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Engine cut out. UPDATE

J

jetbox

PCGB Member
Member
After 3 years of trouble free running on my 2000my c4, today on the way home from work the engine just cutout. No warning lights or anything just lost power and cut out. I tried to restart and the engine just cranked but would not fire. I thought I remembered that leaving the ignition on for 1 minute reset the dme so I tried this. After a minute or so the car started fine and I drove of again.

About a mile later the same thing happened again. I left it a couple of minutes, switched ignition on and off and then it started fine and then behaved for the next 18 miles home.

Strange, no engine light and the engine revs and performs fine. I have a obd2 reader for vag cars so I tried that, with no engine fault codes being logged. Messed around at home and can not get it to do it again.

Searched the forum and the only similar case I can find appears to be a crank sensor problem. Is there a way to check this with obd2 or multimeter?

Any other ideas what it could be?

I am tempted to just try changing the crank sensor but some better ideas and more focused troubleshooting help would be better than just randomly fitting new parts.

Any help appreciated
 
Dodgy fuel perhaps?? I think it would be best to get a diagnostic check done with a Porsche tester, to see if there are any pending fault codes stored. Generic OBD2 code readers sometimes don't pick up the Porsche-specific codes.
 
thanks. I might need to invest in a durametric tool then. I have ordered a new crank sensor anyway as they are not that expensive.
 
Was the engine hotter than normal when it cut out? This happened to me last summer (on a very hot day and after some spirited driving).....it was as if I'd run out of fuel. After 10 minutes parked up cooling down the car ran as if nothing had happened. The previous owner reported this had happened once in his ownership too (with no fault codes). A trip to my Indy to use their PIWIS didn't show any fault codes at all (again).....so this year I decided to have the crank sensor replaced after various forums suggested this was a prime suspect. The clutch needed replacing and I had decided to replace the IMS bearing for a LN Engineering ceramic bearing whilst the clutch was out, so throwing in the crank sensor too seemed sensible.... I guess I won't know until the summer whether it's really fixed it or not....
 
The car was on the warm up phase a couple of miles after leaving work. Crank sensor arrived, ready to fit today. Time will tell....
 
well, fitted crank sensor and still the same.. then started to research the cam sensor. The car has two one on each bank but it appears only the left side one is used (unless my car is missing some bits of the engine loom??!!) so I swapped them over between left and right. not an easy job!! Anyway, car still the same. engine cuts out during warm up phase... think I need a durametric next. Anyone have one near to Aberdeen I could use?? Jetbox
 
Update. Well, went to start the car today and now it will not start at all. This is good in a strange way as at least I have the fault there permanently... Anyway what next. The book, the essential companion lists some fault finding. So far I have checked Fuses Dme relay Fuel pump relay Changed the crank sensor Changed the cam sensor It then lists Failed fuel pump Idle speed control valve stuck closed Throttle valve stuck open Resonance valve stuck open I am not sure how to check the last three? Any ideas?
 
Does it crank? If not, then it isthe immobiliser/alarm CU. If it does crank, then a diagnostic check would be the best starting point. You don't have an ICV on your car. If you take off the inlet hose to the throttle body you can see the throttle butterfly, but it is highly unlikely it has stuck. I don't think a resonance valve would stop it starting. I have never heard of anyone ever having a problem with one.
 
Hi, Has electrical power and the engine cranks over fine but will not fire. Richard, Do you have a copy of the wortkshop manual for the engine? i downloaded from cannel website but the second part of the engine manual is corrupt and can not be opened
 
Email sent. The workshop manual won't help, as there is no troubleshooting in it. The diagnostic manual may be of use, but without fault codes it will be difficult. What Alasdair says about fuel and spark is about as much as you can check without some diagnostic gear.
 
Update. Did some more fault finding tonight and it looks like its the fuel pump relay, I checked before and it was working but it looks like its hard failed now. If I jump pin 30 and 87 the car fires up fine. Resistance across the relay coil is high and out of spec. Only problem is there is not another relay the same to swap it with. I will need to order another one from Porsche.
 
ORIGINAL: A9XXC You can often open up a relay and at least check the contacts. Sometimes you can clean them up too!
Click to expand...
Hi Thanks, to be honest I did not even consider that... I have got a new one (£10 from Porsche) and will see if it does the job tonight. Jetbox
 
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