jadh

Procedure very clear! It is perfect! The french name for ISV is Actuateur de ralenti. I have already cleaned this part 2 years ago because of instable idle at cold.

Thanks a lot for vids!

ras62

Does it smell like the engine is running rich i.e too much fuel?
I would check the small vacuum lines going to the fuel pressure regulator, the vacuum valve and also the accumulator chamber on the back of the air filter box.
An easy way to check if vacuum is ok. Run the engine and then turn off. Get someone to switch the ignition switch to the 'on' position while you look in the engine bay to see if the resonance valve cycles. If it does then vacuum piping is ok and the fault lies elsewhere.

jadh

Thank you,

What do you mean by " resonance valve cycles" : I will hear a noise or see something?
The procedure is : I am at the engine bay, someone on the driver seat cut ignition and then turn back the key to "on" position. Then I check resonance valve cycles...true?
I can do this with a cold engine (no nead to be at service temp)?

ras62

Yes jadh, just start the engine to make sure a vacuum is there then the valve should move the next time the ignition is switched on. The resonance valve is a small black actuator operated by a solenoid / vacuum. It is located on the lower inlet crossover crossover but is not visible. You can hear it 'clack' and see the spindle move when stood looking at the engine.
This is the view of the valve, small black bottom left next to/underneath the throttle butterfly depending on year built.
http://forums.pelicanparts.com/porsc...-question.html

jadh

OK!
¨
Please have a look to the first video, before I start the engine, when I turn the key to "on" position you can hear a "clac" before the "beeeep" of my alarm. Is it that noise I must hear?

ras62

It could be. It could also be the electric solenoid switching and not the vacuum valve so you need to located the spindle/shaft and watch it rotate.
The only thing you need to establish at this point is that the vacuum system is ok.

jadh

Hi!

Here are some tests and results:

Test 1)
- is the vacuum system ok? How to do : just start the engine to make sure a vacuum is there then the resonance valve should move the next time the ignition is switched on. The resonance valve is a small black actuator operated by a solenoid / vacuum. It is located on the lower inlet crossover but is not visible. You can hear it 'clack' and see the spindle move when stood looking at the engine.

Results:
I made this test using a stethoscope to hear the "clac" noise in the inlet air manifold. I put the stethoscope end on the second (smaller) vertical manifold the one that has the resonance flap in it. I heard clearly the "clac" noise when putting key on the "ON" position. And when moving the key to the off position I heard again the same "clac" and a short "Pfff" like a pressure that is balancing.

-----> IS IT OK for this test N°1)?

Test 2)
- Check Idle Stabilisation Valve. How to do : Once at hot idle just pull the electrical plug Idle should stay roughly correct then try opening the throttle like in the other videos. Any different?

Results:
After pulling the electrical plug of the ISV, idle stayed roughly the same (a little bit lower). I have NOT observed any modification of engine reaction. (I made a video if needed)

-----> IS IT OK for this test N°2)

Did my car succeed in these 2 tests?
Any additional tests to perform?

Thank you

ras62

It sounds like vacuum is ok. You need to connect up the Bosch hammer tool and see what faults are being recorded.

jadh

@ras62:

Yes I will go to a specialist for hammer testing as soon as I can.

What kind of results the hammer tool is delivering? I mean, not only the default list... The diagnostic tool is also performing some tests no? But what is tested?

ras62

It stores fault codes for various parameters http://www.troublecodes.net/Porsche/
Also possible to test heater servos fans etc

ThomasC2

You can also use the Hammer for doing an "adaption" meaning reseting all the DME vaules to a basic setup including calibrating the idle. Could be worth a try.

Tou can also run a testloop of the different flaps, valves and injectors.

Thomas

jadh

Thanks for all your informations. I appreciate!

Before I go to my Porsche specialist, I would like to be more educated about the "normal" engine reaction at service temp.

Could a "Friendly 964 stock engine owner" be so nice as to post videos of his engine reactions from the engine bay and from driver seat? I am realy sorry to insist on this crutial point for me, but before doing anything on my car I want to be sure that my car got a problem (or not). That's why, for my comprehension, I need those videos.

So please I need you!

Thank you very much

Vandit

I would have done it already but the car isn't operational at the moment.

jevvy964

Ive done you a cold engine video and will get a hot one tomorrow and upload them both.

jadh

Great!

Thanks jevvy!