997.2 MISFIRE ON ALL 6 CYLINDERS

[liteuser]

I will apologise in advance if you have seen this post on other forums.

This issue is causing sleepless nights, and it seems no one has the same actual issue and answer.

I have a 997.2 2011 C4S
Has anyone had / heard of an issue where at 2300 to 3000RPM all 6 cylinders misfire? If so what's the remedy as it's an issue which at the moment can't be resolved on 5 vehicles that I know about, including my 911.

2 x 911
2 x Boxsters
1 x Caymen

All cars have gone in for a service and mine went in for a squeaking water pump change and slight oil leak.

Looking for any relevant answers from the obvious to the guru stuff.
So far,,,,, All plugs and coil packs changed, HP fuel pump, solenoids, fuel drained out and new fuel in, reset the adaptions,

TIA[/b]

 

[deMort]

I worked on one doing exactly this .. i never got to the bottom of it i'm afraid .. maybe with more time but unfortunately my garage charges by the hour ...

The one i worked on .. a reprogram of the dme would stop the fault for a while but then it would come back .. the misfires although all 6 are random amounts on each one ..

My theory .. the Dme is adapting to a signal that is basically incorrect .. i Found the ignition timing to be the one item that was out when compared to another vehicle ..

Im talking every possible engine value from every sensor here and just this one thing was incorrect ..

Obviously if the ignition timing is incorrect .. or shall we say at certain points in the rpm range incorrect then you will get misfires ..

My theory as to what's wrong .. something with the crank angle sensor or the wiring from it ..

Unfortunately that does include the flywheel as this is what the sensor looks at .

This job for me was a failure as in i couldn,t fix it and lets just say .. i was on a severe downer for several weeks afterwards ..

Failure isn't pleasant .


EDIT ...

Very interesting you had a water pump replacement ..

The car i worked on had a water pump failure and the fault seemed to have started after this ..

My one was leaking so i did consider water in a wiring loom but couldn't find anything .. did yours get water sprayed anywhere or was it just replaced ?

 

[Robertb]

It's a long shot, but could it be an issue triggered by the immobiliser... I had a similar fault many moons ago on a car caused by this.

Or could it be E10 fuel??

 

[deMort]

Normally i don't answer when people post .. but as i'd love to get to the bottom of this i'm making an exception ..

Nice ideas , the fuel on the above car has been replaced but there's nothing to say its not E10 as opposed to E5 .. for the car , certainly worth adding just to prove .. it would fit in with my reprogram and the car is adapting to something ..

Immobiliser .. that would be the factory one and i'm unsure how it could cause this .. car either starts or doesn't with an immobiliser fault .. once the key transponder has been read and identified it will start and is no longer active until key out of the ignition .

More ideas please .. this has been on my mind for many months now .. just having suggestions actually helps me a lot .. it's like talking to someone at work .. something suddenly jogs the memory .. makes sense and off we go !!!

No offence intended .

 

[Ronyted]

Just a thought, would a dyno run in the hands of someone who understands and can interpret the data he's looking at highlight any rogue DME adaptions?

 

[Robertb]

Are these all DFI cars?

 

[deMort]

yes .. only DFI cars ..

Dyno .. they can look at the values but so can i .. only the timing seems to be incorrect .. ignition timing that is .. its a possibility though so thank you .

I'm struggling to see how a crank angle sensor could give an incorrect signal .. basically too slow .

It's about 10 degrees out .. yup i know it could be replaced but the car i had has had so many parts replaced with nothing making a difference i'm unsure in just chucking yet another item on it ..

hence ANY help from here would help ... just say what you think .. i don't care .. for me .. its something i need to get to the bottom of and have not been able to .. disappointed in myself atm so just talking to people helps .

 

[liteuser]

The input so far has been amazing, thank you so much.....

The water pump was making a chirp/squeak and it had a small oil leak on the sump.
They replaced the water pump with a Porsche part and an Aux belt too.
This is the point when the timing issue started.
They fitted another water pump as they thought the new water pump was faulty as under a strobe they could see it was oscillating and had a vibration.. The car has done 35000 miles.
Coil packs, spark plugs, hp fuel pump, solenoids, variable oil pressure sensor, pulleys, tensioners and more have been replaced, along with 40 hours of labour. It's been taken to Porsche Norwich and had the ecu flashed / updated, which did resolve the issue,,,, temporarily.... and then it came back.
I think I was told that it runs with out the belt on but as soon as the belt is fitted the misfire comes back.
Is there any questions you would like me to ask them which may help?
I'm going to pop in for a coffee and an update.

I really am grateful for everyone's time and input.. please keep the suggestions coming.

thank you

 

[T8]

......... It's been taken to Porsche Norwich and had the ecu flashed / updated, which did resolve the issue,,,, temporarily.... and then it came back.

I'm an absolute technoduffer but to my mind that points to an ECU problem. :dont know:

 

[deMort]

I have a working theory now , ill update tonight when at home .

 

[liteuser]

I have a working theory now , ill update tonight when at home .

Appreciate your information and you dedication to resolve this issue.
Just to say the fuel has been drained and it was Tesco super 99. £60 of Fresh Shell fuel, super unleaded E5 has been put in.

The engine is coming out, 10 hour job, to replace the crank sensor which is ceased, while at this stage is there anything else they can check/replace?

 

[deMort]

The info you have supplied has helped immensely i must say , the car i worked on with this issue and i was the 3rd garage to look at it.

Many , many parts had been replaced , i was told about the water pump failing and this issue starting around that time .. I considered water in the wiring , technically you could stick the loom underwater and not have issues but i did consider it but found no issues ..

I discounted the water pump after that as after all .. it just pumps water .. how the hell could that make any difference ... Actually it does .

Bit more on that later ...

Sooo my car .. if i slowly increased the revs from 2 k to about 2600 - 2800 rpm and whilst holding the throttle steady the revs dropped back to about 2100 rpm .. the throttle was in the same place .. it's about now the real misfires started and an eml came on .

I checked the throttle .. i was at say 20 % when this rolled back .. I'm now at a throttle opening of say 20% which was 2800 but now at a much lower rpm 2100 rpm .

Be worth your garage doing the same slow increase on the throttle .. and i mean slow to see if they get the same roll back .. kinda important as that conforms we do have the same issue and my theory as to what's going on is possible .


Both cars had a new water pump and the fault started then ..


Your car and the pump was oscillating , they replaced it , im guessing its still doing it ..

You car as you have said twice doesn't misfire if the drive belt is not fitted .

An analogy of oscillating .... you have a wheel out of balance .. you drive the car around town and you would never know .. get onto a fast road and at 61 mph the steering wheel starts to shake .. go faster and at say 75 the steering will stop shaking ..

This as best as i understand it is Harmonic Vibration , a moving object creates a frequency .. as it spins faster it will reach the natural frequency of an object to vibrate .. hence the wheel has a frequency of 61 mph in terms of rotation and the imbalance of the wheel reaches that frequency and causes the wheel to shake or Vibrate to be correct .

Im struggling with how to describe frequency based vibrations here so if any experts want to put it into layman's terms i would be grateful .

Ok so what has this got to do with the issue on both cars ...

A vibration is what .

This ain't a wheel shake .. it's more subtle than that but it is something that's causing a timing issue on all 6 cylinders which at 2700 - 2800 is at its maximum effect .. the frequency vibration matches that of the component at this point .

That's not a crank angle sensor .. that's static .. what else do we have that can affect ignition timing ...



The Dam Knock sensors !!!

They are looking for pinking ( a noise ) .. when they see it they roll back the timing by 6 degrees on EACH cylinder

As there is no knock they are reacting to a false signal ( a frequency , vibration call it what you like but they are resonating ) and the timing for every cylinder will be retarded when it shouldn't be .. i have no idea of the max retardation but even at 6 degrees that would cause a misfire and with this .. that's all 6 ... 2800 rpm .. max resonance !

A knock sensor is in effect a piezo crystal , compression causes a voltage .. you can scope these .. i have in the past but the signal is just junk so scoping wont prove this .

Perhaps unplugging x1 knock sensor , belt on and seeing if the misfires are one bank only ?

Now then .. i looked at the knock sensor retardation for every cylinder on my car .. nothing .. there is no adaptions list for this but perhaps there is but not shown on a tester ..

We both reprogram the dme and it was fine for a while .. until the car adapted to something .. i'm guessing there might be a hidden adaption map for the knock sensors .

It's also possible the tester i was using cant react quick enough to show the retardation in real time .. its too quick basically .. the testers we use only every give a snapshot of a value .. when something happens for a few milliseconds the tester might not display it as it takes an average value .. i don't know there .

So what's the fault .. both of these started after a water pump , your one was oscillating and might still be ..

For me .. water pump is still an issue ..

Drive belt tensioner .. i'm thinking the shock has an issue after belt replacement ..

The drive belt .. maybe too tight perhaps ..

Difficult to find especially when you replace a component , that does not fix it so you move on ...

I have fitted the same as your garage components in the past that have been defective from new .. it then becomes a major issue as we think its fine and move away from it ..

In this instance .. it's something to do with the water pump replacement .. that's my opinion anyways .


I'll also add .. i rarely get beaten by any fault on a car .. this one had me at my limits as it just didn't make sense .. i'm pretty sure no garage yet has fixed this issue ..

5 Cars you said you know of .. we Must get to the bottom of this somehow hence i've given everything i can think of to help you and your garage .

Yup i know they won't listen to a forum warrior , garages don't but i explained that in pm .. if they don't listen to what i have to say then i can't help any further .

 

[P9XX]

My thoughts for misfiring on all 6 cylinders are as follows.

Probably not new coil packs if either Porsche OEM ,Beru or Bosch fitted.
The coil packs can individually report back to the ECU if a misfire occured, bit all 6, I think not.

The Crank Position Sensor can also report a misfire if it doesn't know the crank position. In conjunction with the cam position sensors, it will make a best guess which cylinder misfired. Leading to all cylinders being reported over time I guess.

There are a number of sensors which feed the ECU with data which is used to control the amount of fuel going through the fuel injectors. A faulty water temperature sender or the ambient air temperature sensor built into the Mass Airflow Sensor could possibly influence fuelling /misfiring.
Oil contamination of the MAF is not too likely at your engine mileage.
Does the water temperature gauge run around 80c reliably when hot?

Finally, on things to check, is the engine earth strap in good condition and making good contact at both ends.

Hope it gets sorted soon.

 

[liteuser]

Thank you both Demort and P9xx I really do appreciate your information.

A new Oem water pump was fitted, as the existing one was chirping/whimpering at idle/tick over. They noticed the replacement had a vibration when working and had the misfire issue.... Finger pointed to the new water pump so they replaced that with another new OEM water pump, which had a slightly less vibration......that water pump os still fitted and then it feels like we are running around in a rabbit warren🤦"â™‚️🤦"â™‚️

The misfiring and the AUX belt are connected, how I don't know, when the AUX belt is removed from the car there is no misfire issue.

Im going to relay the information back to my Indy.
I will definitely keep you updated on here or by PM

 

[liteuser]

:?: