burnsa

Rough Idling - almost self revving?
81/82 911SC Coupe
So having now had service, inc new clutch, MOT(UK) despite all my efforts I cannot understand the self revving symptom - and it does not go away. It will also stall with consumate ease - and although restart, it goes back to what I describe as rough idling but sounds like someone is revving to approx 1000rpm - all very frustarting. Fuel, electric, timing - any pointers would be most welcome.

Any advice would be appreciated - I am not able to return to original mechanic - geographical!!!

Also it needs driving - not coughing and spluttering outside the house!!

Many thanks if poss'...Andy
Also thanks to Brian911 in Santa B - CA, who suggested vacuum prob, but still need your tech expertise if poss

PS Apologies if you read the thread already, was/is on US/world forum too.

pjc

Sounds pretty obvious but I assume this fault was present before the service? If so what did the mechanic say? You say you can't take it back but hey the work you had done wasn't peanuts - it must be worth a few miles on the car to get it fixed. I would put the guy under pressure to fix the fault - if you trust him? If not try a local specialist. Although not exactly adjacent to Cambridgeshire, I can recommend Autofarm at Oxford if that helps (no affiliation).

Know what you mean about these seemingly unfathomable problems but I'm sure you will get there in the end.

PJC

burnsa

Thanks pjc
The problem actually started on way back from mechanic - after approx 70 miles. If there is any connection I seem to remember a faint smell of 'engine air/oil poss' in the cabin. The stalling sympton was first evident at slowing in 1st and 2nd gear, cutting out, but immediately able to restart - usually rolling into junction and taking care. It will restart from cold all the time, but it goes into this 'revving cycle' which I would say after 10 minutes starts to lessen - and the car wants to stall/stop...unless you rev yourself. On a run it wants to rev ontop of my normal drive - infuriating and obviously not right! The vacuum prob would make sense if something was inhibited i.e. fuel delivery - but if you are able to make any informed diagnosis based on the above I would be appreciative.

Oxford - ironic I bought it in Witney, but would try Autofam as its closer to me than the first one. See what you think?

Thanks Andy

pjc

Talking to a friend last evening and he had a hunting problem with his Carrera at tick-over and occasional stalling at traffic lights etc. He doesn't know what the problem was but had it fixed at Francis Tutthill at Bambury. I wouldn't like to hazard a guess what your problem could be and can only suggest taking the car to someone sympathetico to the older Porsches and have good reputations.

It may be worth chatting to Jack Philips at Autofarm, he is usually helpful on the phone.


PJC

burnsa

pjc
Thanks for this reply - will do, sounds they have a good reputation. Will let you know what's what in due course.
Ta
Andy

peanut

I have just had exactly the same problem.
I took my car to the garage to have the belts renewed and it came out hunting like mad? the revs drop to 200 then just as its about to cut out it revs itself to about 1200 then immediately dies and the cycle continues.

The garage claim they fixed an air leak on a hose to the air idler valve.
T?hey reckon the valve was gone anyway but sealing the leak has made it worse?
Also when I collected it it had the head gasket gone . A week later and the clutch broke up. ?
I guess this is what I deserve by going to a local garage without the tools and experience needed for Porsche service'repair.( It is 120 miles round trip to the nearest Porsche service centre.)
So that is where I would look first the air idler valve..You can clean them out apparently. ( they cost £128.00 ) The valve and 2 hoses sit under the inlet and I think the garage had to remove the inlet manifold to get to it.
Use a piece of plastic hosepipe to your ear to listen to the hoses and clamps to check for air leaks

burnsa

peanut
Thanks for this - very useful. Still have the problem, haven't sorted yet. Also, the engine cuts out to dead after about 10-15 mins and I guess the battery runs down too.

Incidently, full service, new clutch in Dec - the fault started on a long run, when I am pretty sure I smelt a faint wiff of oily smoke before I had to admit it wasn't good. Any thoughts or cures would be welcome, it won't run long enough to get it to a decent garage...and time is rarely available!!
Thanks

burnsa

peanut

burnsa the 944 cab is pretty airtight as you know. If you could smell oily smoke it must have come either through the heater or else from the EMU under the pas seat. Like you I am going to persevere with this because the car is not a pleasure to drive like this.

My 944 has just come back from the garage and it still has this problem. If you find a solution please let me know and I'll do the same for you
sound(at)solutionsuk.freeserve.co.uk
Nick

burnsa

peanut
Making some headway now. I did a thorough all round engine and luggage bin check today - and found the hose from the air deflector to the blower in eng comp was disconnected. Sorted that - simple (!) uni clip and working in tight space having to remove air pump hose to help access. Possibly the cause of oily smell, drawing eng comp air into heating system? My gues anyway. The car then started and idled pretty well for 20 odd minutes and did't appear to struggle - though I had charge up the battery, I cannot exclude fuel and/or alternator problem yet. My mate lent me a battery/alt checking 'thing' you stick in the ciggy lighter which made all the right noises and lights?
I will persevere and let you know...I would hate to miss another dry weekend with my head stuck in the wrong hole when I should be polluting the A1!!
Cheers
burnsa

johnchad

hi guys, been reading your posts with interest, the air control valve can stick and cause faults as you discripe, allthough it should not cause any strange smells inside (it looks as though you have cured that fault though) if you remove the valve it can be cleaned. hope this helps

burnsa

johnchad

many thanks for this - without getting the Haynes out where is the air control valve on a 911sc 81/82.

Once I've sorted this I'll get a beer...in Yorkshire if you insist!

Thanks

burnsa

peanut

Hi burnsa
sorry late response have not received any email thread subscription updates this week ?/??
Glad to hear you have a solution apparently.
My problem ,like yours , started after my car had been to the garage for a new clutch and cam belts. I reckon the garage must have left something lose or leaking or damaged something I'll check tomorrow.

Today I had the day off and I fixed my non opening drivers door and non working electric window
very satisfying to cure something by your own efforts.
keep in touch
peanut

burnsa

peanut
As and when I 'find' the air control valve I will let you know what happens.
Windows - mine stopped working last year, it was the relay that 'operated' both, but I had already dismantled the door cover and workings! Yes it's always good when something is cured.
Keep you posted as always!

burnsa

burnsa

peanut/johnchad et al
Good news I am happy to say!!
Not sure how this came about but my P car now functions properly!
Things I did which may be the curing factor:
On from the checks back end of March, I have changed battery (!I sometimes wondered about this and the power failure), WD-40 everthing vaguely electrical, checked air control valve and unit, cleaned air box and all sorts of crap from the hole, fixed minor wear & tear on various wiring looms including the sensor to the air pump and peripheral bits, fuses and relays all okay apart from one which needs gluing back together but is water tight so no prob there, and lastly dismantled all pipes to from tank in bonnet end and made sure no splits or crap in any part I could see.
So now it works and I don't what I did!!!
Thanks to you both for the patience and advice, and if and when I am in either West Country or Yorkshire - its my round!!
If either are doing Brands Hatch P fest in Aug - let's meet?
It's raining so I'll take it out anyway, have a good Easter
burnsa

peanut

Hi Burnsa Glad to hear yours is all sorted now. Obviously a result of your hard work and perseverence. A lot of us sit and think about all the little jobs we are going to do and thats as far as it gets!
I guess some electrical faults can be put down to gradually oxidising connectors going high resistance on wiring and relays etc and I'm sure vibration can eventually lead to some minor failures too.

I'm going to check mine over this w/e (My time will be shared between my new (1966) BSA A65 Thunderbolt and the pig)
I'll let you all know if I find the culpret for my self revving syndrome but anyway have a great weekend one and all
peanut