures and temps.

After the plug change, I gained a smoother stronger power delivery with the heavy stumble/break up not present as before without the Techron. The Techron must have promoted combustion in some fashion in the presense of the weaker spark. Without this catalyst, heavy misfire under load appears to be the result.

Unfortunately, back to the original post, the light detonation with throttle is still present. Could be carbon, injector flow, etc.

Next Validation Efforts:

1. Will check individual injector flow. Presures and WUR already validated.
2. I am still running the O2 sensor / Cat and would like fatten the mixtue to the 3.5 percent referenced numerous times throughout this board in an effort to control detonation assuming all else is OK. Will this harm the cat? And, I am assuming you cannot get close without a Gunson.

Could one potentially use the O2 sensor (before unplugging it) and approximate the resultant mixture though the reading the duty cycle (dwell)? In this case, the rich mixture would be expressed as a dwell less than 45 degrees (50 percent duty) as the system leans in response to the mixture screw setting. I have read 2.5 percent CO equates to a dwell of approximately 25 to 30 degrees.

Does anyone have experience with this method or is it too imprecise.

Marlin

what happened to the dizzy advance curve check?

Read Charlie's post. It's the 5th one down. I've never done it using his method. Charlie has credibility in my book. I would have tried it if I still has a CIS. The Gunson was accurate in my experience with it. I compared it's reading right after being on an expensive 3gas machine.

http://forums.pelicanparts.com/porsche-911-technical-forum/212120-adjust-mixture-now-i-have-tool.html

I did validate the vacuum advance unit and mech advance of the distributor. The vac advance appears to pull the timing up - diconnected is at 5 degrees BTDC as per spec.

I did not get a chance to unhook, advance though the body position, and drive test drive.

It is my understanding, this vacuum line retards the ignition - correct? Thus, opening the throttle (decreasing vacuum) would advance the timing (quickly) in response to throttle to aid in throttle response.

Will check it out.

In the above post, I am posing the question if the method of setting the CO with the O2 sensor and associated duty cycle command (dwell) is an an accurate method.

Marlin

don't know

fixed?

I am lost now. I thought that dwell angles only come in if you have points? SCs don't have points. Enlighten me, how does the duty cycle of the FV compare to a dwell angle and how does it relate to any potential problem?
There are two vacuum lines on the distributor: Advance and retard, which line do you mean?
When you open the throttle, the vacuum advance sets the ignition earlier, the retard line is part of the emission control on decelleration I believe.
I only use Techron right before an oil change; the car should run alright without it. There is something else not right if you need Techron all the time. :rolleyes: