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Intermident Cutting out..

C

captainsmelly

New member
It's done this a couple of times now, just drive along, lose power (cant hear if it's missfiring because it's so bloody quiet and I'm a bit deaf) and engine dies. It will restart straight away on the key, although once or twice it was struggling to find a happy idle speed, bouncing between 400-1500 rpm felt like the air flow meter wasn't really metering the air flow.
Was especially bad on monday when it was pissing down - stopped about 10 times on a 15 mile journey.
What may be significant is that it mostly happens when driving up hills.. My journey on monday was a series of long climbs, and I had no problems coming back down again! I'm guessing water has got somewhere it shouldn't..?
Any ideas where to start?
Thanks
 
Stinky, Sounds like an odd one. It would be helpful to have a bit more info about the way it cuts out - whether it cuts out cleanly or whether it splutters before dying. Does the rev counter carry on showing engine speed once it has cut out? When did you last change the fuel filter? Oli.
 
Fuel filter was swapped recently - about 4 months ago As to how it cuts out, to make it more difficult to diagnose sometimes it kangaroos briefly, sometimes there's a split second where the engine is not firing and then it sorts itself out and sometimes it just has a severe loss of power. Rev counter - I haven't noticed anything out of the ordinary there, obviously it drops to 0 if the engine is stalled. What should I be looking out for?
 
Ah. Others on here will be able to be more help, but ... The 944 ECU takes a pulse from a flywheel sensor on the bellhousing, which tells it when to fire the coil. The rev counter takes it's reading from the same sensor. So, if the engine will turn over but not fire, one diagnostic is to look for a reading on the rev counter. If the rev counter shows signs of life (a 'twitch' while cranking, or a realistic looking reading while the engine is being driven 'round by the road wheels, in your case), then it indicates that the crank sensor is producing a reading correctly. Your step is to find out why it is cutting out; is it due to lack of fuel or lack of spark. Others will probably be able to help with some diagnostics on this (not helped by the fact that it happens while driving along.) Oli.
 
I'd look at the electrics - look under the bonnet when it is as dark as possible, looking closely at dizzy and leads then WD40 them! Cracked dizzy, damaged or worn rotor arm or old / damaged leads.
 
Our old friend the DME relay perhaps....? Without the car here I am only guessing but it might be worth putting a fuel pressure guage on the fuel rail - Put the guage under the wiper and take for a run..... that way when she misbehaves you will be able to see if the fuel pressure has dropped off .. If it drops its fuel related if it stays constant then its spark related
 
ORIGINAL: zcacogp Does the rev counter carry on showing engine speed once it has cut out? Oli.
Click to expand...
think you might be on the right track there Oli.If the rev counter drops during normal running and the engine hasn't stalled it could indicate the DME relay de-energising. If the DME relay de-energises during running you will lose the fuel pump and ignition spark. The problem is tracking down why the DME is de-energising. 1st I would remove the DME relay and put a 3x way cable bypass in the DME socket and run the car . If the problem goes away you know you have found the problem. Renew the DME relay may cure the problem then again the new relay may continue to randomly de-energise. 2nd I would be inclined to clean the main earthing points first. MPll and MPlll (Bad weather often aggravates poor connections .) 3rd I would check the battery connections and the connections to the ignition switch and DME relay socket Lastly I would try wiggling the crank sensor cables whilst the car is running and see what happens. The cables get brittle with age and heat and can breakdown intermitantly. The sensors rarely fail it is usually the cables. Good suggestion by vanhireboys too if you have a pressure guage handy. How much fuel in the tank ? some car's fuel pumps do not not pump well with low fuel levels in the tank .
 
Plenty of cases of fuel pressure regulator failing, leading to random engine cutting out. It's always been described to me as a clean, sudden total dying of the engine though, not with any warning or spluttering.
 
Pressure regulator is a good idea Paul - my old Lancia went, similar Bosch set up, would run for a bit then cough sand clutter revs all over the place sometimes stall, was that.
 
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