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993 C4S electrics playing-up after taking car out of storage


22 Dec 2010
Same situation as this time last year:

after reconnecting battery and preparing the car for spring MOT:

- starter sounds really fast
- it will start if you boot the throttle to the floor
- runs really rich and smoky initially for a bit, but then settles down
- occasionally when the car gets hot, ie in traffic or after MOT centre left it running on the ramp for nearly an hour, it is very lumpy and problematic and has have power reset to start it smoothly, and actually failed MOT on electrical gremlins causing brake,side,fogs to play up during the test when it got hot (I've not managed to replicate this since) - all lighting was fine last night and I checked every bulb, fuse and relay.

Same time last year the same happened, but it wouldn't start at all for while. Eventually I replaced the DME relay, cleaned the idle-control valve, checked all connections, and trailered it to LaRose Porsche in Kemsing for its service/MOT and for them to run for a week to check it out - they found nothing - it was fine by the time they received it, and fine again, even starting last summer until now, taking it out of storage where its been since the end of October.
Very odd that it clears up by itself......

I'm far from an expert on this kind of thing but:

Could it be that the petrol has gone off?

Battery lead not tight enough?

any chance that a little critter has chewed through a leccy cable somewhere?

:dont know:
I'd consider changing the battery earth strap even if it looks pristine.
It builds up resistance over time and can cause all kinds of electrical problems.
Also cheap to buy and fit , always start with the small stuff!
Re: 993 C4S electrics playing-up after taking car out of sto

Ballers suggestion is what I would do first - ten quid for a decent earth-strap?

Superlight91 said:
Same situation as this time last year:

after reconnecting battery and preparing the car for spring MOT:

I'm going to dumb this down to my level - isn't there enough of a brain in the 993 somewhere that remembers idle settings and fueling levels and so on, so if you disconnect the battery for long enough, the brain forgets EVERYTHING, so it has to learn basic fueling from scratch?

My 1989 BMW certainly does - after reconnecting the battery it will stall at every junction, do the 'hunting' thing, and idle-speed varies wildly for a few hundred miles at least.

Keep the battery connected next year, or even drive the car all year round? :grin:
OC - I disconnected my battery for 4 months this winter- connected it last week and have had no problems..... :?:
There are 'learning' ECUs and 'stupid' ECUs (ones that just take the current input signals and work with them) - I really don't know which the 993 has, and that's even after the question has been asked before.
Fuchs said:
OC - I disconnected my battery for 4 months this winter- connected it last week and have had no problems..... :?:

Same here. Left my car for over 6 months with battery disconnected and started first time. I did pull the ECU first to allow the oil pressure to build whilst it cranked and then when reconnected no problems.

I've always tried to synch my MOT with an annual service. That way they sort all the issues before the test :thumb:
Thanks for the ideas - although car appears to have settled down a bit today - when I ran it back to MOT test centre for a retest it probably didn't need (tester didn't understand the front fogs needed to be on for the rear fogs to illuminate also, and said my front LED side lights were too blue - so I've changed these back to standard). I just need to secure the rear Porsche reflector now after removing that to check the fog bulbs for no reason (ho hum, well I guess its a chance to clean behind it while its off).
Fuch's comment makes me wince with fear - particularly as I heard about a local development built on a flood-plain formerly inhabited by a lot of river-ratties. Developers put accommodation on upper floors and garaging on ground (with no electrics below dado-level) - so they are expecting it to flood at some point. The point being, and the horror story is: the critters have been found up in the engine bays of residents motors living off the rubber, plastics and wiring. Fortunately I don't live in this part of town, but it makes you think as rodents can squeeze into most garages quite easily if they want to, and I hope I haven;t got a bit of chewed-loom somewhere!
Sorry :nooo:

But still doesnt explain how the problem goes away by itself...... :?:

Maybe the car is just grumpy becasue you didnt drive it for a while :D

Hope you get it sorted soon. :thumbs:
Now its been suggested I also wonder if the fuel is going off, which do you use? Only experience of this I find is with the lawnmower which refuses to start each year without draining and filling with fresh fuel.

Could it be that the HT Leads etc are beyon their best and need to warm and dry out? Have you ever found it a bit lumpy after washing (assuming you get water down the spoiler/engine bay area). HT leads are not cheap by the time you've paid for fitting; very few owners I know have changed these (all 14 not just the easy to get to ones) so I suspect this will become more and more of an issue.

The reason I say this although I never stored my old 993 as it was used all through the year, sometimes I had some weird electrical gremlins that would kill the dials and other functions; other symptoms during this were lumpy, and in cold weather or after a good jetwashing and not driving afterwards. Many indies would change various parts, charge me, then the problem would recurr. The ONLY part I didnt ever get round to was the HT leads (everytime I asked this to be done (3 different places) all said 'we ran out of time to do them' :( )
Good point Chris.

Could just be an accumilation of moisture that burns off after a while / evaporates after the weather warms up-..

As you say plugs leads dont last forever and do internally break down.

Well worth changing them if them havnt been changed for a while....

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