Is this normal?

[1970BOB]

Is this normal?

I just got a 1988 911 3.2. After accelerating and taking my foot off the gas to come to a stop. The RPM’s drop to 700 or so, bounce to 1100 then slowly settle to idle at 850. Is this bounce normal, or should the RPM's stop at 1100 and settle to idle?

[87coupe]

Sounds like the Throttle Position Microswitch might not be working right. Check the cables and position of the switch for starters.

[450knotOffice]

When you release the throttle on a DME equipped car the injectors stop injecting fuel (to save fuel). At a predetermined RPM (I think it's around 1000 or so) the injectors fire back up in order to slow down the RPM drop, and then the engine will settle into a normal idle.

Why the engine would drop all the way to 500 or so before the injectors fire up again is beyond me. However, I had a similar situation arise. After a lot of fiddling with various components, I finally decided to bring the car to the Porsche shop I use and asked them to adjust the idle mixture and idle speed, both of which are interrelated and crucial for a DME controlled engine. After they did that, the car ran perfectly, and has ever since.

You might check your ISV (Idle Speed Valve) for proper operation before you take it to the shop though.

Do a search for this problem on this forum. There is a lot of good info to be found. Try something like "erratic idle".

Good luck.

[livi]

I just sooo amazed with this place !!!

You will have people respond things like:

- Sounds like the Throttle Position Microswitch, or
- Might wanna look into your Idle Speed Valve...

..and I go: What in theee h%&¤¤ are those gizmo's ? Where are they located and what are they good for ??

I bring out my Bentley´s, Wayne´s 101 and start firing away stupid questions on this board.

No wonder the waiting room´s still crowded with crying kids 3.30 in the morning when I´m on call..

[1970BOB]

bump