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S2 cutting out

zcacogp

New member
Chaps,

My much-loved S2 has just let me down. First (or worst) time in 12 years of ownership but it needs some attention. A solid diagnosis is what I lack at the moment so I'd really value suggestions.

- Car did a 50 minute journey fine.
- Stopped for about 45 minutes then set off for home.
- Car was idling in traffic and cut out - clean cut, no spluttering. It restarted fine, first time.
- 5 minutes later it cut out in traffic again. It re-started very reluctantly.
- 20 minutes later it cut out while doing around 45mph in 4th. Clean cut while driving (up a slight gradient) - I realised that the engine was providing no forward movement although the instruments looked fine. Changed down to 3rd and then 2nd to try and bump start it, it wouldn't play. Pulled over and tried to start it on the starter and it refused to catch.
- Waited around 15 minutes while I called the recovery people. Arranged to have a lorry sent and, just before I called off I tried the car. It started first time and drove home fine.

Now at home and it starts as it should. Clearly the thing needs sparks and fuel and compression so which one was lacking? For what it's worth, it's been very wet here but the car drove fine before cutting out, and I hadn't recently gone through any big puddles or anything like that.

The second time it cut out and restarted reluctantly it had the feel of something it has done before, which is to be hard to start sometimes when hot. It seems to almost catch but not quite, then starts but idles very lumpily indeed before dying. This time the lumpy idling sorted itself out and it ran properly.

Sadly, when it was stuck by the road and not starting at all I was alone and hence couldn't do any diagnostic tests (test for sparks, spray brake cleaner into the intake etc etc etc). I am therefore no further forward with knowing what it is.

All suggestions very welcome, thanks.


Oli.
 
Hi Oli,

I'd start out trying industrial quanities of WD40 (Other water disperal agents are available) over "things" electrical.

It doesn't sound like fuel pumps etc. just cutting out at 45mph.

HTH

Gerry

 
Gerry,

Thanks. The thing is that it ran fine during the journey when everything was soaking wet (it really was tipping it down). Then the weather cleared up, it stopped raining, the car was warm (warm enough to run the cooling fans for a minute or two) and soon after it stopped working.

I agree that a dicky fuel pump isn't top suspect when cuts at a steady 45mph but I'm not sure that the damp is to blame either.

The other suspect is the crank sensor, but I think that bounced OK when trying to start it.

DME relay? Maybe?

Thanks again for the suggestion.


Oli.
 
It's the intermittant nature of it that makes me think damp electrics. Relays tend either to function or NOT but something tracking down to earth with damp/water could be weakening the spark thendrying out and... Robert is your fathers brother.. as they say in yorkshire.
 
Hi Oli

I would defo go for a dme relay change they can do all sorts of funny things, If you want a spare i think i have 2 or 3


 
Gerry, yes, that's good logic. I guess my skepticism is that it worked nicely when wet and only failed when warm and dry. And the first time it cut out then it re-started just fine instantly. However at the moment I don't have anything concrete so won't discount it.

Martin, thanks, I have a spare DME and will swap it over. Although the only positive outcome will be that if it does break down again then I will know it hasn't worked .... :(

Thinking about it, when it cut out entirely while driving then the tachometer read a nice steady 3000rpm. This suggests that the crank sensor is working fine, so can be discounted. (Please let me know if this is assumption is wrong.)

Thanks again for your input Gerry and Martin.


Oli.
 
Rob, thanks. Notable thanks to Martin (Waylander) for his help by eMail as well.

Old DME out and replaced with the spare one. (Why I didn't think of this when stranded by the side of the road I'm not sure). It has just started fine with the replacement DME in place but then it wouldn't, wouldn't it?

Old DME re-flowed with a small soldering iron. All the connections work on the bench with an AVO tester.

Have I solved the problem? Dunno. Dare I drive it tomorrow? Dunno that either.


Oli.
 
I vote electrical as well. Based on your description Oli, I would check connection to the AFM first and then ignition switch second. I’ve chased around a number of electrical gremlins on mine and found it will run (in a fashion) with all sorts of sensors out of action or exotic fruit in places they dont belong but no AFM signal will stop it stone dead as will no connection at the ignition switch.
 
zcacogp said:
Rob, thanks. Notable thanks to Martin (Waylander) for his help by eMail as well.

Old DME out and replaced with the spare one. (Why I didn't think of this when stranded by the side of the road I'm not sure). It has just started fine with the replacement DME in place but then it wouldn't, wouldn't it?

Old DME re-flowed with a small soldering iron. All the connections work on the bench with an AVO tester.

Have I solved the problem? Dunno. Dare I drive it tomorrow? Dunno that either.


Oli.


Hey Oli,,
if you need side by Side by comparison then I am just back from Kent should you need any help,,,jasonp
 
Chaps,

Thanks for your answers.

Tom - thanks. Sadly I didn't get a pineapple with my failure although I will check the ignition connection and the AFM connection.

Roger, thanks. Any particular bits of the HT system that should be looked at or just take the dizzy cap off and check for tracking inside?

Jason - thanks very much, I am aware that we need to get together sometime soon! I fear that the bits of my car that are suspect will be hard to easily swap over but your offer is much appreciated, thank you. Maybe we should do a run in the country when it is working as it should be?

I didn't get much time today but did remove the fuel pump cover (first time off in my ownership) and discovered that it was FULL of crud. Black, wet gooey crud! The pump itself looked pretty happy inside it's foam sleeping bag and the contacts on the end looked sound but I'll remove and re-attach them to be sure. The banjo connection on the end of it is properly rusty though so I'll put some penetrant spray on it should I need to remove it in the near future. Next jobs are to check and clean the AFM and ignition connections (as suggested by Tom), look at the dizzy cap and rotor arm (as suggested by Roger) and possibly replace the fuel pump check valve (as suggested by Martin).

Thanks again chaps for your help. More updates as they come.


Oli.
 
A failed fuel pump check valve wouldn’t cause it to cut out while running. It just holds pressure in the fuel rail after the engine stops so if it fails it can make the car harder to start because the pump has to rebuild the pressure.
 
Tom,

That's what I thought as well, but I've just gone and ordered a replacement as it was indeed tricky to start sometimes when hot.


Oli.
 
The AFM signal wire could cause this as mentioned. I've had issues before with my old AFM. Been fine since I moved to MAF except got the MAF wet in a biblical storm and it done exactly as you described except was mostly dead and did not spring into life properly at any point. New MAF sensor fixed this. The similarity here is both AFM and MAF malfunctions means nonsense going down the AFM signal wire which means no start. Worth checking out. Could be as simple as a broken/breaking wire. I know on the turbo the AFM plug loom bends round backwards before the AFM and is a know point of failure. Not sure how the land lies on the S2 with that.

Stuart
 
Just going to throw this in, but as I'm as mechanically adept as a fish, possibly less so, it might mean nothing at all....

The instant cutting out is exactly what the car does when the FPR is failing. I've watched a 944 idling happily for 5 minutes after a long drive, and then stop dead as if the key had been turned off. Similarly, I've known reports of the engine cutting out when driving perfectly normally, without any other symptoms or pre-warning.
 
Chaps,

Thanks for the posts. There is an update: I checked everything that everyone suggested. So that's the following; changed the DME relay, checked the connection on the AFM (looked fine), removed dizzy cap and cleaned contacts using small brass brush on a dremel and cleaned it out with solvent, cleaned rotor arm, removed fuel pump cover and cleaned the crud out and checked the fuel pump connections.

I drove the car today - a short distance but in heavy traffic so it became nice and hot and the fan cut in a few times. And it behaved fine - didn't cut out (or show any signs of cutting out) once. It may be psychological but it seemed to run more smoothly and perhaps it started a little more strongly than usual. It certainly didn't do the half-hearted start-then-cut that it has done on occasions when hot (and I deliberately provoked it by stopping the engine and re-starting when it was hot, which are the conditions it normally happened in.)

This is perhaps even more annoying than before as I haven't diagnosed the problem and hence have no reassurance that it is fixed. It's promising but I guess I just need to drive it until it fails again, and if it doesn't then I just drive it some more. Thanks for your suggestions though.

Paul, Tom, thanks for the FPR suggestion. I changed that about 7 or 8 years ago so I'm hoping it's not that. It was about £40 back then, although ECP now show them for £430 - ouch! Having said that it looks like you can get them from Bulgaria for a whole lot less - just over £60 incl delivery here:

https://www.ebay.co.uk/itm/Regulateur-de-pression-AUDI-V8-Porsche-944-968-0280160287-94411019806-DS11108/152597008543?epid=1941531542&hash=item23877d909f:g:eek:w0AAOSwa~BYYm1f

It's made by DS (whom I have never heard of), not Bosch. I guess this is why it's cheaper. Have Bosch stopped making them?

Thanks again for your help chaps. I'll keep this updated if there is anything more to know.


Oli.
 
Mmm. I think I have a couple of 2.5 bar and a couple of 3 bar FPR's. Never realised they had become items of significant value! Think I paid £20 delivered for a good 2nd hand one a few years back when I had running issues. Can you not buy a good quality adjustable one for about £150?

Anyway hope your problem is solved Oli!

Stuart
 
FPR blimey they have to joking at £430!!

I got a 3.0bar one from Italy last year for £27.00 including postage, not bosch admittedly but it appears to work fine
 

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