Intermittent Fault.....Suggestions ?

[Frenchy]

Okay,
My 220 Turbo cut out 3 times when travelling up from Le Mans yesterday whilst just cruising at 75/80, pulled over knocked it off then restarted it then no problem until it happened again after say 150 miles.
DME realy is fairly new, car runs great before and after cutting out, started a couple of times today fine, mate at his garage reckons ignition amplifier,not sure the 86 turbo has one ? i know thw S2 does.

Any suggestions peeps ?

BTW we had 4 944's and 1 968 on our pitch at the LM Classic.............................Cheers Jim.

 

[George Elliott]

James, what was the cut-out like, was it a progressive stuttering or just CUT DEAD stop?

Did it just start on the button once the ignition was switched off / on again?

maybe a reaction to French air after so much of that Cumbrian stuff?

George
944t

 

[Frenchy]

Aye, good stuff up here George especialy when damp, in answer to your question, no fuss, no stuttering etc just engine stopped suddenly when cruising at a steady rate, started fine and ran okay immediatly after start up ???

 

[pauljmcnulty]

FPR?

 

[Frenchy]

Thanks for your suggestion Paul, let me know your thinking behind that, i do have a spare in the garage.

 

[pauljmcnulty]

ORIGINAL: Frenchy

Thanks for your suggestion Paul, let me know your thinking behind that, i do have a spare in the garage.

Only a lot of anecdotal evidence, I have no idea how it works! Random cutting out, totally unexpected, no stuttering etc., and then easily starting again has been reported as FPR so many times that I almost consider it as the new "dme relay" regular question.

I watched a car do this; it was idling whilst the guy tried to explain the way it cut out so suddenly, when after about five minutes it died as if a ghost had turned the key. He spent about £100 at a Bosche specialist to fix it.

 

[Frenchy]

Thanks Paul, i will change it and see if the car behaves itself ?

 

[peanut]

if it happens that infrequently perhaps it just might be a bad connection somewhere that is aggravated by a pot hole or bump in the road ?

 

[Frenchy]

Peanut, happening on smooth motorway, i can count that out as i would have noticed it. Paul FPR would probably cause stuttering before dying when i think about it, this is a dead stop with no warning and then it fires back up again and is fine.
Has anyone else got any suggestions as this is turning out to be a headscratcher ?

 

[peanut]

well if it occurred more frequently I would suggest replacing the DME relay with a 3x way bypass so that you can eliminate the DME relays and their respective earths and the ECU and its earth for the DME relay, injectors etc
Because it is so infrequent you could rig up a 3x way bypass and incorporate a SP ST switch between terminal 30 and the other 2x terminals 87 & 87b so that you can turn the fuel pump off without removing the bypass every time you turn the ignition off.

If it then runs without exhibiting the fault you will have narrowed down the search considerably

 

[pauljmcnulty]

Paul FPR would probably cause stuttering before dying when i think about it, this is a dead stop with no warning and then it fires back up again and is fine.

As I've said, that's exactly the reports that I've had many times, and witnessed myself. The car is working fine, then just stops dead as if the ignition was turned off. I'm not saying that's your problem, but it's worth checking it as it is a more commonly reported problem over the last few years. DME relays used to be asked about almost daily on Titanic 8 years ago, but they are almost all replaced now so less likely to be an issue.

 

[George Elliott]

if it happens that infrequently perhaps it just might be a bad connection somewhere

I agree strongly with this suggestion - given your description of the quite sudden cut, I would expect the cause is of an electrical nature.

Why would it happen? I can only suggest my theory:

I think your 220 leads a slightly sheltered life doing less than 10 miles per week per annum?
Joking aside, that damp air you refer to (we have in Ireland too, good dense stuff, excellent for engine efficiency) get into our cars and causes "invisable" corrosion - in this case on wiring loom connections.
In a daily driver, the motion of the car causes a degree of movement which causes the connections to rub and self clean and prevent high resistance occuring. A simple example of this is the horn slip ring on the steering wheel, look at a well used car and the horn sounds better too.
The Japs used to grease the electrical connection (as grease is an insulator) and they have a great track record for reliability.

My view is that you have a high resistance connection at a critical point, I am thinking of the 24pin ECU / footwell area of the engine management. Maybe the Flywheel sensor connections, AFM 5 pin connector. There is a build up of resistance, which leads to heat and further resistance and further heat and the unit eventually fails to receive the inputs it needs to function. When the ignition is switched, the unit resets, the recent memory is wiped, the poor connection is still there but not sufficiently poor to prevent running. HOWEVER, in a long motorway journey, the literally billions of signals exchanged in an hour at a 200 lepton cruise will accrue to a point where you see the problem.
There are folk on here who could explain why better than me because they understand the ignition and fuel adjustments being made in the ECU.

I had the same issue on an intermittent indicator bulb recently, corrosion build up, clean and grease, prob solved. But that is not a critical connection.

What would I do? - either gently clean and lightly oil the ECU harness connections and under bonnet connections to devices / sensors, and use the car more. I am sure use would fix it. If you know a bad road pay it a visit or drive on the cats eyes for a few miles.

What would I not do, dont start pulling a good car to bits when there is nothing wrong with the bits.

Good luck.
George
944t

 

[atticlab]

I had something similar on my 924S.
Engine cut completely on a motorway (also in France!). Refused to start initially and was towed off the motorway - however when we tried again it seemed to start/run OK.
..
Later has some seemingly unrelated electrical problems e.g. with sun roof etc. as well as occassional hesitation when starting.
It was eventually diagnosed to a corroded earth connection around the fuses/relays.

I perhaps should have suspected this earlier as I used to hear some relay chatter - which disappeared after the earth was fixed.

 

[peanut]

ORIGINAL: atticlab

I had something similar on my 924S.
Engine cut completely on a motorway (also in France!). Refused to start initially and was towed off the motorway - however when we tried again it seemed to start/run OK.
..
Later has some seemingly unrelated electrical problems e.g. with sun roof etc. as well as occassional hesitation when starting.
It was eventually diagnosed to a corroded earth connection around the fuses/relays.

I perhaps should have suspected this earlier as I used to hear some relay chatter - which disappeared after the earth was fixed.

the earths you refer to are critical earthing points for the DME relay and the ECU they are beside the underside of the fuse box under the dash and are MP2 and MP3 on the 944 schematic . Frequent source of hard starting and poor running but they are a pita to get to

 

[Frenchy]

Cheers Lads, i have wiring diagrams all main earths will get a good dose of cleaning and lubrication, the car is normally bombproof and gives no bother, mabe sulking as we were going home from LM []

 

[George Elliott]

I know someone with £100 for an early turbo with electrical issues[8|]

but hopefully they are sorted[]

George
944t

 

[GlennS]

My S2 did a few random cut outs, sometimes months apart, before finally throwing a snit and refusing to start at all one evening. Replacing the speed/reference sensor fixed it for me.

 

[alwigley]

Just a random thought that occurred to me the other day...... I frequently drive a house with a rather large radio mast attached and have noticed the engine stumble/hesitate when going past - I recall an early Mk 2 Vauxhall Cavalier (same year as my 944) my dad owned giving similar issues every time he drove by a radio transmittor in Croydon - this was one of the models fitted with a Hall sensor for the ignition, and we always wondered if this was EMF or similar interference with the Hall sensor. I know the 944 has a similar Bosch system, and wondered if any of our electrical/techie boffins (Barsk944 ?) could shed any light as this could be a potential cause of odd cutting out ?

Alternatively I could just be imagining it ! Will have to conduct a controlled test on the way home......

 

[Frenchy]

Cheers people, i will also take a look at the speed reference sensor, changed the main battery earth and i am in the process of working through the body earths, the car has not done many miles since but seems fine at the moment........................busy pulling the Turbo S to bits at the moment to give this some more time.