Intermittent total loss of power

[uk_sub]

Hi All,
On my way home from the R17 Concours @ Highcliffe today (wonderful day if you weren't there) my car suddenly lost all power (I can only describe it as being like what happens on my scooter if you've forgotten to turn the fuel tap on)...3 seconds later and it burst back into life. Luckily it only started doing this about 2 miles from home and I managed to limp home (much to the annoyance, and maybe amusement, of the following traffic that had to put up with me flashing hazards to indicate I was pulling over and a few seconds later the car would leap up the road like nothing had happened.
It must have done this about 20 times in all...

It was very hot today and interestingly the previous owner reported the car had done the same thing about 3 years ago, again on a very hot day (it went into the local OPC at the time who could find nothing wrong).

The only gauge that was different to normal was the voltmeter....this usually sits just under 14v but was unusually lower reading 12v. Made me wonder about the alternator or diode pack but not sure if a fault in this area would give these symptoms.

There is no CEL so I guess a diagnostic readout will reveal nothing....

Any ideas?
Stuart

 

[Richard_Hamilton]

Depending on the MY of your car, the CEL does not always come on when a fault is recorded, so it is worth checking that first.

 

[uk_sub]

Hi Richard,
It's MY1999, I'll see about interrogating the fault codes to see if anything's been logged.....the fact you haven't immediately had anything spring to mind is a bit worrying though

 

[Richard_Hamilton]

Very difficult, as I haven't heard of this before. My hunch would be a fuelling problem, but I'm just guessing.

On a UK MY99 C2, the CEL will only come on for a serious emissions issue. You also need a Porsche tester to read the fault memory properly as the 'pending' codes are stored in a separate register which isn't accessible with an OBD2 scanner.

 

[chriscoates81]

Do you think it could be the maf richard? I had a similar problem when i had a corsa last year and it was due to the seal going on the maf and letting mositure in, when the fault happen all the power went (all 90hp of it[]) and it went into a limp mode. Of course im assuming a 911 has a maf as well i dont know that much about the cars.

 

[uk_sub]

I've recently replaced the MAF sensor but of course all the cabling to it has remainded....hoping the Porsche tester will show up something in the log (won't get a chance to get it to the indy until next w/e now though)

 

[tim92gts]

Is the a/c working ok?
On the 928 and some Jags the return a/c line cools the fuel.
Bit of a long shot but thought it worth a mention.

Tim
03 C2Cab
92 928 gts

 

[AlexBell]

The MAF would certainly give a CEL, I'm just guessing but since you have a low volt reading maybe your battery or alternator isn't working right. This wouldn't give a fault code I think.

 

[Richard_Hamilton]

A faulty MAF will not throw a CEL on a UK 1999 C2. A dodgy alternator or vattery may record a low voltage as a fault in one module or another.

 

[uk_sub]

Well....eventually got home from working in Germany and found time to take it to my local specialist. No faults logged at all (as i suspected would be the case as this is what happened to the previous owner a few years back).

After driving there (it was nice and sunny, but not as hot as the day it played up) and leaving it running in the workshop for a while to get everything to max temp we still couldn't invoke a problem.

Stuck for ideas now (short of waiting for a more permanent failure).

Car has run like a dream since the day it exhibited the 'fuel loss' symptoms (34 mpg).

It sounds like the MAF but i've changed this....i'd have thought a bad connection to the MAF would have thrown some sort of fault.

Baffled!