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Porsche 991 - engine cut out - intermittent issue

Response from Porsche today is they can confirm the crank shaft position sensor was inspected for the spacer and all was ok. Not really sure what that means so if someone would like to explain I'd be grateful.

Thank you for the suggestion of the MAF - would the issue not be more frequent ?
 
Basically Porsche are saying they couldn,t find anything wrong with the CPS ( crank sensor ) .. the trouble is unless the car was running badly when they checked then theres no way of saying its ok .

I expect they tryed every way you described to get the car to run rough but it didnt hence they wouldn,t be able to find a faulty component .

Spacer refers to the correct gap between the sensor and the flywheel .. its about the magnetic strength generated by the flywheel teeth and the sensor .. too big a gap and you get a weak signal .

Its also a fix for a 996 turbo rev flair problem .. you fit a spacer .. didnt really work on that problem though but i digress :oops:

If the car runs fine then there is no problem to find and it doesnt matter what you test it will all test as ok.

Trust me faults like this are every mechanics nightmare .. ive had many over the years and have had to be honest with customers and just say drive it and see how it goes .. if it returns or becomes a constant problem then we can find it .

This is were fault codes help .. even if the fault isnt there it still gives us an indication of where to look and then make an educated guess .

MAF sensor .. always possible but i feel the PSM light / Maf load signal was corrupt due to just how bad it was running at that point ..

Mafs tend to be contaminated .. basically they give a false reading .. this will give an incorrect fueling but not Imho the type of fault the Op has .

Its more a constant thing with mafs .. granted the signal could drop out at the temps the fault occurs but a fault code would be generated and so far we have no codes to work on .

The PSM doesn,t care how bad the engine is running it just wants a signal which in this case would have been all over the place.

Its given up and said sod this im off down the beach untill you can give me something i can work with .. hence its shut down and taken the day off!

991 tend to be very good at generateing a code for even the smallest of deviations so a lack of codes means everything that can be tested by the car at that point is with in specs ... although it might be out of range at a given parameter.

Hence all my answers have been based on what i think could fail at high temps but not generate a fault code .
 
I forgot to thank you for your explanation before.

Not been using the car more than once per week for a 40min run each way to work, so I've not had much to provide an update.

Today the problem happened again. Engine fault light saying possible to drive on, plus PSM loss message, and start stop engine deactivated. Lots of engine shaking in 1st and second gear, then accelerate past it and the car appears to recover.

It was only high teens outside temperature wise, so that rules out the 30 degree heat as a factor
 
Further update, car reliably misfires after a 45 minute journey. One time I restarted the engine half a dozen times and it wouldn't idle for more than a couple of seconds and then stalled.

Leaving the car for 10 minute or longer and it fires back up and is ok albeit for a limited time. Also notice significant loss of power during misfire.

Given this new info, does this help provide any further clue as to where the fault may lie ? I'm going to take the car to the PC (i'll Break down on the way as it's over and he drive) and see about demonstrating the issue I guess now it's repeatable
 
Does my car have a DME relay ? Was telling my dad about the car problems and he read another Porsche owner had the exact same issue. That owner was advised it could be DME relay, DME sensor, or crank sensor. Sadly no follow up email to confirm fix.

Will follow up once car has been to PC. Thanks for listening and your help so far.
 
Dme relay problems are related to the earlier air cooled cars .. its a common problem hence most owners carry a spare.

There is not a relay like that as such .. rather several different electrical items .. there are various things i can think of that would cause your problem but with out any fault codes then not only would it take me ages to list it all out it wouldn,t help you.

As with any item it needs testing to see if its faulty and on a 991 then most of that is done with a tester connected.

You WILL have fault codes listed and that will lead anyone to what the fault is .

On the off chance they cant fix it ( which i very much doubt ) then give me a list of the codes found and ill add my 2 pennys worth to the problem :D
 
Thank you, at least it's not the DME relay then, although a cheap fix

I've managed to consistently replicate the fault with the car sat in the drive way. Leave engine running for 40 minutes or so, get in car, Rev to about 6k, take foot off the gas and the engine then stalls. After restarting the engine, it fires up idles for a second then stalls. This happens over and over, unless adding a bit of gas, Rev around 2k and the engine runs for a few seconds before the engine fault message displays, plus the usual PSM & auto stop start

Hoping the above will allow the PC to replicate while they have their diagnostics plugged in
 
Update: Porsche managed to read some fault codes today as I dropped
Off the car running rough. The codes show a misfire on bank 2, cylinders 4,5 and 6. The valve lift control was shown as a fault.

Porsche plan to swap over the valve solenoids for banks 1 and 2 and see if the misfire is then for cylinders 1,2 and 3.

I've had some good help here and wanted to keep you up to date in case it helps others.
 
Forgot to ask, if it is the valve solenoid, what's the likely labour and parts bill. ?
 
Hi lift valve solinoid bank 2 BUT i dont like the misfire on no 2 as normally you get just the bank of misfires .

I have a hunch about this but ill not bore you with it .. im good with what they are doing but to be honest i would just throw the bank 2 solinoid at it .

For any DIYers .. when you remove these solinoids then if ok no oil will come out .. if you DO get oil leaking out then its faulty .. i figured this out after ive done a few .

Ive probably seen 4 of these over the years so not huge but enough for me to think of this as an issue when answering here .

Ok labour time to replace . 1 hour .. parts cost im unsure of but ill guesstimate at £150.

Btw .. the fault is the high lift valve solinoid so the one in the center of the head and NOT the vario cam one.

EDIT ..

Just to explain if you didnt know but bank 1 is cyls 1,2 and 3 with bank 2 being cyls 4,5 and 6 .
 
Thanks for the reply. The misfire was just on cylinders 4,5 and 6 (bank 2) only.

Pleased to hear it's not the vario cam as I understand that part is expensive. Good to hear 1hr labour too.

Will let you know when there is new news
 
That's generous of you to offer money to a charity, though you'd already seen the fault pointed to the valve lift control in an earlier post so you were always going to be right 😁

Update: Porsche said today the cost is £230 to fit and replace the valve solenoid. I'm delighted to get the problem fixed for less than the cost of a tyre. It will be great to have a car that doesn't break down all the time too !
 

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