Mart993

Hi Everyone,

Vacuum changeover valve is clicking at the same time as the shake is going on. Voltage on the plug to the changeover valve is steady when disconnected, however when connected it fluctuates in time to the hunting with the changeover flap moving in sympathy. Anyone had this fault - from the circuit diagram its either a faulty valve, something triggering the ECU to open the valve, or the ECU itself.

Before spending another small fortune on an ECU, has anyone nailed this fault before?

Many thanks

Mart993

Timspu

Mart993,

The car is Amarant Violet (Deep Purple).
Best of luck with your hunting issue. Hope its not too expensive

TIM

Bopper 993

My '95 Carrera has "surged" from start up for an average of 15 sec. Or so! It bounces up and down from 500 rpm to 2,500 rpm. Eventually it smooths out however the idle is very inconsistent and at times the engine will completely die. I find this extremely dangerous - mainly from the possibility of being "rear ended" at stop signs/signals. Additionally the power assisted steering goes out with the accompanied difficulty of negotiating tight turns.

I have had the car worked on (3 times)by one of the premier Porsche shops in Ct to no avail. They were able to lessen the surging phenomenon but the problem still persists.

Any suggestions?
Bopper993

techman1

Bopper, do a search using the "Search this forum" tool in the top right of the main page. Look for ISV or idle stabilizer valve. Sounds like your needs cleaning, or is defective.

nine9six

I would certainly want to get both intermittent issues addressed as well. Maybe the intermittent fuel pump (DME) relay is part of your problem?

d ward

Quote:* Mart993 06-26-2010 10:17
42 Fuel pump relay
Intermittent
Present
Short B+

45 Check engine warning light
Intermittent
Present
Short to B+

According to the engineer, everything else checks out ok but he could see a valve hunting backwards and forwards as the idle tried to lock on.

hopefully the op's engineer found the fault, he's had nearly 5 years to find it ;-) :-)

bobs95

RDS928S, how'd you fix your 993? My '95 is doing the exact same thing--only happens when the engine is cold and air temp is colder. Lasts 5-10 seconds and then goes away. No warning lights while it's hunting, and runs fine afterwards.

nine9six

Damn thread post dates...If I could only remember to check em!

BobbyT

Maybe resetting the "Idle Adaptation" might cure idle surging...

From another posting on related topics: "Now what is an Idle Adaptation? Well, as far as I understand it, the adaptation is like a hard reboot of the DME's idle function, so that it returns to factory baseline settings. For some funny reason, you can unplug the battery and walk away from the car for a week, but the DME still will retain the idle settings it's "learned". The only way to reset it, is to do it via the diagnostic port..."

This is done with a laptop computer, Tore's OBD connection, and free Scantool software. I have this setup, but I haven't needed to do an idle adaptation yet. I can PM more details, also copied from the earlier post, if anyone needs.