Poor Running Without Techron in Tank

[marcar911]

I am currently experiencing severe drivability issues without the use of Techron added to the tank on an 82SC. With Techron added, the engine seems to run better if not fine thorugh the RPM range.

Without Techron in the tank, the problem is as follows:

1. With light throttle (slow roll on), the engine will easily run through the rev range (to 5000 RPM)

2. With medium throttle application (faster roll on up to approx. 1/2 throttle), the engine either detonates briefly or heavily stumbles at approximately 3500 RPM then continues up the RPM range.

3. With heavy throttle application (fast roll on, 3/4 to almost full throttle), the engine will heavily breakup and loose power at 4000 RPM to 4500 RPM. I have been unable to verify if the engine will recover with the throttle down after the breakup period. At this point, I am usually forced to let up.


The problem appears to be throttle/RPM dependant and is repeatable. To date, I have:

1. Checked all working CIS pressures. Appear OK.
2. Verified Timing as correct. Verified timing at 4K. Newcap, rotor, and plug wires.
3. New Fuel Filter.
4. Verifed O2 sensor and associated support circuits are functioning. Warm mixture set to achieve 50 percent duty cycle.

I am unsure if this is fuel or ignition related. I am assuming the Techtron boosts the octane rating but I am failing to identify why this improves (or masks) the issue. Short of running Techron all the time, I am out of ideas.

Assistance is appreciated.

[FrayAdjacent911]

That sounds right off like a vacuum leak somewhere. I would think a leak would be more severe as the throttle opens more and more.

Just a thought. I'm still just a n00b. The experts will chime in any moment. I'm sure. Any moment.

[no substitute]

Are you running too lean perhaps?

[marcar911]

The idle is not elevated. Fairly steady at 950rpm. The idle RPM is able to be influenced through idle adjust screw on the trottle body. If a leakof sufficient volume is present, would the idle screw still respond?

I will monitor the vaccuum and duty cycle while driving to see if I am leaning out.

[vizail]

Every day you learn more and more with Porsche Mechanics.
Vacuum leack's is a ,ust check. A well known test is to get a can of carburator and choke cleaner and spray around the sleeves, air box, injector seals , pipes. etc.etc. Even tha vacuum hoses have to be replaced after some years.
When was the last engine rebuilt (if any).How many miles in your engine and not changing the above items.
How about your Ignition distributor? Maybe is time to be replaced or rebuilt. Maybe the vacuum advance diaphram is defective or leaking. An experiment..! discomect the advance side of your distributor(vacuum) and plug it, then advance the ignition dist. 5 o10 deg. and run around for a while. Check the internal parts of the ignition Dist. and look for rusted and dry grease, stuck parts. Some grease should be present in the dist.
Let us know if the test Work

Cordially

Vic

[marcar911]

Vizail,

The engine has not been rebuilt to the best of my knowledge.

Odometer just turned 56 with most items in the engine bay original.

The distibutor responds to the vaccuum advance being removed and applied. Mech advance appears to be free.

I will try the carb cleaner test. I am assuming RPM will drop.

Removing oil fill cap causes RPM to drop slightly with duty cycle rising to 80 percent. Is this normal thinking through vaccuum leak and air intrusion scenerios.

[vizail]

marcar911

As discrived in the Waynes 101 Projects, page 96 , Tuning and Adjusting CIS FI.
To check for Vacuum leack's spray some Carb Cleaner or Starting Fluid to the Intake runner Sleeves, Injectors, seals and vacuum hoses and plastic components. If the engine idle speed will increase slightly you hace a Vacuum leack, if engine speed increases and then stal's your engine has a mayor Vacuume leack. You have to track down the leack and sometimes is very tricky to find one. Try to have a Fire Extiguisher just in case. Don't be afraid to perform the test. Just Make sure that you don't have a some sparck's running around your dist. Cables .

Cordially

Vic

[marcar911]

Thanks,

I will be looking at the AAV, AAR, and all points of potential vaccuum leaks today in an effort to hopefully pinpoint the problem.

Marlin

[Paulporsche]

Have you tried richening your mixture?

I see you are in the midwest. Was your car put away all winter?

How much Techron did you use? Was it in a full tank? How many miles have you run w/ the Techron?

[marcar911]

Paul,

The car was away for the winter. The issue was present in the fall.

The Techron was added in the concentration recommended on the bottle instructions. I additionally have utilized Techron in lower concentrations than recomended with the same results. I have ran with Techron in varying concentrations most of the past year. The car is daily good weather transportation.

Marlin

[stefang]

Throttle Position Sensor?

Stef

[Paulporsche]

Sounds like a lean condition. Could be leaks or WUR. It might just be the mixture.

[marcar911]

I too believe the problem to be mixture related.

At what point does the throttle switch for WOT get engaged? It is my understanding the WOT switch drives the frequency valve to 65 percent to richen the mixture.

Has anyone had the throttle switch fail and what were the symptoms?

I plan on running a trial pulling the lead to the 15 degree temp switch to GND - forcing the fixed elevated frequency command and see if this helps.

Have not got the issue fully solved yet.

Marlin

[vizail]

The Switch Closes one set of contacts at Idle to just off Idle, closes another at Wide open Throtle.

The second Switch closes at Idle

I recommend the following Page..!
<http://www.members.rennlist.com/jimwms/CIS/CIShome.html>

Cordially

Vic

[marcar911]

Vic,

I am assuming there are two switches in a common housing on the side of the throttlebody.

Where is the second switch you refer to. There is a second micro switch screwed to a plate that is acuated only when the throttle is closed. This switch has two wires: brown and green going to it.

The link is not acessable. Please check as I welcome the material.

Thank you

Marlin

[vizail]

marcar

Sorry about the link.. let's try again.
<http://members.rennlist.com?jimwms/CIS/CIShome.html>

My mistake in the site address.
Here is the switch in my car. One can check if this is working properly with a continuity tester. atach the + to one side and - to the other an the meter should "beeeeep".
But let me tell you I don't think this switch in particular has to to with your problem.
The other switsh is licated between the Airflow PLate and the acceleration assembly,, under the boot This partucular swith is more relevant to your acceleration problem.



Furthermore the Trottle position Swicth will give thre(3) different signals: throttle closed(idle) wide open throttle, and anywhere in between. This allows the ECU to makes its programmed mixture adjustments based on the trotle position.

There are three pins on the throttle switch electrical connection. Looking at the connector that plugs into it, one socket goes to pin # 18(ground brown) the other wire is a green / red that goes to the T12 Connector/pin 10 to the Acceleration Enrichment Control Unit and then to the ECU, the next wire is a Blue /white that goes to T12(pin #9) to the ECU. One is the Idle Circuit and the other is the WOT circuit. Make sure that you check the continuity between the T12 Pins and then to the ECU.

Now use an Ohmmeter to test the operation of the switch. In the Idle position there should be a continuity between the idle terminal and the ground terminal, wish goes to open as the throttle moves off Idle. In the WOT position there should be continnuity between the WOT and Grond,.. wich goes to open as the thrittle moves back to its mid range.
The relation of the Throttle switch betwenn itself and the throttle baffle is adjustable using the two screws wich mount it to the throttle body. With your Ohmmeter in the Idle Circuit Possition your switch should be adjusted so that the circuit opens just as the throttle comes off Idle( there is usually a pronouced "click" that can be heard at this point) If this adjustment cannot be made,or if the throttle swich does not respond to the previous test, it must be replaced.
Do not ruled out oher potential problems and remember to check the wires continnuity and delivery of Ground and Corrent(signals + or - )



Cordially

Vic

[lonewolf]

techron is a fuel additive designed by chevron .
chevron fuel allready has techron in it .
it is not an octane booster
think about it logically. if you put a can of that in and everything runs fine that means all your electrical ect is fine
don,t overthink it .
techron.
it,s purpose to keep injectors clean , have you tested your injectors for spray if they are not an even conical mist then they are dirty

also removing oil cap will make rpm,s drop. thats normal.
thats why a little thing like a poor seal on your oil cap can effect performance.

[kang]

By the same logic as lonewolf, perhaps you have excessive carbon deposits in the CC's?

[marcar911]

Vic,

Thank you for the detailed information. I will check out the switches using the methods outlined.

Will go after the injectors next.

Will keep attemting to track down the issue.

and, thank you to all who have provided info so far.

Marlin

[marcar911]

Vic, All

What is the pupose of the Micro switch - the one not on the throttlebody with the green and brown wires?

This wire appears to go to pin 6 on the control enrichment module and pin 6 on the ECU (oxygen contol unit).

Marlin