981 misfire

[David4780]

Hi, I have a 2014 981 Boxster with 45k miles. It was running fine but in the past few days the engine idle became rough, PDK changes aren’t progressive (sometimes holds a gear longer than normal) and PSM and Engine Control fault warnings came up.

A Porsche independent tech has diagnosed a misfire on cylinders 4,5 & 6.

The plugs were changed in line with the service schedule last year, but the Porsche independent are recommending new plugs, coil packs and cam shaft solenoids. Does this sound right?

TIA

 

[Motorhead]

Hi David,

I would think that since a whole bank of cylinders are misfiring the most likely problem will be an errant camshaft solenoid on that bank, and would suggest that as a starting point.

I can’t imagine that three plugs and/or coil packs would fail suddenly?

Jeff

 

[malarcy]

Sounds like the garage is wanting to fire a parts cannon at the problem to me.

I would expect them to be able to diagnose a little more accurately to be honest and coils and plugs can be tested by swapping side to side on one cylinder. If the fault moves then it’s the thing that moved causing it.

Internet guesswork at its best but I would start with actual codes , rather then the garages “interpretation”, if nothing specific shows there then a check of the wiring diagrams (someone will have one) for something common (I think those cylinders share an earth for the coils) then a cam position sensor would or the variocam solenoid on that bank as others have said

 

[ianthow]

I dou

Sounds like the garage is wanting to fire a parts cannon at the problem to me.

I would expect them to be able to diagnose a little more accurately to be honest and coils and plugs can be tested by swapping side to side on one cylinder. If the fault moves then it’s the thing that moved causing it.

Internet guesswork at its best but I would start with actual codes , rather then the garages “interpretation”, if nothing specific shows there then a check of the wiring diagrams (someone will have one) for something common (I think those cylinders share an earth for the coils) then a cam position sensor would or the variocam solenoid on that bank as others have said

I doubt if "the garage is wanting to fire a parts cannon at the problem". The diagnosis came from a "Porsche Independent tech", well what does that mean. A decent fault code reader will report exactly what this tech said. An OPC or proper Porsche specialist with more advanced diagnostics will be able to narrow this down by testing circuits and components. Yes, a single cylinder misfire can be attributed to the coil and/or plug by swapping however, if the fault doesn't move with the coil/plug, a more thorough investigation will be required to identify the cause.
With a misfire on all cylinders on one bank, the cam solenoid is the likely culprit. Take it to an OPC or a well established, Porsche specialist rather than shooting in the dark.

 

[malarcy]

Faced with misfire on 3 cylinders, putting plugs, coils and solenoid(s) on the car without narrowing the fault further, to me, sounds exactly like the garage is attempting to make the problem go away by changing multiple parts - i.e. firing a parts cannon at it.

As I said, and the same point you make, an appropriately skilled and equipped tech should be able to narrow the fault without shooting in the dark.

 

[BlackCab]

I agree with the first reply. I had a solenoid on Bank 1 go, giving me a misfire. The ECU sees the number of misfires accumulating and eventually you'll get the PSM warnings and finally it will go down to 4 cylinders. I made the mistake of only replacing one solenoid but a couple of months later I got the same problems on bank two. They are relatively cheap to change so I'd change both at the same time.

 

[David4780]

Thanks all for the comments. I took it to a different, very well regarded, Porsche specialist and they diagnosed the cam solenoid - which they see as a common fault.

I asked about getting both done but it was twice the cost (which makes sense being the same labour and parts on the other bank). They also said they don’t often see both go (which doesn't make as much sense but I’ll be happy if that is the case)

Looking forward to getting a healthy car back on Monday!

 

[JohnCRS]

Hi David. I had the same issue, advice and solution a few months back. 5000 miles later, so far so good.

 

[David4780]

Hi David. I had the same issue, advice and solution a few months back. 5000 miles later, so far so good.

Thanks John

 

[ianthow]

FYI, a 991.1 owning friend called me at the weekend for help diagnosing a misfire as the OPC could not 'fit him in until October!!' (and he has Porsche extended warranty!!).
He will be visiting them today with the fault diagnosis results (from my iCarsoft POR II tool).
From memory, this was:
1 Fuel rich on bank 1
2 Misfire Cyl 1
3 Misfire Cyl 2
4 Misfire Cyl 3
5 Bank 1 cam actuator fault
6 Excess intermittent misfires

Clearly the Variocam solenoid/actuator is at fault. I believe this problem is avoidable by ensuring that the oil quality remains good with annual oil and filter changes. The manufacturer's two year 'long life' change cycle may be fine for getting cars through the initial warranty period, but as the miles and years go by, normal engine wear will lead to increased rates of oil contamination, not catastrophic but sufficient to lead to problems with things like the variocam and/or hydraulic tappets.

Low annual milage is not an excuse to skimp on oil changes as lack of use is also not good for any engine; thin oil layers dry out and become sticky, internal condensation takes place, microscopic particles can settle out of the oil anywhere in the system, not just in the oil sump. All of these can cause problems.

For cars being laid up over winter, the optimum time for an oil change is immediately BEFORE laying up. After refilling, simply run the engine enough to circulate the clean oil and then rest easy.

My 90K miles 987.2, is used all year round and has been getting oil and filter changes since I acquired it at 48Kmile in 2015 (so just over 4K annually in my ownership). So far (touch wood) I have dodged tappet or cam actuator faults.