Sportomatic needs to idle a few minutes

[Sharkbitemarky]

Sportomatic needs to idle a few minute before perfect shifting.

If I start up from cold it's a little difficult to shift between gears.

Once off the drive and under normal driving it's perfect.

Idle Vac is ~15 Hg, max Vac is about 20 Hg and looks like the system holds Vac.

Could it just be the Vac resevoir/accumulator just needs a few mins to fully build its Vac and is this normal.? or something else ?

[Sharkbitemarky]

Bump

[Schulisco]

I'm not into the Sportomatic, never seen one personally. BUT: There's a chapter in Haynes Workshop manual for the 911 including an fault table. This is all I know the only book on the market covering the sportomatic.
https://haynes.com/en-us/porsche/911/1965-1989

Also the Sportomatic of the Porsche 911 is in general quite similar to the half automatic gearbox of the VW beetle. And VW provides the workshop manuals electronically for free, unfortunately in german only...

https://www.volkswagen-classic-parts.com/content/dam/global/de/content-images/02_service/reparaturleitfaeden/reparaturleitfaden-kaefer-1975-1985/repleitfaden_typ1_85_seiten_156_204.pdf

https://www.volkswagen-classic-parts.com/de_de/service/reparaturleitfaeden.html

Thomas

[93nav]

I am not positive, but I do not think having to idle a few minutes is normal. I do not recall ever reading anything stating this.

Have you checked your oil level? I recall reading a long time ago that low oil levels will cause problems, though I forget what kind of problems.

The Haynes Sportomatic troubleshooting section (page 145??) did not cover your scenario.

How, and where are you getting your vacuum readings?

Let us know what you find out.

[Schulisco]

I read several threads in the past on the web that most problems of the SPM are caused by vacuum leaks. And after second reading this could also be the issue in this case because it takes some time to produce the required amount of vacuum after engine start...

Thomas

[icarp]

The gearbox is still a gear to gear type of transmission, It is in fact an automatic stick shift.
The gearbox oil must be fresh, The vaccume lines must be leak free and the linkage must be adjusted well.
Simple stuff, just go down the list
Ian

[Matt at Pelican Parts]

I tried to do some investigating and looked through the technical articles and although I couldn't find anything specific to the Sportomatic, I did come across one for shifting improvements. In the comment section Nick mentions that if a Sportomatic has trouble shifting even when off, it might need bushings, Though I do understand you're leaning towards it being vacuum related.
You can find that article here:
https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/37-Shifting_Improvements/37-Shifting_Improvements.htm

Also, digging through some old posts on the subject I found this one has a few handy diagrams:
Help Porsche 911 Sportomatic

-Matt

[Sharkbitemarky]

Originally Posted by 93nav

I am not positive, but I do not think having to idle a few minutes is normal. I do not recall ever reading anything stating this.

Have you checked your oil level? I recall reading a long time ago that low oil levels will cause problems, though I forget what kind of problems.

The Haynes Sportomatic troubleshooting section (page 145??) did not cover your scenario.

How, and where are you getting your vacuum readings?

Let us know what you find out.

Oil level perfect and oil new, getting vacuum reading by "T" ing in to vacuum hose between inlet manifold one way valve and Vac resevoir.

It's definitely feels like Vac resevoir needs to fill with Vac ! fully before moving off, otherwise why have a resevoir ?

As far as I can tell the system holds Vac, also once on the open road under any driving conditions works perfectly.

A thought I did have is the one way valve restricting the rate at which vacuum can be produced.!

[Schulisco]

Guess only with a smoke test tool or even a leak detection spray / soap water in spray bottle you can identify a possible leak...

Does this happens every time you start the engine or when its cold only? Those systems are never fully sealed, they will loose vacuum over time and it's only the time which separates a sealed system from a leaky system...also for example on the CIS of my SC: Residual pressure with new fuel accumulator, new injectors, new fuel pump (incl. new check valve) and renewed hoses takes hours to loose pressure. With the old stuff it hold the pressure not more than half an hour (which is just about within the Porsche specifications...)

Thomas

[Sharkbitemarky]

Originally Posted by Schulisco

Guess only with a smoke test tool or even a leak detection spray / soap water in spray bottle you can identify a possible leak...

Does this happens every time you start the engine or only when its cold? Those systems are never fully sealed, they will loose vacuum over time and it's only the time which separates a "sealed" system from a leaky system...also for example on the CIS of my SC: Residual pressure with new fuel accumulator, new injectors, new fuel pump (inlc. new check valve) and renewed hoses takes hours to loose pressure. With the old stuff it hold the pressure not more than half an hour (which is of course slightly in spec of Porsche...)

Thomas

Good question re does it do it on both Cold and Warm starts. Only seems like the first start of the day, never noticed it after a delayed restart within the same day. Will check this.

[72_sporto]

Only just saw this thread. I've had my 72E sporto over 30 years. It should shift almost right away. Certainly within a minute of starting. Maybe a small tear starting in the servo diaphragm?

[Sharkbitemarky]

Originally Posted by 72_sporto

Only just saw this thread. I've had my 72E sporto over 30 years. It should shift almost right away. Certainly within a minute of starting. Maybe a small tear starting in the servo diaphragm?

Thank you