Joao Pacheco

Hi to you all, i'm writing from Portugal and i'am a newbie in the porsche world. I recently bought my first Porsche (1991 964) and among other questions i am dealing with a strange idle and oil pressure variations (cold and hot engine). In cold the car almost goes off if i make some acceleration and with hot engine the oil pressure varies between 1,5 and 2 and idle between 600 and 1000. If i make some acceleration the oil pressure goes to 4,5 but if i take my foot suddently it goes below 1 and the rev goes below 500. Later i will attach a video (after 20/30 minutes drive) hoping someone can help me figure out what can be the problem (ISV durt, Battery, etc). Hope to hear from you as soon as possible. Best regards, JP

964Andrew

I found the oil gauge behaviour depends greatly on oil pressure sender. My old OEM one would be very slow to move but very consistent. Aftermarket oil pressure sender was very jumpy, it would read 4.5 then 0.5 then 3.0 then back to 0.5. All in a space of one second. Oil pressure light would not come on thou. I have finally put in a brand new OEM pressure sender and it behaves normally. It does vary between 1.5 - 2.0 when engine is hot.

Thanks!
Andrew

Joao Pacheco

Hi Andrew,
My oil pressure varies between 1.5/2 when its hot. The problem is some oil pressure variations combined with idle variations. When i decelerate the tachometer goes below 500 and the oil pressure below 1. Is that a normal behaviour? I am new at this.
Thanks a lot,
JP

Joao Pacheco

Here is the video link:

964Andrew

This looks exactly like what mine does. Your RPMs drop a bit lower than mine and in result the pressure drops below 1. Last year my iddle was irregular, so I removed the O2 codding plug from under the driver seat and did not have any problems with iddle since.

Thanks!
Andrew

cobalt

To begin with congrats on the purchase.

The idle looks like you might have a light weight flywheel possibly without a chip. These cars idle will fluctuate with one. It is a faster revving engine like the older 3.2's this way but if it is not done properly can be problematic. Does the car stall if you turn on the A/C?

The sound and rise of rpms on the other hand makes me question if you have the LWF. Does it sound like someone dangling chains when running and you are behind the car. they usually make a noise like this.

It also seems as though the sender might not be factory as Andrew said.

My 93 will usually be solid at 3 when warm and will drop down below 3 when warm and driven hard or long periods but never gets to 2. At WOT it will be a solid 5. But these cars will vary. So you will need to learn it's quirks.

If you haven't had a mechanic look it over it might be worth having one do so. I always replace all fluids and inspect everything ASAP after the purchase of any used vehicle. It is expensive but worth starting with a clean slate you can trust.

GL

budge96

Hey Anthony ! great seeing you day before yesterday at hershey thanks for taking the time to find our spot..
To the OP the response of the oil pressure gauge appears pretty routine to my experience , I would suggest as Tony mentioned try checking the oil levels, changing the viscosity and filters and start fresh with
oil you know is a certain grade and viscosity.
This will allow at least a more knowledgeable point of reference and some degree of comfort...Bert

Joao Pacheco

Hi Andew,
Thanks for your answer. Sorry for my ignorance but can you please tell me where exactly is located the O2 codding plug? Thanks

Joao Pacheco

Dear Anthony,
Thanks for your kind words. I bought the car a week ago and its a dream come true.
I did not find any sound like you described but i am not an expert in Porsche sounds.
Can you explain me whats the problem if the car has a LWF?
Its a little bit strange but the AC seems is always active.

Regarding the sender, can it be replaced with low cost?

Can i ask you something: can it be durt in the ISV?
Thanks a lot for your attention,
JP

964Andrew

Under the driver seat you will find a brightly labeled plug (only California cars). When I removed it, it helped with my idle. I'm sure there are much smarter people here who can explain the open to closed loop fuelling tables and O2 sensor monitoring.



I have the factory LWF (89 model year) and heard those cars are prone to have irregular idle.

Thanks!
Andrew

Joao Pacheco

Hi Andrew, no O2 plug. But my car is a WP0ZZZ (europe). Attached is a image under the driver seat.
Thanks a lot.
JP

Joao Pacheco

Anthony, here is the link of my car engine sound: The car doesn't fail when i turn on the AC.
Hope i can hear from you soon.
Best regards,
JP

cobalt

I wish I had more time and nicer weather to chat. Always fun hanging with you guys. There is always something going on. LOL I was sorry i missed you guys last year. You had left by the time i had packed all my junk up. Lets hope it doesn't rain again next year but it usually does.

You made a great choice. the 964 is a great ride and apparently the best platform to turn into whatever you want or keep it as is.

Listening to your clip is hard to tell but it doesn't sound like you have a LWF. Nothing wrong with them although some people have problems with stalling when just the LWF is installed. Usually it requires a chip to compensate for the loss of reciprocating mass associated with the DMF.

I have a LWF in my C2 and i prefer it but some like the car as is.

As I said each car has its own personality and I always see variations from one to the next. So it takes some time to say what is right for yours or not. So long as pressure continues to build under WOT you should be OK.

The A/C is always active or the fan is always blowing? On the earlier cars IIRC the front blower fan runs constantly at low speed and will speed up as you change the settings. if the A/C compressor is always running that will need to be diagnosed. Also you might consider seeing if all of your servos up front are working. These have a tendency to fail from corrosion over time.

Nothing is all that easy to get to on these cars especially the oil pressure sensor and you will find out not much is cheap. There are many DIY projects beginners can do and if you are experienced it is just reading and learning and taking the time to do it right. Independent mechanics will run you between $90 and $150 and hour in the US not sure what it is like by you so little things add up quickly.

I can't say what if anything is an issue without being there to see what is going on. I have a friend who always calls me with questions and I try but without having the car in front of you it is easy to lead someone down the wrong path.

If you want to tinker you might start with the fluid changes and picking the oil that you will always be using and see if anything changes.

I understand cost is an issue but having an independent look the car over and give you advice is not a bad staring place. It will cost for the diagnosis and then you can decide to have them do it or you can try yourself. There is a wealth of info both here and on Pelican. These cars aren't getting any younger and it takes time to learn all their quirks but that is part of the allure. There is nothing wrong with checking everything out and cleaning as you go. The car will appreciate it. Just don't rush the project and these cars are pretty straight forward.

Good Luck

gchristofi

Oil pressure seems ok and varying with revs. Perhaps idle adaptation is the way forward if not done already.

https://rennlist.com/forums/964-foru...daptation.html

Joao Pacheco

Hi Anthony,

Thanks a lot again for your attention.
What i was trying to say is that the fan is always working, not the AC. But next week i will check it with a independent mechanic (Porsche specialist) and see if anything is wrong.
I have a passion for classic motorbikes and its much more easy to understand what is right and wrong.
Can you recommend a engine oil to this car (15w40?? 20w50??)?

Best regards,
JP