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Mis-fire Problem

Hope everyone had a good Christmas and a happy New Year to all.

I went to see the engine today which has now been dismantled. We have seen some evidence of damage to the crank block in the form of striations in the metal, as if something has gouged out some of the metal. I'll try and attach some photos dependent upon file size, to show enough detail to illustrate this.


We also noted that the composition of the two halves of the crank block were different in profile. That is to say that the block comprises alloy with steel inserts but the profile of the steel inserts differs between the two halves. The two halves are stamped with the same number "1173". Again I will attempt to attach photos to illustrate. Any comments as to whether the difference in the steel insert profiles are normal or not would be appreciated. There are also cracks between the alloy and steel sections appearing in some parts of the block. These should be evident in the photos.

Kind regards


John

AEE538FFFFEA46F19FB6B613C7DF52CD.jpg
 
ORIGINAL: Scouser

I've come into this late. But just read the entire thread. Surprised that nobody has mentioned cracked (or broken) cylinder liner.
My bets are that's exactly what your problem is. This has been discussed at length in the mags....specifically the autofarm writeup.
The engine seems to run fine, then it suddenly runs rough. When the engine is opened up a cracked cylinder is the cause and often a
piee (roughly the size you show) is cracked off the top of the liner.

I would call autofarm and discuss with them. Bear in mind that the cost of investigation and then refurbish may be more pricy that
just replaicing the engine with an already refurbished one......with guarantee too. I would defo consider taling to autofarm.
Click to expand...

Hi Scouser,

Thanks for the response and suggestion.

With the engine now dismantled, all cylinders have been inspected and are fine.

Kind regards


John
 
Hi Richard,

When I saw the engine last week I noticed some other gouging/grinding on another part. I went back today and took some shots of this part. We're not sure if this is problem-related damage or manufacturing marks. There are no broken spring valves or anything else that's been spotted as broken in the dismantling process.

Photos are attached for comment. The photos were taken from both ends of the other part in question and show marks at each end. I'm also wondering if the one half of the crank block (hope that's the right terminology) that shows the score/gouge marks and the cracks, fits into the other part shown in the latest photos and that somehow the damage in both is related. I also note that one of the latest photos shows the metal cracking/flaking.

Best regards


John



42B3A7B42C6748FC84FDE32C8B4C85DA.jpg
 
John

Those markings are really wierd. It doesnt seem like they are fettling marks to remove casting 'flash' as they are far too random and not neatly made, but the surface finish is what you would expect from that process. It isn't the sort of marking you would get with 'loose metal' floating about - you would also have seen evidence of that in the oil/filter. I have no idea how they could have been caused. The cracking looks serious too.

I'd give Porsche GB a call and see if they have anyone who would know.
 
Hi Richard,

Thanks for your comments. I'd had similar thoughts myself about the randomness of the marks. Iwould have expected any work done at the factory to be a lot neater.

DGR are being very supportive and are progressing the situation for me as they have some very good contacts in Stuttgart.

I did approach Porsche GB on 2 separate occasions about the problems but was told that I'd have to escalate the issue through an OPC. As DGR have a good relationship with the OPC I bought the car from, I'm using that route to get a Porsche expert to investigate/inspect the engine.

As yet nothing broken has been found in the dismantling process.

Best regards


John
 
Hi Richard,

I spoke to Customer Service at Porsche GB this afternoon. They said that any inspection that an official from Porsche GB would do, would need to be done at an OPC. As the engine's now fully dismantled at the specialist, this could be a challenge to get everything back to the OPC. Any experience with this sort of situation and is what they say correct/reasonable?

Rgds

John
 
John

No experience at all, I'm afraid, but I can understand that they want to see it at their workshop. Can't you make an appointment with them and load up the questionable parts of the crankcase in the boot and run them down there? I'm not sure they are going to be able to do much, as there is no warranty claim, but someone might be able to tell you if they have seen anything like it before. Maybe they employ Eastern Europeans in the foundry who aren't too worried about the appearance of their work. [:)]. If someone could give you an insight about what the markings are, if they are normal, and give you an opinion as to whether it's worth putting back together, it would give you some direction as to what to do next.

One of the problems is that there aren't many independents that have seen inside one of these engines, especially with the problems that you are having, so it's difficult to get answers. I somehow doubt that the OPC's have either, because all they do is replace them, and ship the faulty ones back to Stuttgart.

From a personal point of view, I'd be interested to know what the piston ring and valve guide wear was like. Do DGR have any views on this? Air-cooled 911 engines of that sort of mileage would probably need new rings and guides.
 
Hi Richard,

DGR have commented very positively and I've seen the cylinders, piston rings, valves etc. All look fine.

If you look on Dave's web site www.davegriffithsracing.co.uk you'll get a good idea of his background, pedigree and experience which are some of the main reasons why I went to him for normal servicing in the first place, not to mention proximity to my home and competitive pricing.

My earlier comments regarding inspection at the OPC were assuming this was normal practice as it seems reasonable to do so and on the basis that they would want to see the complete car. Dave can get the relevant or all engine parts back down to the OPC anyway.

To reflect your comments about independents and the number who have got down to the level of diassembly that Dave has, his experience with not only road-going but race car engines as well to this level, must put him in a fairly elite league.

As the car came with one year's warranty (even though it was the OPC's demonstrator) rather than the remainder of the Porsche 2 year warranty, if I had taken out the extended warranty as from the end of that 1st year, I would have paid out £2,175 to date. As I'd not had any other instances to call upon any extended warranty until now, I'm adopting an attitude that I've got that money "in the bank" as a starting point anyway.

Rgds


John
 
This may sound ridiculous (and I've never heard of it happening before), but is it possible that some tool or something was left in the crankcase at manufacture? It almost looks as if a screwdriver has spun round and gouged the bearing caps! Might also explain your chunk of metal found despite there being no chunks missing from the engine?

I am a graduate automotive engineer by the way, so this isn't a completely naive idea
 
Interesting thought Watty. Maybe even a bolt/nut/washer perhaps? Though I would have thought that something like that would have shown up very early in the engine's operation. It will be interesting to see if the metal fragment (more of a flake than a chunk) found in the sump could be matched up to some part showing the damage.

Rgds


John
 
Watty,
I acquired a nice Snap On screw driver when I was stripping my 944 Turbo (to turn it into a racecar), the screw driver had been left under the front passenger footwell sound proofing during manufacture!!!!
 
The markings in the second photo look like someone slipped with an angle grinder - it might be worth asking ~Autofarm about their experience of markings in the crankcase block, they have probably opened up enough engines by now for rebuilds/relinings that they would have a reasonable idea of whether such marks are factory or not, i personally can't see that Porsche would allow that sort of markings on casts, even if they are never to be seen.


Another option is Tech9 in Liverpool, who raced 996 and now 997 in the GT series - one of the head techs there (Chris ?) used to work for OPC Liverpool i believe
 
There are a lot of people familiar with the insides of a GT3 engine, as raced by Tech9, but I doubt if there are many who race an M.96. Agreed, Autofarm are probably the best bet for info, and maybe if Dave Griffiths knows them well they might impart it. They do tend to play their cards close to their chest - rightly, I suppose - as they have a business to protect. I assume that DGR hasn't pulled one apart before, otherwise he might have noticed similar strange markings. There is a 996 register outing to Autofarm on 27th, so we might get to see for ourselves.

There is a chap called Marcus London on this forum who races a Boxster. He might know whether the markings are normal.
 
On a positive note, Porsche GB have confirmed that after the car's fixed I can purchase Extended Warranty for 1 year before 125,000 miles subject to the car being inspected and passing the usual Extended Warranty inspection..

Rgds

John
 
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